# Class A/B vs Class D amps?



## Juice75 (Sep 18, 2010)

Is there a sound difference between class A/B and class D amps for the front stage? I've seen a few quotes like: "I'd never run Focals off a class D" and "class G technology has class D efficiency and class A/B sound". So what's the difference in the sound?

The reason I ask is right now I have an Alpine PDX-5. Like everyone else here, I'm always looking for the next best thing. The amp I had before was an old Alpine V12 5-channel. When it blew and I switched to the PDX, the front stage sounded better, but the sub didn't have near as much depth. Seems like it gained punch, but lost the lows. I like running a 5-channel for simplicity, but sometimes wonder if splitting to a 4-channel and a mono would be better.

Bring on the opinions.  Oh, and I should add that I've also read on here "all amps sound the same". Although, I can say from my limited experience that that isn't true.


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## Hanatsu (Nov 9, 2010)

I've never heard a class D fullrange amp, been using A/B amps for all my setups and that have worked well for me. I've heard pure class A amps and I gotta say they produce a really refined sound. Never seen anyone using class D fullrange on the competions I've been at. Lots of people say D fullrange never can be as good as A - A/B. The more expensive D amps does probably sound great, but due to the fact that they are highfrequency switching amps I'd stay away from the cheaper (or older) ones at least to avoid high frequency distortion. Nowadays you get plenty of power out from a A/B amp so why buy an amp which may or may not live up to expectation


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## derickveliz (May 15, 2009)

I moved my front stage (*mids + tweets*) from a class *D* amp to a class *A/B*...

Also my sub-woofer from a *class D 400 watts* to a *class A/B 260 watts* and the difference is day and night.. *I'm glad I did!*

Both class D amps where over 8 years old, though! Technology it's much better this days, but that was my experience. I hope it helps

(o:


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## Morts (May 28, 2009)

I ran Class A-B for every system I have ever owned and still own even on the Sub stage and went to MMATS Class D and it sounds every bit as good. I think you would be hard pressed to tell that it was a Class D running my mids and highs. My 2 other cars still run Class A-B so I am not nut hugging one or the other, just an honest opinion, I was scared my SQ would suffer but it definitely did NOT with the Class D.


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## Juice75 (Sep 18, 2010)

Thanks for the info. Now let me put a little twist on it. My sub sounds great on parts of tracks that are just mainly bass. But as soon as the guitars and vocals kick in, it's like the sub level drops dramatically. This is something I never noticed with my old amp.

The PDX-5 recommends a 4GA power wire, and I'm only running an 8GA. Is the amp not getting enough power to push the sub when the fronts need more? Or is this theory completely out of whack?


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## cubdenno (Nov 10, 2007)

Juice75 said:


> Thanks for the info. Now let me put a little twist on it. My sub sounds great on parts of tracks that are just mainly bass. But as soon as the guitars and vocals kick in, it's like the sub level drops dramatically. This is something I never noticed with my old amp.
> 
> The PDX-5 recommends a 4GA power wire, and I'm only running an 8GA. Is the amp not getting enough power to push the sub when the fronts need more? Or is this theory completely out of whack?


my guess is that yes you may be starving that amp.

As for your question, if the amp is competently designed, then either class will work. If class D was crap, the pro audio world would not utilize them (and they have to produce actual truthful specs!!! not what we see in the car audio world)

as for amps sounding the same or swapping one amp for another, if one reads those threads on here, remember that swapping amps will automatically sound different unless you make sure the gain structure is the same within a quarter db. otherwise one amp is going to sound different just due to the differences in volume level.

The beauty of the Class D design is that it is more efficient, it's smaller watt for watt and now, pretty much indistinguishable from class A/b. Zapco, Alpine JL Kenwood... All have full range class D amps that are low distortion great sounding amps.. Or rather do what they are supposed to do and just provide more volume!


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## ChrisB (Jul 3, 2008)

This topic again? The bottom line is a quality full range class D amplifier will be nearly indistinguishable from a quality class ab amplifier in a lab setting. I'd be willing to bet that a very small percentage of those claiming to hear a difference really can while actually driving their vehicles.


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## ChrisB (Jul 3, 2008)

cajunner said:


> I'd agree, but only if taking the 3rd generation product into account.


I'm most definitely talking about modern day products like the Kenwood XR, JL Audio HD, JBL MS, and even Zed's new offerings. I was also impressed by the new Alpine PDX amplifiers and you'll rarely see me post anything good about them.

Of course, it took the 12v industry long enough to catch up to the pro audio world that has had full range available since 1998 or so. The car audio industry did such a great job at milking the class ab design for WAY longer than they had to. 

Now, if only the aftermarket would catch up to the automotive OEM manufacturers by offering head units with balanced outputs and amplifiers that take balanced inputs to the 12v consumer. Here it is 2010, and most of the aftermarket 12v products are still using RCA technology. That's OK though because they've given me enough justification to start building a car PC to replace those old school style RCA equipped head units that play those shiny disc like things.


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## Juice75 (Sep 18, 2010)

Yeah, sorry for bringing up an old topic. I didn't realize it had been beaten to death already. So looks like I'll stick with my PDX-5, and just upgrade the power wire to 4GA. I'm hoping one of these days to just quit messing with my system and enjoy it.


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