# Highest damping factor amplifier



## e30m3 (Jun 9, 2006)

I need an amp for mid bass speakers and I want one with a very high damping factor. I am running all active crossovers, so slew rate and things do not matter. I already know that damping factors above 150 are considered inaudible but my entire is overkill, big time, so I need to continue the trend to make it all sound right together. The speakers are 8 ohms and I would like an amp that has a damping factor of upwards of 600 at 4 ohms and pumps out at least 75 watts over 2 channels. Price is unimportant at the moment but I used stuff is always better for me. Any thoughts?


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## Diru (May 23, 2006)

look for a Hafler.


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## jay (Sep 12, 2005)

while i personally don't see the point....it does seem that zapco has quite a few offerings you could look into.


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## zfactor (Oct 19, 2005)

massive audio has some at 2000.. the ca series


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## e30m3 (Jun 9, 2006)

jay said:


> while i personally don't see the point....it does seem that zapco has quite a few offerings you could look into.


I am confused as to how you could miss the point? And the new reference 750.2 is the one I was looking at from Zapco. What is the old AG line equivalent to this, is it the AG750?


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## cvjoint (Mar 10, 2006)

I though nothing above a 10 or 20 damping factor is really audible. There are plenty articles online that try to prove it. 
I use polk momo's. I called their service center and they told me the damping is 800 at 4 ohms for the 4 and 2 channel amps ( class ab ). A very good amp for the money.


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## badlieu (Jul 13, 2005)

Diru said:


> look for a Hafler.


http://ampguts.realmofexcursion.com/Hafler_MSE88tn/

Here's pics of my little Hafler


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## ca90ss (Jul 2, 2005)

Also remember that as impedance doubles so does damping factor so an amp with a damping factor of 600 at 4ohms will be 1200 at 8ohms


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## mvw2 (Oct 2, 2005)

Interesting read:
http://www.bcae1.com/dampfact.htm


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## MarkZ (Dec 5, 2005)

e30m3 said:


> I need an amp for mid bass speakers and I want one with a very high damping factor. I am running all active crossovers, so slew rate and things do not matter.


Many would argue that the damping factor doesn't matter either. Check out the following link, it may make your search considerably easier:

http://www.diyspeakers.net/Articles/Richard Pierce DAMPING FACTOR.pdf

According to this data, your 150 number is an overestimate, to the point where it pretty much makes the spec meaningless. Personally, I'd look towards other amplifier attributes to go the "overkill" route. Like overkill with power, noise and distortion performance, etc. Even though those parameters reach a point of diminishing returns too, they're much more meaningful specs.


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## WLDock (Sep 27, 2005)

badlieu said:


> http://ampguts.realmofexcursion.com/Hafler_MSE88tn/
> 
> Here's pics of my little Hafler


O.M.G!,

I had several of those amps back in the day. Those little suckers were built like tanks. Powered many systems for myself and friends with them. Brings back memories of my early days of car audio.


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## e30m3 (Jun 9, 2006)

I personally believe that damping factor may be inaudible above 50 or 80 just like some people argue for one hit, or for one specific instant, but for continued use the amp must maintain speaker control and the higher damping factor indicates bass speaker control. Amps that cost a lot for home or car usually have high damping rates from the high quality components that they use, so I believe damping factor is crucial in an SQ system, maybe not in SPL because its much easier to make a giant 2000 watt amp with a small damping factor then it is to make a 400 watt amp with a very high damping factor.


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## MrH (May 27, 2006)

As mentioned already, Zapco. C2k 6.0 would give you the power you're looking for at 8ohms.


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## MarkZ (Dec 5, 2005)

e30m3 said:


> I personally believe that damping factor may be inaudible above 50 or 80 just like some people argue for one hit, or for one specific instant, but for continued use the amp must maintain speaker control and the higher damping factor indicates bass speaker control. Amps that cost a lot for home or car usually have high damping rates from the high quality components that they use, so I believe damping factor is crucial in an SQ system, maybe not in SPL because its much easier to make a giant 2000 watt amp with a small damping factor then it is to make a 400 watt amp with a very high damping factor.


Damping factor is, simply stated, another way to express the amplifier's output impedance. For most amplifiers incorporating negative feedback, the output impedance is close to zero, making the damping factor these really high values that you see in the majority of amps (negative feedback is a circuit design strategy in which the output is fed back to the input in order to "correct" for various nonlinearities picked up along the way -- it's toned down at higher frequencies for stability purposes, which is why distortion usually increases and DF decreases at high frequencies). So basically, seeking out an amplifier with a damping factor of 800, for instance, isn't going to give you any inherent benefit over one with a damping factor of 50 -- in both cases, the output impedance is pretty much zero.

The funny part is when you run into so-called audiophiles who insist that negative feedback is a bad thing or who criticize solid state components in favor of tubes, and as a result end up with damping factors close to single digits. Those are "audiophile" amps.  

Overall, damping factor is mostly governed by the amount of global negative feedback used and any type of LC filters and zobels at the output, and possibly (I'm not sure) the emitter resistors that join the output transistors. Make the negative feedback high and you'll increase the damping factor. However, there's a downside too. You could introduce instability if you don't roll off your negative feedback sharply enough at high frequencies. Also, you could eliminate the output filters and such and probably improve your damping factor, but your protection is compromised and some loads could really mess with your amplifier. If you lower the emitter resistors, you might be able to raise the damping factor, but in doing so your output protection circuitry may not be optimal (depending on the design strategy) and your distortion numbers could potentially rise. 

As you can see, there are compromises in the design to achieve high damping factors. So once it's already good, I think it's better to shift the focus to other parameters, such as distortion, noise, and reliability. Some of these are quantifiable or can at least be deduced merely by looking at the build quality of the circuit -- there are sites online that will show you the internals of amps.

Again, I'm not trying to dissuade you from looking for high damping factor. Just keep in mind that damping factor isn't merely the result of attention to detail or high quality components -- rather, it's the consequence of the design, and the designs that yield the ultra-high damping factors aren't necessarily the better ones.

Personally, when I'm looking for an amp, I believe the best test is the weight test.


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## Eastcoast (Mar 26, 2005)

You are wasting your time and $$ buying an amp based on that. Anything above 100 is fine.

You want to hear a difference, buy significantly more power, the headroom is where you will hear a difference. An amp with 75 watts and a damping factor of 8,000,000 will be outdone by a quality amp that does a legit 150 and a damping factor of 100. 

I agree with your overkill theory, but what you are doing is the equivalent of buying a car based on how many cupholders it has. Once you pass a certain point, on a practical level, it is absolutely useless. 

By all the power you can afford, not the damping factor.


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## chad (Jun 30, 2005)

Add to what Mark Said....

The Damping factor rating is taked at the output of the amplifier. Take it at the voice coil of the driver and the playing field gets evened out REALLY quick!

Chad


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## FocusInCali (Jul 3, 2005)

Arc Audio 2500XXK is the amp I wanted for 8 ohm midbass duty.
http://www.arcaudio.com/arc-05/amplifiers/xxk_2500.htm
and
http://www.arcaudio.com/arc-05/pdf/xxk_amp.pdf

They usually go for around $400 used.
Estimate about 140w/ch at 8 ohms.

The amp I had tested 540w/ch at 2 ohms at .005 thd.

That'll give you plenty of headroom. Arc specs over 2000 dampening for this amp, but as said, headroom is what you're really after.

I also like that Arc amp gains start at 2.5v, so you can keep them turned all the way down.

The same amp internally is the older case design 2500CXL, but it may run warmer.


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## invecs (Jul 30, 2005)

I've read that the length of speaker cable used affects damping factor. I think it wouldn't hurt using an amp with a higher damping factor.

I also remembered emailing Butler that I find the td750 that I had before to be sloppy in midbass...he emailed back and suggested using 8ohm speakers to improve midbass control. From what I understand, damping factor increases by using a higher load.


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## e30m3 (Jun 9, 2006)

Good responses guys. So the perfect amp for this would be one with about 150 watts into 8 ohms, to give me my headroom therefore not clipping the amp and bringing unnecessary distortion, also this amp should have a low THD rating, something around .01% to make sure the signal is clear, and that has a damping factor somewhere around 800 at 8 ohms. Also the amp should have good channel seperation and has good sn ratio. Am I correct here or am I missing something?


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## e30m3 (Jun 9, 2006)

Here are some amps I have been looing at:
Linear Power 2502IQ
Hifonics Zeus VIII
Hafler
Old school Alphasonik
I will look at the Arc right now, but what do you guys think of these amps?


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## MarkZ (Dec 5, 2005)

invecs said:


> I've read that the length of speaker cable used affects damping factor.


It contributes to the overall effect, in that it's one of the two components used two calculate damping factor (which is defined as the ratio of amplifier output impedance and load impedance). 

Think of it this way: all amplifiers have a certain impedance associated with their output stages. It's like they have a resistor in series with the output. One of the things it's going to do is attenuate the signal a little bit. How much? Well, according to the voltage divider rule, it's going to depend on the impedance of the load. To the amplifier, the whole circuit - speaker wire, connectors, voice coil, etc - is the load. So yeah, if you use higher impedance wire then you're going to change the load. 

The debate comes when you ask how much the amplifier's "resistance" is going to shape the outcome. For most reasonable values of damping factor, not much. I say this basically because the output impedance of a "typical" amplifier is usually on the order of a fraction of an ohm. The speaker wire itself can exceed that. The speaker's impedance is obviously going to be much higher than either of those, and in fact the impedance changes with temperature. This fluctuation in impedance can potentially be on the order of several ohms, thereby muddying the influence of the amplifier output even more.

Altogether, it's just another one of those specs that amplifier designers have made virtually irrelevant due to progress in engineering. Unfortunately, they're not quite as close to perfection in the realm of speaker design...



> I also remembered emailing Butler that I find the td750 that I had before to be sloppy in midbass...he emailed back and suggested using 8ohm speakers to improve midbass control. From what I understand, damping factor increases by using a higher load.


Yep, it increases with higher impedance loads. However, lots of things change when you change the load. Output filter characteristics can change the signal differently; THD can vary considerably with impedance; and of course the speaker itself is different..


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## MarkZ (Dec 5, 2005)

e30m3 said:


> Good responses guys. So the perfect amp for this would be one with about 150 watts into 8 ohms, to give me my headroom therefore not clipping the amp and bringing unnecessary distortion, also this amp should have a low THD rating, something around .01% to make sure the signal is clear, and that has a damping factor somewhere around 800 at 8 ohms. Also the amp should have good channel seperation and has good sn ratio. Am I correct here or am I missing something?


Most of all, it should have a good reputation. Specs only go so far, and they're always measured differently from manufacturer to manufacturer, so don't go overboard analyzing them. I'd look for an amp that people are raving about and what it is they like about it (and how long they've owned it!).


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## MarkZ (Dec 5, 2005)

e30m3 said:


> Here are some amps I have been looing at:
> Linear Power 2502IQ
> Hifonics Zeus VIII
> Hafler
> ...


How old school do you mean on the Alphasonik? I've owned a couple in the past (mid-nineties) and had pretty good luck with them. If you're after an "overkill" amp though, you may want to look elsewhere. These were very good budget amps with relatively small footprints, but probably not what I'd consider to be a balls-to-the-wall amp. 

If you don't mind the older stuff, the old Rockford and PPI amps come highly regarded by many (including me) and not terribly difficult to find. I still own an ESX Quantum series (the Zed-built ones, before their reissue) that I'll never part with but you can still catch on ebay every so often. I also really liked the Kicker ZR-series amps. I regularly beat the hell out of ZR360's and ZR1000's without a peep from the amps. If I was in the market for an amp today, I'd almost certainly look for some from yesteryear. Good prices and good performance.


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## chad (Jun 30, 2005)

MarkZ said:


> It contributes to the overall effect, in that it's one of the two components used two calculate damping factor (which is defined as the ratio of amplifier output impedance and load impedance).



And beings that the output impedance of a solid state amp WITHOUT OUTPUT TRANSFORMERS (all car amps I have seen) is a fraction of an ohm the fraction of an ohm the cable has GREATLY influences the damping factor. It's a ratio! Also.... DF is NEVER rated at a frequency, remember that there is more than RESISTANCE at play, we seal with impedances, even within the amp for the most part.

Shove any modern SS amp down 25' of 12Ga and the damping factor is going to become a negligible spec.

Chad


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## zfactor (Oct 19, 2005)

^^^^^ agreed man.. well said


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## toolfan91 (Dec 7, 2005)

Ah how I love this forum, I learn something new every day  Definitely my favorite forum!


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## cvjoint (Mar 10, 2006)

mvw2 said:


> Interesting read:
> http://www.bcae1.com/dampfact.htm


even more interesting when you plug in values at the bottom calculator. For example I've run my seas lotus rw165s from the same amp 800 damping at 4 ohms 75 watts per channel. I've connected it first as one per channel, the amp running at 4 ohms, then briddged the amp to increase power but lowered df and imp. at 2 ohms. According to the chart I went from a df of 58.5 to 29.25. I DID notice a change in speaker control when I made the change and missed the 4 ohm configuration even though it had less power. for me THIS site works bcuz I can actually back it up with real life results, unless I'm missing something. Time to buy 8 ohm Seas


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## Accurate_dB (Apr 1, 2020)

Sorry to ressurect an old thread. But there is simply no way to listen to every amp out there, let alone feel them. Personally damping factor should be felt and not heard. Secondly, people should pay attention to names. Amps can go mediocre when company's ownership change, and there are a lot to speak of. Also I think collector value is important too, like whether or not the amp is bespoke. Two names come to mind in car amps, Zef and Macmillan.


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