# class a/b vs class D



## Mat Dope (Jan 3, 2007)

i searched and didnt find much about this.

just wonder for a sub amp is there actually a difference that you can hear and that affects SQ and mechanically is their actually a difference. i know in terms of efficancy but what else.


and sorry if this has been beat to death i didnt find much.


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## bobditts (Jul 19, 2006)

I remember seeing a few discussions about this already but cant remember how they started. Basically there are no audible differences for the most part. some people will give their opinions. There have been many SQ winners using the full range class D technology if that means anything to you. I am running the eclipse version myself and I love it.


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## 60ndown (Feb 8, 2007)

Mat Dope said:


> i searched and didnt find much about this.
> 
> just wonder for a sub amp is there actually a difference that you can hear and that affects SQ and mechanically is their actually a difference. i know in terms of efficancy but what else.
> 
> ...


class a/b sounds better than class d on my sub, no question.


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## 89grand (Nov 23, 2006)

I run both. A class A/B A600.2 in my Jeep and a class D GTO 600.1 in my Crown Vic. I can't tell the difference between them.


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## raamaudio (May 4, 2005)

Oh boy, here we go again, another war on sub amps.

I am an A/Ber and have tried far to many configurations and thus will never run a D class sub amp again

Rick


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## Diru (May 23, 2006)

A good class A/B will take you down to below 10hz, were a class D will most likely choke. 

What does a class D have 9.9xouta10, yep , infarsonic filters. 

Otherwise the eff in the 80%+ is nice with big power.

Full range D, got nothing to say......


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## t3sn4f2 (Jan 3, 2007)

Multi thousand dollar audiophile grade home subs built for stereo reproduction reviews as sounding excellent all the time use class D amps. Thats all I need to point me in the class D direction.


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## raamaudio (May 4, 2005)

That had nothing to do with reality, the vast majority of high end home audio is 10x overpriced and over hyped and yes, I have listened to a great deal of it

I have been grossly underwhelmed by nearly all the high end home audio gear I have heard over the years.

Big bucks sub systems may of had big bucks spent on really getting the most out of D class amps though, optimized for the drivers used, etc, etc, etc, really not comparable to what we do in our vehicles.

Rick


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## t3sn4f2 (Jan 3, 2007)

raamaudio said:


> That had nothing to do with reality, the vast majority of high end home audio is 10x overpriced and over hyped and yes, I have listened to a great deal of it
> 
> I have been grossly underwhelmed by nearly all the high end home audio gear I have heard over the years.
> 
> ...


You have a point, but I still think class D is more then sufficient for car audio.


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## raamaudio (May 4, 2005)

If your subs are burried in the trunk, never heard a setup like that I liked, ported or whatever, then a D amp may be just fine. If you have a proper IB setup(my favorite for a sedan) or sealed in a hatch, etc I would want an AB amp. 

I have tried to love D amps, I have owned many, I always go back to AB.

Rick


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## t3sn4f2 (Jan 3, 2007)

raamaudio said:


> If your subs are burried in the trunk, never heard a setup like that I liked, ported or whatever, then a D amp may be just fine. If you have a proper IB setup(my favorite for a sedan) or sealed in a hatch, etc I would want an AB amp.
> 
> I have tried to love D amps, I have owned many, I always go back to AB.
> 
> Rick


You are making me question my outlook on things . Nope, you will not defeat me   .


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## bobditts (Jul 19, 2006)

I had my 15" IB on an A/B amp and it sounds exactly the same as it is now on my ICEpower class D amp. although, I could be tonedeaf for all I know lol


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## DS-21 (Apr 16, 2005)

If you are running a subwoofer system that's so inefficient (one might go so far as to say "badly designed") that it requires megawatts to get going, then Class D is a better choice just because the demands on your car's charging system will be less.

If you're running a typical subwoofer system, no difference.


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## Mat Dope (Jan 3, 2007)

ok thanks guys, just wondering. im running class D right now for my sub and honestly sounds but just wondering what i was missing if anything. i think this is one of those ported vs sealed SQ wise type things...


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## cvjoint (Mar 10, 2006)

I've run several Class D amps before, even from the same maker and the difference from A/B was very perceiveable to me. Will not run Class D again, it sounds a bit soft and from a lack of verbiage retarded...quite slow on reproducing music. The A/B shines on bass attacks, and I don't know whether it is from a difference in amp. class per se or a general Class D manufacturing technique (filtering and the like) as Rick mentioned.


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## bassfromspace (Jun 28, 2016)

Seriously, have you guy's looked at the THD on a GREAT sub while playing? We're talking upwards of 20%. If you can hear the difference between the two topologies, I want some of what you're toking ASAP.


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## kappa546 (Apr 11, 2005)

class a/b for me. i've run many class d sub amps and i definitely think theres a difference. i havent used a fullrange class d tho


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## autofile (Oct 25, 2005)

Why settle, when you could have the best of both worlds: Class G!

Class G is actually class A/B output, but with multiple power rails designed in the power supply, which increases the efficiency dramatically, to nearly that of a class D design (nearly 80% according to CA&E test reports) but with the superb sound quality reproduction of conventional Class A/B, or in some cases Class A, designs.
Truly the best of both worlds!


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## audiorailroad (Mar 6, 2007)

autofile said:


> Why settle, when you could have the best of both worlds: Class G!
> 
> Class G is actually class A/B output, but with multiple power rails designed in the power supply, which increases the efficiency dramatically, to nearly that of a class D design (nearly 80% according to CA&E test reports) but with the superb sound quality reproduction of conventional Class A/B, or in some cases Class A, designs.
> Truly the best of both worlds!


how many class g amps are available?


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## cvjoint (Mar 10, 2006)

I found this to be very interesting read and in tune with my experience so far:

"Class G and H amplifiers add complexity to the signal and degrade it because of the need for switching depending on the input signal 
Class D amplifiers are models of efficiency, but with a loss of detail and fidelity 
Class B amplifiers generally introduce some crossover distortion, but move away from Class D, G, and H's extreme non-linearity. 
Class AB amplifiers may introduce some crossover distortion, but they get closer to the ideal of Class A for most of its operating regime. They are indeed the best compromise of performance versus cost. 
Class A amplifiers introduce no crossover distortion and are the most desirable amps to own, but they are expensive, run hot, and have to be very well-built. "

http://stereos.about.com/od/homestereotechnologies/a/amp_op_classes_3.htm

I'd love to get my hands on a class A design.


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## 300Z (Mar 20, 2005)

To those who claim that one is better than the other, that hear differences between amp topology's, What do you think is the cause, what kind of difference is there?
Just wondering... For now...


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## t3sn4f2 (Jan 3, 2007)

Oh Oh, I feel the thread transforming once again. RUN! Don’t get drawn into a pointless debate AGAIN.


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## ca90ss (Jul 2, 2005)

300Z said:


> To those who claim that one is better than the other, that hear differences between amp topology's, What do you think is the cause, what kind of difference is there?
> Just wondering... For now...


x2

Lets look at what differences cause amps to sound differently:

#1. gain (pretty easy to change)
#2. frequency response (most class d amps have response out to at least 300hz which is plenty for subwoofer use and any differences in response should be easily fixable with an equalizer)
#3. power (for the sake of this argument not important)
#4. noise (not caused by amp topology)
#5. distortion (a 1% difference when the subwoofer is producing 20% by itself is negligible at best)

So I would like to know what other factors are causing the huge difference some of you are claiming?


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## 300Z (Mar 20, 2005)

t3sn4f2 said:


> RUN! Don’t get drawn into a pointless debate AGAIN.


Quite the contrary, I hope it becomes more of a educational thread than instead leaving the so called differences to be attributed to some "voodoo magic"?  

Leo


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## t3sn4f2 (Jan 3, 2007)

300Z said:


> Quite the contrary, I hope it becomes more of a educational thread than instead leaving the so called differences to be attributed to some "voodoo magic"?
> 
> Leo


Good luck to you


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## kappa546 (Apr 11, 2005)

it's been a while since i've run a class d. i switched from a much more powerful class D to a decent class a/b (so you can throw the power/gain difference out) and the difference was very profound. the class a/b although putting out almost half the power seemed almost every bit as loud as the class d (no idea why). bass seemed tighter, quicker, played lower cleanly, was less localizable, the impact was stronger and composed.


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## kyheng (Jan 31, 2007)

My understanding of class D amps is its stabilities on going low independence, I would be wrong, but as far as I see, other than class D amps, others can go to 2 ohm(class A, B, AB)

OT : Anyway, my sub amp's fuse rating are 120amp and I lay direct cable to it with a 60amp fuse near to my battery, it is sufficient enough or can cause any trouble? As last time the fuse rating was 40amp and blown few days back.


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## phatredpt (Feb 22, 2006)

Doesn't class D get a little ugly (more so than class A/B) when pushed to clipping also?
Not that you should be running there by any means... 

Sticking with power sucking A/B goodness myself!


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## ca90ss (Jul 2, 2005)

I don't doubt that some of you hear differences. I'm asking what these differences are attributed to (gain, frequency response, power, noise or distortion).


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## cvjoint (Mar 10, 2006)

kappa546 said:


> it's been a while since i've run a class d. i switched from a much more powerful class D to a decent class a/b (so you can throw the power/gain difference out) and the difference was very profound. the class a/b although putting out almost half the power seemed almost every bit as loud as the class d (no idea why). bass seemed tighter, quicker, played lower cleanly, was less localizable, the impact was stronger and composed.


Exactly what Kappa546 said this is exactly the difference I've bumped into. FWIW I could be running 5 polk monoblocks as opposed to the 5 two-channel class A/B amps and run a smaller footprint, more wattage, and drain less power. In practice the 2 channels sound far better even though they have been benched to make at least 50w less than the monoblock version. 

Other people run the arc 2500xxk as opposed to the mono class D version for the same reasons. Why does A/B sound better? Beats me...


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## Neil (Dec 9, 2005)

The question, ultimately, is can you prove it? In a double blind ABX test, can you pick out the class a/b amplifier beyond reasonable doubt? And the answer, in my experiences, has always been no.

It's so funny that the reason home audio is most criticized is because of the voodoo magic and golden ear philosophy, and yet that's the same thing being claimed here.

The topology of the amplifier is the absolute last thing I look at when picking out products.



kappa546 said:


> it's been a while since i've run a class d. i switched from a much more powerful class D to a decent class a/b (so you can throw the power/gain difference out) and the difference was very profound. the class a/b although putting out almost half the power seemed almost every bit as loud as the class d (no idea why). bass seemed tighter, quicker, played lower cleanly, was less localizable, the impact was stronger and composed.


That could very easily be attributed to power compression.


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## DS-21 (Apr 16, 2005)

audiorailroad said:


> how many class g amps are available?


For the car, I don't know. Since Peter posted, one would assume Genesis. 

For home, NHT, Outlaw, and Sunfire sell them. Bob Carver claims credit for inventing the topology, though I have no idea if that's truth or propaganda. I will use a pair of NHT A1 monoblocs (their Class G amp) to drive my main sub for another week or two. (I ordered a Crown XTi2000 to take over for it earlier today.) They sound just one would expect a good Class AB or Class D or Class H for that matter Class A amp capable of 200W/8ohms and 300W/4ohms to sound in that role and as full-range amps.

What's theoretically better than all of the above classes is direct PCM->PWM conversion, but either TI (who bought one such technology from TacT and sells it under the name PurePath) has had huge amounts of trouble getting it to work at low impedances, or there's just not that much interest in true SOTA unless it's also ultra-cheap. Probably a little of both.


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## thehatedguy (May 4, 2007)

Genesis and Rockford Fosgate are Class G. Those are the only 2 that comes to mind for the car.


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## thehatedguy (May 4, 2007)

From the Rane site:

Class G operation involves changing the power supply voltage from a lower level to a higher level when larger output swings are required. There have been several ways to do this. The simplest involves a single class AB output stage that is connected to two power supply rails by a diode, or a transistor switch. The design is such that for most musical program material, the output stage is connected to the lower supply voltage, and automatically switches to the higher rails for large signal peaks [thus the nickname rail-switcher]. Another approach uses two class AB output stages, each connected to a different power supply voltage, with the magnitude of the input signal determining the signal path. Using two power supplies improves efficiency enough to allow significantly more power for a given size and weight. Class G is common for pro audio designs.

[Historical note: Hitachi is credited with popularizing class G designs with their 1977 Dynaharmony HMA 8300 power amplifier, however it is shown much older by GRS: "Class G - I have been searching for the proper inventor of this class, but have not been able to find a reference older than 1965 when I first encountered it in a college text "Handbook of Basic Transistor Circuits and Measurements" by Thornton et al., SEEC vol. 7. The method is introduced without references or fanfare. One is led to believe that it was common knowledge in 1965 and earlier. This is not the first known use of extended quasi-linear methods (beyond class B), as there is a dual found in Fisher U.S. 2,379,513 from 1942."]

Class H operation takes the class G design one step further and actually modulates the higher power supply voltage by the input signal. This allows the power supply to track the audio input and provide just enough voltage for optimum operation of the output devices [thus the nickname rail-tracker or tracking power amplifier]. The efficiency of class H is comparable to class G designs.

[Historical note: Soundcraftsmen is credited with popularizing class H designs with their 1977 Vari-proportional MA5002 power amplifier, however like class H above GRS finds precedence: "Class H - The apparent inventor of class-H in full-blown multi-level form was Manuel Kramer of NASA in 1964 U.S. patent 3,319,175. Class H optimally applied to a full-bridge was invented in 1987 (Stanley) U.S. 4,788,452. Classes G and H are all members of a class of amplifiers that has articulated rail voltages to improve the efficiency of class B power stages. Examples are available of tracking using binarily weighted segments, (Stanley) U.S. 5,045,990. Continuously variable tracking with switch-mode PWM appears to have been first done by Hamada in 1976 U.S. 4,054,843. The ultimate rail tracker using interleaved technology is found in (Stanley) U.S. 5,513,094. Only with interleave is the converter fast enough to meet the needs of full-bandwidth audio and yet have low switching losses."]


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## MarkZ (Dec 5, 2005)

DS-21 said:


> For the car, I don't know. Since Peter posted, one would assume Genesis.
> 
> For home, NHT, Outlaw, and Sunfire sell them. Bob Carver claims credit for inventing the topology, though I have no idea if that's truth or propaganda.


According to Doug Self...

"The history of Class-G amplifiers goes back a long way. The earliest reference I am aware of is an article in Radio-Electronics, dated August 1976. Hitachi is credited with putting the first Class-G design into production- their 1977 Dynaharmony HMA 8300 power amplifier."

http://www.dself.dsl.pipex.com/ampins/classg/g.htm

Edit: ah, thehatedguy beat me to it.


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## durwood (Mar 7, 2007)

> Class D amplifiers are models of efficiency, but with a loss of detail and fidelity


For D class,
I always thought they sounded thin and unnatural-although I have heard A/B amps sound similar. Distortion was never an issue. They are clean, almost too clean. It's like if you walk into a room that is completely silent, doesn't that drive you nuts? 

Good A/B forever.


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## chad (Jun 30, 2005)

Before we get into a numbers=numbers debate and clinical test bench measurements lets put both an AB and D into the real world... a car trunk.

I prefer class D. I think the transients and dynamic capabilities are better in an equal power standpoint. Here's why... efficiency! a class D amplifier is going to sag the supply much less, the supply WILL sag, I don't care what you have under the hood, how thick of cable you are running, etc.... it's GOING to sag! This cannot turn into a regulated/un-regulated debate either, the regulation in those power supplies cannot "look ahead" and Will not till they get digital inputs or some serious DSP to delay the output and actually adjust for power supply demands "before" the output waveform. Like look-ahead limiting on pro audio processors. 

So we have a single kick with a nice sustain, or better yet (gasp) the infamous Roland 808 kick drone (for you hip hop fans) with an AB the initial attack will be just fine, the internal filtering/storage will account for this draw, but what happens when the caps are depleted for the sustain or drone? That's that "tongue-out blaaaaaw" you hear in street beaters.... the sound of a power supply frantically trying to catch up with a limited input voltage to the amplifier. The sound of money for me as I increase my Mouser order for new switching FETs for the poor sap. A class D amplifier will exhibit LESS of this issue, at WOT.

We are talking about running amps hard here, not loafing along. I challenge anyone to hear a difference in modern topologies in the LF domain under light operating conditions, But when you drop the hammer I feel that the difference can be heard (felt), not BECAUSE of the amplifier DESIGN but because of the outside operating conditions of 99.9% of the vehicle power supplies that WE will be running. Class D is better at getting the required power for the job from the battery to the voice coil, remember, it's an amplifier, that's it. 

This debate has gone around the pro audio circles for decades now, First with the most popular G/H designs that Bobby Carver made popular in the PM series, all the way up into the more modern Lab Gruppen, Powersoft, Peavey DPC, QSC Powerlights. Early on it was a pretty much traditional output section Class AB, G, H, we were pretty much cool with that, BUT what was discovered is that a traditional power supply (Iron and lytic) making an amplifier way close to 80 lb, sounded more substantial on the bottom end than a switcher supply. Granted the switcher was light and saved money in gas and labor. It also made our AC distro's happier. But for some reason the oldie, recharging beer can caps at 120 times a second, just seemed to do a better job at conveying authority On the bottom octave than a high speed switcher charging a bank of smaller caps thousands of times a second. You saw the switcher PS's on top boxes and sometimes lows, crest 8001's /9001's, Crown MA3600's and 5000's, and QSC EX's still prevailed as choice sub amps. We made a deal, things were still lighter.

Then along came class D output stages. Hmmmmm, with AB the low end was warmer under stress than class D , but you could get TREMENDOUS power on a whim out of class D, it just seemed to control the driver better... and it did with extensive feedback, at this time the power supply Field was evened out, the Crown K series used a traditional PS and a class D output stage, people liked them, then Gruppen and powersoft started the all PWM amps and they still sounded good. A revolution was born, Crest discontinued the 8001's and 9001's, times they were-a-changin!

Of course us road-tired whiners could not go without bitching, we did not like the top end of early class D designs. Under stress the output filtering would drift around from heat. Artifacts made the output sound "harsh" this was compounded with ultra low inductance coils that were just getting lower with technology. Again a preference was born, no class D's on mids and highs, but a PWM power supply was still acceptable there. But to prove us Nancy-whiners wrong.. technology! Component production quality is advancing, switching FETs got faster in the time it took me to write this and better filtering technologies were invented/tweaked. Now you still have whiners but the advantages of class D amps and PWM supplies FAR out-weigh the traditional workhorse design. These attributes are: Insane efficiency numbers, HUGE peak power capabilities, lower weight and smaller chassis saves transportation costs, happier crew, less copper in the distro's, less line sag all around.

And the most important thing that I have always said while embracing the technology that I will adapt in a few words for car audio.

There is no way you will walk into a venue (or a car) and go "hey they have switchers, I can hear it", it just ain't gonna happen. Yes there are different attributes under heavy loading and at the ragged edge, but there is no way in hell you will be able to tell without knowing the room (*car) like the back of your hand and having something to directly compare it to for a good period of time. After saying that and adhering to this theory there is no reason to NOT embrace modern amplifier technology no matter what it is.

Chad


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## kappa546 (Apr 11, 2005)

chad said:


> After saying that and adhering to this theory there is no reason to NOT embrace modern amplifier technology no matter what it is.
> 
> Chad


pfff what do you know, you have dial-up   ... i tease i tease. i'm back home from college and my mom has dialup too.... how lame.


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## durwood (Mar 7, 2007)

kappa546 said:


> pfff what do you know, you have dial-up   ... i tease i tease. i'm back home from college and my mom has dialup too.... how lame.


LOL.

You know I tried to embrace T-class twice. It failed me both times (as in the amps died for no reason). I do have to admit there are a few class D sub amps I liked, but too much $$ for me. I like to buy everything second hand though. I like where the new technology is taking us, i.e. smaller footprint amps and less strain on the elctrical system, but I'm still leary. I see everyone (JL,Alpine,Kenwood,Eclipse, Blaupunkt,etc) jumping onboard the fullrange classD train, but is a short trip or a long trip? That's what I want to know.


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## chad (Jun 30, 2005)

kappa546 said:


> pfff what do you know, you have dial-up   ... i tease i tease. i'm back home from college and my mom has dialup too.... how lame.


At this very second I am 3' away from the fiber and have gigabit coming in to the machine  

Dial up is at home. BUT I may have wireless soon, and possibly for free as I may be putting a repeater antenna up on the tower! I meet the criteria for backup power, tower height and topographical height. We need to toss an antenna up there and make sure there is no inter-mod from the other stuff hanging off of it.

That will make me MUCH happier!

Chad


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## Lightninghoof (Aug 6, 2006)

Bang and Olufsen's ICEPower Class D system (Alpine PDX) FTW!


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## MarkZ (Dec 5, 2005)

durwood said:


> LOL.
> 
> You know I tried to embrace T-class twice. It failed me both times (as in the amps died for no reason). I do have to admit there are a few class D sub amps I liked, but too much $$ for me. I like to buy everything second hand though. I like where the new technology is taking us, i.e. smaller footprint amps and less strain on the elctrical system, but I'm still leary. I see everyone (JL,Alpine,Kenwood,Eclipse, Blaupunkt,etc) jumping onboard the fullrange classD train, but is a short trip or a long trip? That's what I want to know.


In terms of reliability, a well-designed class D should outlive its class B counterpart. Why? Less heat (due in part to the efficiency state that the transistors are operating under) means lower max temps and less severe thermal cycles, and also because of an easier to predict adherence to the SOA curve for the output devices. But with many of the designers using smaller heatsinks or fewer output devices, it tends to counteract those inherent advantages. So, as always, it comes down to how much the manufacturer wants to get away with. If they built their class D amps with the same amount of balls they do with the class B, then it's no contest. But part of the appeal of class D is the small footprint, etc.


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## npdang (Jul 29, 2005)

Some people are comparing actual amps, and some people are comparing amp topologies and design. That makes for a very confusing discussion.


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## 300Z (Mar 20, 2005)

npdang said:


> Some people are comparing actual amps, and some people are comparing amp topologies and design. That makes for a very confusing discussion.


Now we are starting to get somewhere...


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## kyheng (Jan 31, 2007)

By topic on the thread is more on class vs class, I guess it should be topologies?


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## cvjoint (Mar 10, 2006)

chad said:


> There is no way you will walk into a venue (or a car) and go "hey they have switchers, I can hear it", it just ain't gonna happen. Yes there are different attributes under heavy loading and at the ragged edge, but there is no way in hell you will be able to tell without knowing the room (*car) like the back of your hand and having something to directly compare it to for a good period of time. After saying that and adhering to this theory there is no reason to NOT embrace modern amplifier technology no matter what it is.
> 
> Chad


However americans live in their cars more than the average folk and they get used to their car acoustics. The driver does not care whether thany can tell the difference in a different car when music plays for less than a cd lenght. What matters is that if you notice a difference in their car in between a class D and a class A/B where the later sounds better every time you will pick A/B over D anytime to save yourself the trouble.

MY understanding is that the more efficient designs manipulate power supplies to shut off partially or totally when not needed. What if the ear in fact can pick up this difference in design with music?


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## MarkZ (Dec 5, 2005)

cvjoint said:


> MY understanding is that the more efficient designs manipulate power supplies to shut off partially or totally when not needed. What if the ear in fact can pick up this difference in design with music?


You may be referring to a PWM supply, in which the duty cycle can become small under situations where little current is delivered (although never off -- it needs to stay on in order to energize the rails). That kind of strategy is also present in most class B car amps. Also keep in mind that the "on" pulses are happening at minimum 25000 times per second. So they're not exactly going off for any appreciable amount of time. 

Maybe you're referring to class G operation? A portion of the power supply shuts off in a sense I suppose. All it does is switch from the high voltage tap on the transformer to the low voltage tap(s). Some designs could potentially introduce measurable distortion byproducts from the actual switching, but recent designs supposedly utilize shottkey diodes to eliminate switching artifacts. Not sure how the few car audio manufacturers who do class G implement it. But regardless, class G is typically a lot closer to class B than it is to class D.


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## cvjoint (Mar 10, 2006)

MarkZ said:


> You may be referring to a PWM supply, in which the duty cycle can become small under situations where little current is delivered (although never off -- it needs to stay on in order to energize the rails). That kind of strategy is also present in most class B car amps. Also keep in mind that the "on" pulses are happening at minimum 25000 times per second. So they're not exactly going off for any appreciable amount of time. .


Well...how fast is fast enough? I'm thinking 25000/s is far faster than what the ear could pick up but what if in practice it isn't. 

I copied some stuff from wiki maybe I can find more sq. shaping amp. topology:

"The quantization of the output signal implies sampling like that done in A/D conversion, but such amplifiers' input and output signals are still analog."

In my experience going through a couple A/D conversions creates sort of a dull sound, maybe that's what some perceive as D and A/B difference.

"The output contains, in addition to the required amplified signal, unwanted spectral components (i.e. the pulse frequency and its harmonics) that must be removed by a passive filter. The filter is usually made with (theoretically) lossless components like inductors and capacitors in order to maintain efficiency."
I'm guessing this where the "shottkey diodes" come in right? Do all amplifiers have these?


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## boarder124 (Mar 16, 2006)

I have tried both also, and in my next ride i will have all class a/b. If i want to go with a lot of power, then i will throw in the class d amps, but otherwise i usually prefer a/b, i guess i am one who can "hear the difference".


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## thehatedguy (May 4, 2007)

I was thinking the amp needed to switch 3-5x faster than the highest frequency it was speced to play so that the ear would not pick up the switching speed.


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## thehatedguy (May 4, 2007)

Amps ahve diodes in the PS, but to remove the switching artifacts you would use an inductor most of the the time. Go over to ampguts.com and look a the boards of the large class d amps. You will see coils in the PS and coils near the ouputs. The coils near the outputs are what is filtering the digital noise- it is a crossover just like you would use on a speaker. And the coils on the outputs is why most class D amps have such poor damping factor.



cvjoint said:


> Well...how fast is fast enough? I'm thinking 25000/s is far faster than what the ear could pick up but what if in practice it isn't.
> 
> I copied some stuff from wiki maybe I can find more sq. shaping amp. topology:
> 
> ...


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## chad (Jun 30, 2005)

thehatedguy said:


> I was thinking the amp needed to switch 3-5x faster than the highest frequency it was speced to play so that the ear would not pick up the switching speed.


It's getting rough because some people are talking about switching (PWM) Power supplies and some are speaking of PWM output stages. A class D car amp will have both. Almost all car amps have a PWM supply to kick single ended 12V up to biploar rail voltage and bipolar low voltage for buffering, etc.

If a power supply had to switch at 3-5X then a traditional linear supply in nearly most home audio and older pro would not work.... they recharge at 120Hz.

But for PWM final stages the higher the better within the device specs. Too many designers pushed these specs once and gave class D a bad rap IMHO. Today's results work.


----------



## thehatedguy (May 4, 2007)

I was talking about the amplifier chip itself...not the PS. Those chips will oscillate, and you need that a few times outside of the highest freq the amp is designed to play.

Found this on DIYAudio:

http://www.irf.com/product-info/audio/classdtutorial.pdf


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## chad (Jun 30, 2005)

thehatedguy said:


> I was talking about the amplifier chip itself...not the PS. Those chips will oscillate, and you need that a few times outside of the highest freq the amp is designed to play.
> 
> Found this on DIYAudio:
> 
> http://www.irf.com/product-info/audio/classdtutorial.pdf


Absolutely, was just making sure everyone is on the same page.


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## durwood (Mar 7, 2007)

Well according to that sheet, switching frequency is ~400Khz for the output devices. Parasitic effects have to be accounted for at that high of a frequency. Back in the days they must have been ignoring such factors or were operating such devices at their extreme tolerances. Technology improves overtime makes me want to give class D another chance.


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## MarkZ (Dec 5, 2005)

cvjoint said:


> Well...how fast is fast enough? I'm thinking 25000/s is far faster than what the ear could pick up but what if in practice it isn't.


It's not really a matter of speed. The switching frequency is pretty much set. It's the duty cycle that changes with load in those amps. But yes 25kHz (or, usually higher, like 30kHz or 35kHz -- sometimes much higher than that) is ultrasonic, and it's filtered. You won't hear it. That's why it's chosen to be so high. Just to reiterate, that's present in both classes. It's just a PWM supply.

Like chad mentioned, don't confuse the power supply with the amplifier proper. You mentioned the "off" state of the power supply. But that doesn't really exist unless you're talking about the fact that the FETs that drive the transformer are switching on and off at an incredibly high rate. 

Class D amplification, however, operates on a pseudo-sampling basis which has a "sampling rate" that's much higher. The input signal is transformed into a series of pulses at a set fundamental frequency but with a duty cycle that varies according to the amplitude of the input signal. The resulting signal is amplified by transistors that are switching on and off (their most efficient state), and then lowpass filtered to remove that switching frequency.



> I copied some stuff from wiki maybe I can find more sq. shaping amp. topology:
> 
> "The quantization of the output signal implies sampling like that done in A/D conversion, but such amplifiers' input and output signals are still analog."
> 
> ...


Many class B amps have output inductors and capacitors too. Actually, most good ones have some sort of zobel compensation at the output, but you don't see it terribly often in car audio IME.

The wiki you're referring to doesn't really say what the source of the "dullness" could be. If it's the switching frequency and harmonics, then it would manifest itself as noise. I guess it could be due to poor freq response, but that's easy enough to show in a freq resp test. But I really haven't seen that as the case.



> I'm guessing this where the "shottkey diodes" come in right? Do all amplifiers have these?


No, that's for the class G amplifier.


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## FoxPro5 (Feb 14, 2006)

Mat Dope said:


> i searched and didnt find much about this.
> 
> just wonder for a sub amp is there actually a difference that you can hear and that affects SQ and mechanically is their actually a difference. i know in terms of efficancy but what else.
> 
> ...


This might sound rude, but one cannot hear anything unless they make an honest point NOT to try to hear any differences. The very act of trying to hear pretty much ruins it. In scientific analysis, this is called the Avis Effect. In other words, when people say "I'm trying to hear" they are speaking in pure nonsensical terms. One cannot try to hear, just like one cannot go sight seeing. It's an arguement in semantics, yes...but lets just get down to the brass tacks here for a second.

I really don't mean go get into a deep philosphical discussion, but I think this is a valid point in these discussions about what people THINK they can hear and what they actually ARE hearing. I dunno, it seems it's rarely mentioned.

That said, if I changed your amps from A/B to D in the middle of the night, I'd give you a 100% chance you would never know. 

Great info on amps in this tread though.


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## Abmolech (Nov 2, 2006)

> That said, if I changed your amps from A/B to D in the middle of the night, I'd give you a 100% chance you would never know.


Yeah but my rottweiler in my car wouldn't need feeding for a day or two.


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## cvjoint (Mar 10, 2006)

B-Squad said:


> That said, if I changed your amps from A/B to D in the middle of the night, I'd give you a 100% chance you would never know.
> 
> Great info on amps in this tread though.


I beg to differ. I don't understand you guys, why would I claim A/B sounds better especially when I don't have the technical expertise to back it up? I don't win anything by putting my experience out there.

I believe in technology and I hope one day class D will sound just as good, I have everything to gain from it.


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## 89grand (Nov 23, 2006)

cvjoint said:


> I beg to differ. I don't understand you guys, why would I claim A/B sounds better especially when I don't have the technical expertise to back it up? I don't win anything by putting my experience out there.
> 
> I believe in technology and I hope one day class D will sound just as good, I have everything to gain from it.


It's not really that hard to see why you believe that. Obviously you've heard an A/B that for some reason sounded better than a class D, but I have a real strong feeling there were actually other things behind it other than the topology of the amp.

More power, totally different setups, a good A/B vs a real ****ty class D etc.


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## cvjoint (Mar 10, 2006)

89grand said:


> It's not really that hard to see why you believe that. Obviously you've heard an A/B that for some reason sounded better than a class D, but I have a real strong feeling there were actually other things behind it other than the topology of the amp.
> 
> More power, totally different setups, a good A/B vs a real ****ty class D etc.


The polk 300.2, arc 2500xxk > polk 500.1, orion 2500d, Soundstream 6500d

I can tell the difference in between the A/B and the Ds but not between the A/B. The Polk and the Arc are actually the only two I can't recognize on any type of speaker they play on.


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## chad (Jun 30, 2005)

Abmolech said:


> Yeah but my rottweiler in my car wouldn't need feeding for a day or two.


Good one  

My rottie will not protect the car.... The truck is a different story..... DOGS LOVE TRUCKS!


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## t3sn4f2 (Jan 3, 2007)

cvjoint said:


> I beg to differ. I don't understand you guys, why would I claim A/B sounds better especially when I don't have the technical expertise to back it up? I don't win anything by putting my experience out there.
> 
> I believe in technology and I hope one day class D will sound just as good, I have everything to gain from it.


We aren't saying you can't hear a differance, we are saying the the factors that make you hear a differance are not due to amp topologies. If you are lucky to have enough current, heat management, money, vehicle weight capacity, space and I don't know what else for an A/B amp then go for it, but if not then you are only selling yourself short.


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## cvjoint (Mar 10, 2006)

B-Squad said:


> This might sound rude, but one cannot hear anything unless they make an honest point NOT to try to hear any differences. The very act of trying to hear pretty much ruins it.


That would be to say the Revelator line sounds better than the Xplod line only because people are trying to hear the difference. I'm sure there is a hint of placebo effect in anything but not enough to make it the central variable. On the contrary, trying to listen carefully works better than casually hearing music in the background. I bet everyone here at some point closed their eyes behind their steering wheel trying to grasp improvements in quality of sound.  




t3sn4f2 said:


> We aren't saying you can't hear a differance, we are saying the the factors that make you hear a differance are not due to amp topologies. If you are lucky to have enough current, heat management, money, vehicle weight capacity, space and I don't know what else for an A/B amp then go for it, but if not then you are only selling yourself short.


Than explain to me what the vectors would make me choose the polk a/b amps vs. the polk monoblock, or for that matter the before mentioned 2500xxk over 1500d mono version? If there is anything different between the above it would be the class difference.


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## t3sn4f2 (Jan 3, 2007)

cvjoint said:


> That would be to say the Revelator line sounds better than the Xplod line only because people are trying to hear the difference. I'm sure there is a hint of placebo effect in anything but not enough to make it the central variable. On the contrary, trying to listen carefully works better than casually hearing music in the background. I bet everyone here at some point closed their eyes behind their steering wheel trying to grasp improvements in quality of sound.
> 
> 
> 
> *Than explain to me what the vectors would make me choose the polk a/b amps vs. the polk monoblock, or for that matter the before mentioned 2500xxk over 1500d mono version? If there is anything different between the above it would be the class difference.*


So what are saying is that class D amps have a characteristic sonic signature with regards to measurable parameters such as frequency response, distortion, noise, ect., that makes them distinguishable from class A/Bs?


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## cvjoint (Mar 10, 2006)

t3sn4f2 said:


> So what are saying is that class D amps have a characteristic sonic signature with regards to measurable parameters such as frequency response, distortion, noise, ect., that makes them distinguishable from class A/Bs?


It's deffinetly not noise...it's more like a sterile sound the D puts out, combined with a slower attack time on fast bass tracks. I don't know where to place the characteristics from above in the common list of amp differences that you listed but the sense of depth and low end grunt could be attributable to a more extended frequency response. Someone mentioned here already that Ds might be band limited to provide better efficiency. It makes sense because my polk are filtered at 15hz subsonic and tend to sound a bit softer than other amps. It would also explain why some people that use high subsonic filters 20hz and above would not hear much difference between D and A/B, the differences lying mainly for free air, sealed application where a subsonic is generally not used.

Chad also mentioned that A/Bs tend to sound warmer on the lower notes if I remember. Warm vs. sterile.


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## t3sn4f2 (Jan 3, 2007)

cvjoint said:


> It's deffinetly not noise...it's more like a sterile sound the D puts out, combined with a slower attack time on fast bass tracks. I don't know where to place the characteristics from above in the common list of amp differences that you listed but the sense of depth and low end grunt could be attributable to a more extended frequency response. Someone mentioned here already that Ds might be band limited to provide better efficiency. It makes sense because my polk are filtered at 15hz subsonic and tend to sound a bit softer than other amps. It would also explain why some people that use high subsonic filters 20hz and above would not hear much difference between D and A/B, the differences lying mainly for free air, sealed application where a subsonic is generally not used.
> 
> Chad also mentioned that A/Bs tend to sound warmer on the lower notes if I remember. Warm vs. sterile.


Would you then be open to doing a _proper_ blind comparison test to see if its not all in your head and so that you can benefit from all the advantages of class D?


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## cvjoint (Mar 10, 2006)

t3sn4f2 said:


> Would you then be open to doing a _proper_ blind comparison test to see if its not all in your head and so that you can benefit from all the advantages of class D?


I consider direct swapps in my car as being more than proper comparisons. I would be willing to make an hour drive anywhere in So. Cal. for a comparison, especially if there are some amps that I've used before, I'm allowed to listen for more than a few seconds and I get to pick the music


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## thehatedguy (May 4, 2007)

When I changed from class D on the subs to a/b, everyone who heard the car (not knowing that I had changed anything) commented on how nice the bass sounded now (after the change). I kept levels the same and had similar power to the speakers. Amps were 2 JL 500/1s and a US Amps 1000X.

I don't know what the change was attributed to, but it was there after the car was retuned.


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## DonutHands (Jan 27, 2006)

if anything, wouldent a/b be slower on "fast bass tracks" as someone put it, than a class D. im not even going to comment on warm sounding amps, much less warm sounding bass amps.


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## cvjoint (Mar 10, 2006)

internecine said:


> if anything, wouldent a/b be slower on "fast bass tracks" as someone put it, than a class D. im not even going to comment on warm sounding amps, much less warm sounding bass amps.


I think that was the case if there isn't enough juice too feed the a/b or it's just near its limits. To me it just feels like the D is an on/off type of deal that looses some musicality in comparison to the A/B that feels much more alert to what you are feeding it.


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## thehatedguy (May 4, 2007)

I never said anything about warm sounding amps.

I do have a SET tube amp for the car...but it isn't warm sounding either.


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## MarkZ (Dec 5, 2005)

internecine said:


> if anything, wouldent a/b be slower on "fast bass tracks" as someone put it, than a class D. im not even going to comment on warm sounding amps, much less warm sounding bass amps.


Hehe, this is getting out of hand. So what's "slower" mean? Are you referring to the difficulty in reproducing fast kick drums (eg. when Lars gets his double bass drum going  )? Or are you talking about the initial impact you get on a bass transient? In either case, I've found it's mostly an effect dominated by the midbass drivers (and the interaction between sub and midbass). IMO, too much blame is placed on the sub when the midbass is to blame.



cvjoint said:


> To me it just feels like the D is an on/off type of deal that looses some musicality in comparison to the A/B that feels much more alert to what you are feeding it.


What do you mean by an "on/off type of deal"? I've never really heard that description before.


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## FoxPro5 (Feb 14, 2006)

cvjoint said:


> I beg to differ. I don't understand you guys, why would I claim A/B sounds better especially when I don't have the technical expertise to back it up? I don't win anything by putting my experience out there.
> 
> I believe in technology and I hope one day class D will sound just as good, I have everything to gain from it.


Ok how about this one then. When's the last time you heard a really great sounding system and said "Wow those amps sound fantastic!!" My point is that amps shouldn't have sound quality. In my opinion, if they did, something is wrong. Quantity, on the other hand......

I think it's great you can tell a difference, really. I'm not doubting your experience or anything. But the mind can be easliy persuaded when the limbic system starts making car audio purchases.


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## thehatedguy (May 4, 2007)

Key word that qualified your statement...the SHOULDN'T affect or effect the sound. But in the real world they (amps) do this.


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## FoxPro5 (Feb 14, 2006)

thehatedguy said:


> But in the real world they (amps) do this.


In your experience then, which factors contribute to the phenomenon? How do you know by listening indirectly to the amp? Because don't we really listen to the amp via the speakers?


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## MarkZ (Dec 5, 2005)

thehatedguy said:


> Key word that qualified your statement...the SHOULDN'T affect or effect the sound. But in the real world they (amps) do this.


That is, of course, the issue here once all the dust settles. Or, more accurately, how do you have to operate an amplifier to get it to sound different from another one? How much clipping, how much do you starve the electrical system, etc before you can hear the difference. It sounds to me like cvjoint's experience has led him to believe that these differences are intrinsic to the amplifier topologies, independent of the actual conditions of operation. In other words, "class D sounds like this and class B sounds like that..." I haven't come across the same finding, and I'm having trouble figuring out what could account for it _unless_ he was operating these amps beyond their limitations or under different conditions.


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## thehatedguy (May 4, 2007)

I don't think any one thing is inherent to the topology...the key is the designer's goals. Take Nelson Pass for example. His amps are all class A single ended transistor amps, but he can design one that has higher odd order distortion like the F1 to make it sound clean and analytical, but the F3 has higher 2nd order distortion that makes it more "pleasant" to most people's ears. Different design objectives for different groups of people.

When I was looking at an amp kit to build for my home horns, I wanted a tube amp for that classic "glassy tube midrange"...or so I thought. The single ended guys basically said "why would you want an amp to do that? That is high distortion causing that effect." And they could design an improper working amp for me if they wanted to...but would advise against it. SETs don't have that midrange sag and sound b/c there is no crossover distortion going on. And like Nelson, you can tailor the sound for the design goals.

But IMO all of this is a moot point if you are talking about listening to amps on 85 dB efficient speakers...it is going to take a lot of work compared to a high efficiency speaker to get the same amount of output...thus you wouldn't be in the realm of hearing differences in amps. Now if you had a speaker that was 105-108 dB efficient (or more), I would be more inclined to start talking about small differences making audible sonic effects...just because you are now listening to fractions of a watt versus decades of watts.


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## thehatedguy (May 4, 2007)

In a/b designs on high efficiency speakers you could have crossover distortion. Then there could be FR changes with inductance, high impedance output devices like transformers. Or you could have power supplies that have no room for dynamic and transient reserves...PS with too much rail sag.

But I'm no EE or amp designer, so I can't give you a magic recipe as to what ingredients gets a certain sound. I think if someone really could do that, then you would have really successful amp emulators for the home market...



B-Squad said:


> In your experience then, which factors contribute to the phenomenon? How do you know by listening indirectly to the amp? Because don't we really listen to the amp via the speakers?


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## MarkZ (Dec 5, 2005)

thehatedguy said:


> I don't think any one thing is inherent to the topology...the key is the designer's goals. Take Nelson Pass for example. His amps are all class A single ended transistor amps, but he can design one that has higher odd order distortion like the F1 to make it sound clean and analytical, but the F3 has higher 2nd order distortion that makes it more "pleasant" to most people's ears. Different design objectives for different groups of people.
> 
> When I was looking at an amp kit to build for my home horns, I wanted a tube amp for that classic "glassy tube midrange"...or so I thought. The single ended guys basically said "why would you want an amp to do that? That is high distortion causing that effect." And they could design an improper working amp for me if they wanted to...but would advise against it. SETs don't have that midrange sag and sound b/c there is no crossover distortion going on. And like Nelson, you can tailor the sound for the design goals.
> 
> But IMO all of this is a moot point if you are talking about listening to amps on 85 dB efficient speakers...it is going to take a lot of work compared to a high efficiency speaker to get the same amount of output...thus you wouldn't be in the realm of hearing differences in amps. Now if you had a speaker that was 105-108 dB efficient (or more), I would be more inclined to start talking about small differences making audible sonic effects...just because you are now listening to fractions of a watt versus decades of watts.


That's true, you can design an amplifier to have certain characteristics that would be audible and might have a different sound to them from another one. Or you could design an amplifier to produce virtually no distortion -- the so-called "blameless" amplifier. Most car audio amps I've seen tend to fall somewhere in the middle. I've yet to encounter one that really takes every possible approach to eliminating distortion and flattening FR while remaining stable, but all of them I've tested or repaired do a pretty good job of it. You've always got the occasional amp that doesn't have defeatable tone controls and stuff like that, so you're always left with some residual bumps, but I wouldn't count that . But, like I mentioned, I don't design or do repairs or mods for a living, so my sample size is admittedly small.

Anyway, I don't generally find crossover distortion to be much of an issue in modern amplifiers, almost all of which employ massive amounts of negative feedback. So most of what you describe (eg. rail sag and reserves) are properties that become issues only when you're driving the amp fully. The power supply otherwise has very little bearing on the output of the amp (assuming the PSRR is high enough, which I think is a fair assumption with modern day amplifiers). That is, you're either clipping or you're not. 

Granted, driving an amp to its limits is very much a real world issue, so it shouldn't be glossed over as much as what I'm doing . But I think it serves to illustrate the point that if you're worried about how the class B amp behaves near clipping in comparison to the class D amp, just double the power of your class D amp and the issue becomes moot.  There aren't inherent flaws with really any of the designs out there that I'm aware of (in the car, at least) that higher vrails can't solve. [again, aside from noise, which is another issue IMO]


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## cvjoint (Mar 10, 2006)

MarkZ said:


> What do you mean by an "on/off type of deal"? I've never really heard that description before.


 Hard to say  hmmm...A/B is smooth, real-time and picks up the smallest subtle bass tones, the D would be too composed it's either working or not. For example...drum and bass usually has this continuous bass line from a little past the begining of the song till the end. While the bass note is continously on, varying in frequency or not the D will sound terribly close to an A/B almost no difference. It's the genres with fast paced bass like trance that make the most difference. 



B-Squad said:


> Ok how about this one then. When's the last time you heard a really great sounding system and said "Wow those amps sound fantastic!!" My point is that amps shouldn't have sound quality. In my opinion, if they did, something is wrong. Quantity, on the other hand......


I remember testing the Jl Slash series, and the Kicker Sx and noting a big difference in sound vs. the polks.



B-Squad said:


> How do you know by listening indirectly to the amp? Because don't we really listen to the amp via the speakers?


You don't necessarily have to listen directly to the amp. Ceteris Paribus - hold everything else constant. Switch inbetween two amps on the same speaker setup.


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## FoxPro5 (Feb 14, 2006)

cvjoint said:


> Hard to say  hmmm...A/B is smooth, real-time and picks up the smallest subtle bass tones, the D would be too composed it's either working or not. For example...drum and bass usually has this continuous bass line from a little past the begining of the song till the end. While the bass note is continously on, varying in frequency or not the D will sound terribly close to an A/B almost no difference. It's the genres with fast paced bass like trance that make the most difference.
> 
> 
> 
> ...



No, I meant like hearing a system for the first time!  NOT an A/B test on your own equipment. Those differences are pretty easily identifyable with just a quick swap and nothing else. However, as mentioned many times before, it's not the topology that can be attributed as what's making the difference.


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## MarkZ (Dec 5, 2005)

cvjoint said:


> Hard to say  hmmm...A/B is smooth, real-time and picks up the smallest subtle bass tones, the D would be too composed it's either working or not.


Dude, I think it's all in your head.  You were probably influenced by that idea you had that the power supplies in class D amps were shutting off, or whatever it was.


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## cvjoint (Mar 10, 2006)

B-Squad said:


> No, I meant like hearing a system for the first time!  NOT an A/B test on your own equipment. Those differences are pretty easily identifyable with just a quick swap and nothing else. However, as mentioned many times before, it's not the topology that can be attributed as what's making the difference.


You mean notice that 2% sound difference that the amp makes...neah, I don't have superpowers. It's just that the most tiny difference for the worse will get you to swap back to an old amp because you are so familiar with your car acoustics.

I got to thinking about proper amp testing settings and overall I do have two major issues unresolved: 

I never tested amps with xovers off

I'm runnning the same exact amp for the whole setup, it MAY just be that no other class D design sounded as good because it just wasn't matched with the other amps. In other words what if the speaker amps were all class D and I would try to run a class a/b sub amp...it may not sound as good simply due to general amp fingerprint. Just a possibility.


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## chad (Jun 30, 2005)

cvjoint said:


> Chad also mentioned that A/Bs tend to sound warmer on the lower notes if I remember. Warm vs. sterile.


I mentioned that in pro audio people preferred linear power supplies on AB amps over PWM power supplies because it SEEMED the linears delivered the goods better/longer.

In a car it's no contest because there are no linear power supplies.

On the ragged edge I think the efficiency of PWM final sections prevail in terms of cone control and energy transfer. I like to talk about what amps do on the ragged edge, because I believe that in normal operating condtions they should all perform the same.

Chad


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## FoxPro5 (Feb 14, 2006)

cvjoint said:


> You mean notice that 2% sound difference that the amp makes...neah, I don't have superpowers.


No, I meant the 0% it makes.  Nevermind acutally, you aren't getting what I was saying. Keep your A/B's and rock them out.


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## 89grand (Nov 23, 2006)

I'm glad I don't hear a difference. My class D works just fine...and draws a lot less current while doing it.

Class D FTMFW...w00t!


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## cvjoint (Mar 10, 2006)

My bad Chad most of the stuff you write just goes over my head.

Well I guess I'm done arguing, these debates never solve anything do they?


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## t3sn4f2 (Jan 3, 2007)

cvjoint said:


> My bad Chad most of the stuff you write just goes over my head.
> 
> Well I guess I'm done arguing, these debates never solve anything do they?


delete


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## 60ndown (Feb 8, 2007)

i ran a class d "orion 2500d" (2500wrms) for over a year in my van great amp, changed to a 'tru hammer' class a/b maybe 1200wrms, it sounds better. and in EXACTLY the ways cvjoint is talkin bout.the speed, the dynamics, the weight, the depth, the musicality....ALL BETTER. maybe the orion amp is not a good class d?


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## raamaudio (May 4, 2005)

None of us have the same finger prints do we?

Maybe we have differences in the way we hear things? Kind of makes sense when you look at it this way, seems like a perfectly logical explanation. 

For those looking from a scientific viewpoint is it possible we have not "discovered" all their is yet to discover? I would hope so.

If we can turn off our emotions during times like this (not easy to do for such passionate people) and look at this from a more open minded perspective maybe we can agree to disagree and accept that just maybe each of us hears things a bit differently than others do. Instead of trying to win a winless argument why argue at all?

 Rick


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## durwood (Mar 7, 2007)

raamaudio said:


> For those looking from a scientific viewpoint is it possible we have not "discovered" all their is yet to discover? I would hope so.


I was just thinking the same thing the other day. I agree that there are "other" factors we might not have discovered yet.


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## t3sn4f2 (Jan 3, 2007)

Where are all the $10,000 dollar amp challenge winners?


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## durwood (Mar 7, 2007)

t3sn4f2 said:


> Where are all the $10,000 dollar amp challenge winners?


living on the same island with Elvis, Kurt Cobane, and friends.


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## 89grand (Nov 23, 2006)

t3sn4f2 said:


> Where are all the $10,000 dollar amp challenge winners?


I don't know, but there should be plenty of them considering the amount of people that can easily tell the difference between amps.


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## 300Z (Mar 20, 2005)

t3sn4f2 said:


> Where are all the $10,000 dollar amp challenge winners?


Please go read AND understand what that challenge really means.


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## t3sn4f2 (Jan 3, 2007)

300Z said:


> Please go read AND understand what that challenge really means.


AND please go back and read between the lines and get the essence of what the challenge is suppose to make people realize. The differences you hear at the very least are not due to attributes of an amp class and could be had with careful planning an open mind and much less wasted money.


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## durwood (Mar 7, 2007)

Why bring up the 10K amp challenge again? Over and over. A vicicous cycle.

There are certain criteria an amp must meet to even be used in the challenge, and you will not find that in cheaper branded amps straight out of the box. 

You know not everyone's ears are shaped the same, so is it possible that a person's ear shape can alter the way they hear how something sounds.

Also keep in mind, every amp produced has a prupose, look at how companies have varying levels of amps. Tru technology had several different amp style available at one time becuase everyone has a personal preference and certain things they need out of an amp.


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## t3sn4f2 (Jan 3, 2007)

durwood said:


> Why bring up the 10K amp challenge again? Over and over. A vicicous cycle.
> 
> *There are certain criteria an amp must meet to even be used in the challenge, and you will not find that in cheaper branded amps straight out of the box.
> *
> ...


Thats looking a little too deep into it, my point is keeping it simply to 2 amps with published honest specs that are close enough to each other and yet are thousands of $ apart in price. What are you paying for that you can hear? If you want a shinny heavy heatsink, fine that great. If you want an amp that will last you 30 years instead of 20 year fine too. But saying that you can hear a differance in a situation where all the factors that influence how you hear are not controlled is worng.


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## t3sn4f2 (Jan 3, 2007)

Edited the last piece there, said it wrong.


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## durwood (Mar 7, 2007)

I'll agree as the price gap difference between amps increases the value to better sound ratio goes down. there is a happy medium in there somewhere. It's pretty much where it doesn't hurt your wallet and you are happy with how it sounds.  Added disclaimer: Money also does not equal better either. 

Half of the factors in the amp challenge are product related and a consumer cannot alter staright out of the box.

The other half of the factors are install related or dependent on other outside forces, some of which can be corrected by install and some can't becuase it's a part of the more realistic enviroment they are being used in.


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## Lanson (Jan 9, 2007)

This is why I like my ICEpower Pioneer amp. Its like class D, but not quite. B&O (Bang and Olufsen) figured it out a while ago, and I think they got it right.

However,

I like my hybrid tube amps more.


<dons fireproof clothing and ducks>


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## chad (Jun 30, 2005)

fourthmeal said:


> I like my hybrid tube amps more.




Hybrid as in glass pre and sand output or sand pre and glass output?


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## phatredpt (Feb 22, 2006)

I am just throwing this out for comment..
Is it possible that it is just easier design-wise (and more economical from a production standpoint) to produce a "good" sounding A/B than it is to produce a "good" sounding Class D?
Perhaps that is why folks have "heard" a difference?

I was considering one of Eclipse's new class D sub amps and 2 things kept me from it...if you look closely you will find that they do use Icepower on most of the class D amps... but NOT the mono ones.. I assume the theory that on sub duty you wouldn't hear the difference so why pay the licensing fees.
The other was that when I went to audition it...the salesman was busy so one of the installers helped me...he admitted he did not know all the features of the different models.. but did offer up the info that in his experience the Eclipse mono did not SOUND as good as one of the lower price MTX A/B amps with lower power ratings bridged.
Trust me he was not highly educated nor did he even know the difference between amp classes.. he just shared what he had seen...and heard after being installed.

I am not taking sides at all...just wondering if this might be an explanation?


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## phatredpt (Feb 22, 2006)

chad said:


> Hybrid as in glass pre and sand output or sand pre and glass output?


They are the Planet Audio amps..glass in, silicone out I believe...
Adding some harmonics up front...pleasant harmonics


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## chad (Jun 30, 2005)

phatredpt said:


> They are the Planet Audio amps..glass in, silicone out I believe...
> Adding some harmonics up front...pleasant harmonics


If the tube is run in it's operating range.. and most are run lower than optimum due to the difficulty to get enough plate voltage, the glass preamp stage will be VERY linear with little to no harmonics. The tube has to be run pretty hard to get the desireable effect of the tube. I actually prefer the sound of discreet SS preamps to an underdriven tube. But you will have to pry my lower powered tube amps out of my cold lifeless hands. Cuz I like the way they sound balls out.

What's the plate voltage on the planet audio stuff?

Chad


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## chad (Jun 30, 2005)

phatredpt said:


> I am just throwing this out for comment..
> Is it possible that it is just easier design-wise (and more economical from a production standpoint) to produce a "good" sounding A/B than it is to produce a "good" sounding Class D?
> Perhaps that is why folks have "heard" a difference?
> 
> I was considering one of Eclipse's new class D sub amps and 2 things kept me from it...if you look closely you will find that they do use Icepower on most of the class D amps... but NOT the mono ones.. I assume the theory that on sub duty you wouldn't hear the difference so why pay the licensing fees.


Is the Icepower full range and the other sub only? That could be the difference.


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## DS-21 (Apr 16, 2005)

phatredpt said:


> I am just throwing this out for comment..
> Is it possible that it is just easier design-wise (and more economical from a production standpoint) to produce a "good" sounding A/B than it is to produce a "good" sounding Class D?
> Perhaps that is why folks have "heard" a difference?


Actually, as Chad alluded to, the difference (inasmuch as one exists, and I'm hardly convinced of that) probably has something to do with differences in filtering. 

For example, if you run a 100Hz, 12dB/oct crossover, and the amp has a brick wall filter at 200Hz, that certainly can sound different from an amp lowpassed at 100Hz, 12 dB/octave and flat response out to >400Hz.


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## MarkZ (Dec 5, 2005)

raamaudio said:


> None of us have the same finger prints do we?
> 
> Maybe we have differences in the way we hear things? Kind of makes sense when you look at it this way, seems like a perfectly logical explanation.


It's possible, but it's fairly well documented that the human capability of hearing stuff is fairly consistent. You'll get all kinds of individual variation, but it won't vary so wildly that you have superhuman-like sound detectors walking among us. We lack the machinery to be able to go to such extremes.



> For those looking from a scientific viewpoint is it possible we have not "discovered" all their is yet to discover? I would hope so.


Frankly, no. You can completely account for a signal with electrical measurements. It's highly unlikely that there are other undiscovered forces at play here aside from electrical.



> If we can turn off our emotions during times like this (not easy to do for such passionate people) and look at this from a more open minded perspective maybe we can agree to disagree and accept that just maybe each of us hears things a bit differently than others do. Instead of trying to win a winless argument why argue at all?


Well, it is a winnable argument. Just perform the test. Kinda hard to do over the internet though.


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## cvjoint (Mar 10, 2006)

t3sn4f2 said:


> delete


At least I tried to tell people what it was that I'm hearing as well as pointing out some of the flaws in my testing procedure.

If you have something so enlightening to say than why don't you bring it out? Anybody can bring the $10,000 challenge in the discussion and by now whether we want to or not we all know what the findings and significance.

If you were to test two nearly identical amps from the same company the only difference being class and found the A/B to sound better wouldn't you ditch the class D?


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## MarkZ (Dec 5, 2005)

cvjoint said:


> If you were to test two nearly identical amps from the same company the only difference being class and found the A/B to sound better wouldn't you ditch the class D?


How do you know that just because the two amps are from the same company that the only difference is class?


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## cvjoint (Mar 10, 2006)

MarkZ said:


> How do you know that just because the two amps are from the same company that the only difference is class?


If anything the class D should be a better performer...it has more power on tap and drains the electrical system much less.

Every manufacturer given electrical spec is the same from the 24db subsonic filter at 15hz, s/n, MDH ( some headroom improving tricks) etc.

The only apparent difference would be the one ds-21 pointed out that the D only goes up to 200hz as opposed to 45khz for the A/B, however the improvement in the later is in low end punch. I don't see why Polk would bump 20-40 hz fequecies on the 2 channel amp, it would most likely be on the D.


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## t3sn4f2 (Jan 3, 2007)

cvjoint said:


> At least I tried to tell people what it was that I'm hearing as well as pointing out some of the flaws in my testing procedure.
> 
> If you have something so enlightening to say than why don't you bring it out? Anybody can bring the $10,000 challenge in the discussion and by now whether we want to or not we all know what the findings and significance.
> 
> *If you were to test two nearly identical amps from the same company the only difference being class and found the A/B to sound better wouldn't you ditch the class D?*


If the test was conducted properly and the amps being compared were measured and came back the same as published specs then I would take the class D because I would then know its all in my mind and a few hours later I would be as happy as I would have been with the class A/B but with I twice the availiable current for other upgrade, more money in my pocket, less heatsink and heat for easier and longer lasting installs, ect., ect.


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## MarkZ (Dec 5, 2005)

cvjoint said:


> If anything the class D should be a better performer...it has more power on tap and drains the electrical system much less.
> 
> Every manufacturer given electrical spec is the same from the 24db subsonic filter at 15hz, s/n, MDH ( some headroom improving tricks) etc.


Spec sheets should not be confused with real testing. Spec sheets are notorious for not being worth the paper they're printed on.

Anyway, I don't think there's any guarantee that the two amps are going to be the same. In fact, it's the norm for the same manufacturer to use smaller heatsinks, fewer output devices, and sometimes a less bulky power supply in their class D versions of amps. That's not a drawback inherent to class D topology. That's called saving a buck.


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## 300Z (Mar 20, 2005)

To amps of different topology's from the same line, same manufacture does not mean they related at all. They may share the same chassis but the differences could end there. Different topology --> different amp altogether most of the time. Like everything else it's all about compromises and different approaches are used to build different amps.


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## cvjoint (Mar 10, 2006)

Things don't add up though. Why would the manufacturer cut corners so much on the D? Both amps are sold for the same price yet the D uses a smaller heatsink and it is probably altoghether cheaper to manufacture. If they were to push the profit margin it would be on the A/B cousin where marginal profit is smaller. I know manufacturer sheets are not 100% accurate and unbiased but within their own lineup and without a reason I don't see how the A/B would be grossly underrated.

The class D is bench tested to do at least 50w more than the class A/B and polk tends to give accurate specs as third party tests replicate the data sheet. I doubt polk would go to great lenghts to manufacture the two amps as completely different animals, and if biased it would be in favor of the D. It is their one and only sub amp whereas the 300.2 is most likely the one amp with least sales in the lineup.

One note...if the D is limited at 200hz isn't that because inherently this class would have issues with higher frequency reproduction? Would it be wrong to say a narrow frequency band is a characteristic of class D?


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## cvjoint (Mar 10, 2006)

t3sn4f2 said:


> If the test was conducted properly and the amps being compared were measured and came back the same as published specs then I would take the class D because I would then know its all in my mind and a few hours later I would be as happy as I would have been with the class A/B but with I twice the availiable current for other upgrade, more money in my pocket, less heatsink and heat for easier and longer lasting installs, ect., ect.


How do we know for sure you are not supporting class D because it is easier on your pocket? If you can't stop for a second and try to believe that I might actually hear a difference and it is not all in my head, than why shouldn't I believe that the lack of difference is all in your head for the greater purpose of saving a buck and not worrying about a saging electrical system?

How many nonbelievers in amp soundprint actually took the 10k challenge or conducted a fair and proper test to make sure the differences aren't really there?


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## 89grand (Nov 23, 2006)

Class D amps ARE NOT limited to 200hz. I don't even think DS-21 said they where either, he just used a hypothetical number, I think. For instance, my JBL GTO 600.1 is limited to 320hz according to the specs. Way beyond what any reasonable person would use a mono sub amp for.


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## ca90ss (Jul 2, 2005)

cvjoint said:


> How many nonbelievers in amp soundprint actually took the 10k challenge or conducted a fair and proper test to make sure the differences aren't really there?











Class A/B, D and T

When level matched with the internal crossovers and bass boost defeated I can't tell a difference between any of them when playing sub frequencies.


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## 300Z (Mar 20, 2005)

cvjoint said:


> How many nonbelievers in amp soundprint actually took the 10k challenge or conducted a fair and proper test to make sure the differences aren't really there?


Class D is not a band limited topology, the reason most car audio D class amps are is due to cost, a proper full range class D amp is both expensive and more difficult to build/design.

As for the challenge, those who keep making comparisons between the challenge and real world applications don't understand the challenge. In the real world different amps do measure different thus making them "sound" different IF the variances are large enough to be heard and this could be with any amp topology. You just need to know what causes those differences and take it out of the equation to do a proper A/B comparison.
Proper level matching, flat FR, phase adjustments (if applicable), bypassed amp processors and low noise are the key element most of the time.

In short words, all that the RC challenge tells you is that amps when measured the same do sound the same.


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## ddsBMW (May 31, 2007)

I use alpine PDX amps. I cannot tell a difference for my fronstage or sub. I used to have a JL 450/4 for my fronstage. If the amp is properly designed you should not be able to hear a difference. I like how people say they can tell between class a/b and class d amps when used for full range or sub frequencies, then when I actually listen to their system it sounds like crap. I don't think you can tell in a car and I am not sure you can in home audio either.


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## cvjoint (Mar 10, 2006)

89grand said:


> Class D amps ARE NOT limited to 200hz. I don't even think DS-21 said they where either, he just used a hypothetical number, I think. For instance, my JBL GTO 600.1 is limited to 320hz according to the specs. Way beyond what any reasonable person would use a mono sub amp for.





300Z said:


> Class D is not a band limited topology, the reason most car audio D class amps are is due to cost, a proper full range class D amp is both expensive and more difficult to build/design.


So for all practical purposes the 500.1 class D I tested did not extend to 20khz or for that matter 45khz as the A/B. I was not implying 200hz was the limit but rather a precautionary filter.



ddsBMW said:


> I like how people say they can tell between class a/b and class d amps when used for full range or sub frequencies, then when I actually listen to their system it sounds like crap.


You listened to my system lately? Interesting...


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## npdang (Jul 29, 2005)

Yes, amps do sound different. And yes, we do have a relatively good understanding of why. And no, just because you can hear differences between amps doesn't mean you can determine what causes those differences.


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## ddsBMW (May 31, 2007)

cvjoint said:


> So for all practical purposes the 500.1 class D I tested did not extend to 20khz or for that matter 45khz as the A/B. I was not implying 200hz was the limit but rather a precautionary filter.
> 
> 
> 
> You listened to my system lately? Interesting...


I wasn't refering to you or your system. I'm sure your system sounds great. I have just been around a lot of people that have "super hearing" and can hear some crazy things. I still feel that with decent amps, properly built class D amps or class A/B amps, proper gain settings, level matching and low noise you cannot tell the difference in a car. Especially with a sub.


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## chad (Jun 30, 2005)

300Z said:


> Class D is not a band limited topology, the reason most car audio D class amps are is due to cost, a proper full range class D amp is both expensive and more difficult to build/design.


Careful there buddy! They are *VERY MUCH* band limited by design, just like the CD format or any other digital format, there is a very steep LPF filter to filter out the switching artifacts.. well.. um actually make it smooth analog again  Where that LPF filter is placed is up to the designer. The higher the more money. Granted on full range amps this is higher than we can hear and it's a moot point but it is limited on purpose.


Chad


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## MarkZ (Dec 5, 2005)

cvjoint said:


> Things don't add up though. Why would the manufacturer cut corners so much on the D? Both amps are sold for the same price yet the D uses a smaller heatsink and it is probably altoghether cheaper to manufacture. If they were to push the profit margin it would be on the A/B cousin where marginal profit is smaller. I know manufacturer sheets are not 100% accurate and unbiased but within their own lineup and without a reason I don't see how the A/B would be grossly underrated.


It's not a matter of cutting corners. All manufacturers cut corners for all their equipment. Nobody uses the absolute best parts, best designs, best thermal arrangement, biggest heat sink, etc. Why? Because it's unnecessary. Also, part of the allure of class D is its small footprint.

This isn't to say that class D is worse than B because of its smaller heatsink. That isn't true either, because the amp by its very design is going to generate less heat. But compromises are made based on certain assumptions about the buyer's listening preference (eg. people listen to music and not continuous sine waves). It's true for all amps.

If you truly wanted to design two amps that differ only in class, then you'd need to build the same power supply, use the same output devices, the same heatsink, the same preamp circuitry, etc. I don't think you could say that they did that in your two Polk amps.



> One note...if the D is limited at 200hz isn't that because inherently this class would have issues with higher frequency reproduction? Would it be wrong to say a narrow frequency band is a characteristic of class D?


No, it's inherent in their design. But there are full range class D amps available.


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## t3sn4f2 (Jan 3, 2007)

*Re: class a/b vs class D*?

class D for me at any FR range that draws alot of current. I'll leave it at that.


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## chad (Jun 30, 2005)

t3sn4f2 said:


> *Re: class a/b vs class D*?
> 
> class D for me at any FR range that draws alot of current. I'll leave it at that.


I think that totally sounds like a plan


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## 300Z (Mar 20, 2005)

chad said:


> Careful there buddy! They are *VERY MUCH* band limited by design, just like the CD format or any other digital format, there is a very steep LPF filter to filter out the switching artifacts.. well.. um actually make it smooth analog again  Where that LPF filter is placed is up to the designer. The higher the more money. Granted on full range amps this is higher than we can hear and it's a moot point but it is limited on purpose.
> 
> 
> Chad


By not being band limited I meant not in the audible bandwidth. Guess I should have been a bit more specific...


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## chad (Jun 30, 2005)

300Z said:


> By not being band limited I meant not in the audible bandwidth. Guess I should have been a bit more specific...


Just teasing  

After a thread goes to 10 pages I'll get out the magnifying glass


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## cvjoint (Mar 10, 2006)

I think we should settle this the old fashioned way
















Get ready for MORTAL KOMBAT!


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## ddsBMW (May 31, 2007)

cvjoint said:


> I think we should settle this the old fashioned way
> 
> 
> 
> ...



I'll take Sub-Zero. LOL


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## cvjoint (Mar 10, 2006)

ddsBMW said:


> I'll take Sub-Zero. LOL


I'll take Milena and "melt" you!


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## Guy (Feb 16, 2006)

cvjoint said:


> I think we should settle this the old fashioned way
> 
> 
> Get ready for MORTAL KOMBAT!



Oh man, before I scrolled down I was afraid I was going to see Richard Clark brought in to this!


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## t3sn4f2 (Jan 3, 2007)

G Rahn said:


> Oh man, before I scrolled down I was afraid I was going to see Richard Clark brought in to this!


I heard he's unbeatable.


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## Abmolech (Nov 2, 2006)

Rock, paper scissors?

Very interesting discussion. The advantages of the D class power amplifiers seem over whelming, my only comment is it somewhat less "refined". AB topology seems well established and runs it coarse, where D class and its variants still appear to have more refining and progress available.The long term does not look promising for AB.


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## kyheng (Jan 31, 2007)

Maybe 1 should test the amps on longer run hours to see which is better, say 5hours. Will class AB amps(less effiecient and gets hot) still sound the same when it is cold compare to class D amp. For my point of view, I have only owned a class A amp(for my front and rear speakers) and a class D amp. After 1 hour run, the class A amp's temperature can used for boiling water and the class D amp still warm.


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## thehatedguy (May 4, 2007)

What "class A" amp did you use?


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## kyheng (Jan 31, 2007)

Lightning Audio, I know it is a bad amp in US, I bought it when I still not yet know this forum. In my country the Bolt series can sell upto USD600.


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## ƒÆ§tÇµm (Feb 5, 2011)

How about some Halloween necromancy? Rise from the grave my precious. :skull: 

SQ: A>AB >G/H>D>C


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## cvjoint (Mar 10, 2006)

I wish I could go back and delete all my amplifier talk. I ran some half assed tests and went all out bitching about it years ago. Well, maybe some folks will go back and see my silliness and pick a different route. These posts will be my scarlet letter.


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## BuickGN (May 29, 2009)

cvjoint said:


> I wish I could go back and delete all my amplifier talk. I ran some half assed tests and went all out bitching about it years ago. Well, maybe some folks will go back and see my silliness and pick a different route. These posts will be my scarlet letter.


If you wouldn't mind explaining, what changed? This is interesting to me as I have a pair of class D amps under the seats.


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## cvjoint (Mar 10, 2006)

BuickGN said:


> If you wouldn't mind explaining, what changed? This is interesting to me as I have a pair of class D amps under the seats.


I did these tests where I had the same brand amplifier in class D trim and A/B. The A/Bs always sounded better to me while swapping, but as many have mentioned here the tests were flawed in a major way. It wasn't just the class that changed it was an entire amplifier. The point was simple but evaded me for years. The point is none of my tests were proper experiments, many variables changed so I can't really say the class makes a difference. 

For all practical purposes I don't think there is any evidence out there that different classes sound differently when designed just as well. RC's challenge remains the best test to date so I'll follow those findings religiously until someone designs an experiment that's better and finds something else. 

My beef with a lot of acoustics experiments is that they have very low sample sizes. It's not uncommon to find experiments with less than 20 subjects and as a applied economist that is a bit troubling. Nonetheless the best experiment should be noted and that's RC's. I'd be happy to run a Class D that has the same power, THD+N, and frequency response yet is more efficient than a Class A.


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## BuickGN (May 29, 2009)

Thanks!


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