Amplifier classes AB vs Digital: noticeable difference when hooked up to a subwoofer?

[3.5Max6spd 10+ year member]

Unless RC has changed his test, the stipulation was that you couldn't reliably distinguish between two amps of the same topology. Class D and Class A/B are different topologies.
From a purist standpoint, if SQ is your goal, avoid Class D amps. The are not linear amps. They approximate the signal fed to them, they do not truly reproduce it. The more efficient the amp the grosser the approximation. As mentioned, you probably won't be able to note a difference at the subbass freqs, but you will definitely want a low cutoff freq for the sub.

The problem that you run into is that if you want a lot of power for your sub-stage, you almost have to go with a Class D. The limiting factor is the efficiency of the Class A/B design. Best case you are looking at 50%. You can approach 85% with a good Class D. That is a huge reduction in load on the car's electrical system for the same amount of power. If you are looking at something in the 600W+ range and you don't want to go through the hassle of major reinforcement of the car's charging system, you would be hard pressed to go with anything other than a Class D IMO.

Me personally, I'm a SQ guy. I don't own a Class D amp and I can't forsee myself buying one. I don't need large amounts of power and I prefer fidelity over power. In a low powered system efficiency is not of paramount importance so I'm not that willing to compromise linearity for a little savings in current consumption that doesn't make any difference in my car.

Well said..

 

[squeak9798 5,000+ posts]

Unless RC has changed his test, the stipulation was that you couldn't reliably distinguish between two amps of the same topology. Class D and Class A/B are different topologies.

Any amplifier classes are allowed. A vs A/B. A/B vs D. A/B vs A/B. Read through the rules I posted earlier. He does not state that the amplifiers being compared must be of the same topology. Any amplifier is fair game as long as it meets the rest of the criteria (noise, distortion, etc)

The point was to distinguish what does and does not have an audible affect of the "sound quality" of an amplifier. This includes amplifier topology.

To quote werewolf, the purpose of the amplifier challenge is to establish a hypothesis that;

The standard amplifier tests of power, gain, frequency response, noise & distortion completely characterize an amplifier's sound. Therefore, any two amplifiers that measure the same, will sound the same.

So far no one has disproved this hypothesis.

Quote take from;

http://forum.elitecaraudio.com/showthread.php?threadid=123226&pagenumber=3 - great thread to read on the subject.

From a purist standpoint, if SQ is your goal, avoid Class D amps. The are not linear amps. They approximate the signal fed to them, they do not truly reproduce it. The more efficient the amp the grosser the approximation. As mentioned, you probably won't be able to note a difference at the subbass freqs, but you will definitely want a low cutoff freq for the sub.
...

Me personally, I'm a SQ guy. I don't own a Class D amp and I can't forsee myself buying one. I don't need large amounts of power and I prefer fidelity over power. In a low powered system efficiency is not of paramount importance so I'm not that willing to compromise linearity for a little savings in current consumption that doesn't make any difference in my car.

You are more than welcome to find a full range Class D amplifier to put up against your favorite class A/B or pure class A in order to disprove the above hypothesis. But thus far, out of thousands of tests, no one has.

 

[FoxPro5 5,000+ posts]

Just run your sub off your head unit....better yet, bridge all 4 channels to get teh supa powa! //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

 

[squeak9798 5,000+ posts]

guys---the sound quality issue of amps once again raises its ugly head----i ahve no reservations of including class D amps in my amp challenge and have done so in the past---for years dave and i have been strong proponents of class D as it just makes sense---yes it is harder to do class D at higher frequencies but not impossible---its just not as important as we usually reserve most of our power for the lows anyhow----[...]........RC

//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[FoxPro5 5,000+ posts]

Taken directly form Zapco's Competition line manual....not pushing the product or anything //content.invisioncic.com/y282845/emoticons/up2something.gif.dd110ecf3ae4b76050d87598f2f8de7c.gif

Class D for the Audiophile

​

We saw our first Class D amp in 1975. Numerous companies have

been trying since then to design and build a full range Class D, with very

little success. Class D amps have had so much noise and distortion that

they destroy mids and highs. Even when used strictly as bass amps

they’ve been dangerous. Competitors who use class D amps in SPL cars

invariably blow out all their woofers when they hit those high numbers.

This happens because of the extreme distortion the class D amps have

been putting out when they’re driven hard. This may be acceptable to

professional competitors, who get their speakers for free, but for the noncompetitor

who has to pay for them out of their own pocket, it can be a real

nightmare. Not to mention that most of us want to be able to listen to

music in our cars and need an amp that sounds great on everything, not

just woofers.

 

Welcome to ZAPCO’s world! Where dreams of Class D power, and full

range sound quality come true.

 

The ZAPCO C2K 9.0XD is the ultimate car audio amp in so many

ways. The first, of course is power. With over 2000 watts RMS into either 2

Ohms or 4 Ohms, and a chassis only 18" long, it’s easily the most powerful

amp of its size. But that’s only the start of the story. The 9.0XD has the

most advanced microprocessor control system ever offered in a car audio

amplifier. This amp has a serial port that allows it to talk to other amps, to

a PC, or even to your car. It can be programmed to control its own power

output and clipping levels. The microprocessor system in this amp will be

the heart of our new systems as we move into the realm of full digital, from

source to speaker output. With all of it being brought to you by ZAPCO.

When you’re ready for the ultimate in car audio, ZAPCO has your

product.

​

 

[whtxblazer02 10+ year member]

and a few complaints about Fosgates heating up too much and going into protection mode...

I ran a 800a2 for about 3 years on 2 HE2 12s. The amp got hot, but I have never had a RF amp cut out on me. It stays over 95 degrees here in the summers also. More than likely the problem was user error. The 800a2 is not 2-ohm mono stable. I had dual 4-ohms subs, so it was putting out 800 wrms X 1 @ 4-ohms.

 

[thch 10+ year member]

yay thanks a lot for tha answer... i got one question thou... yu said you had a 900w RMS A/B class amp and then another 400w RMS D class and you said one of them sounded tighter and cleaner, but i want to know with which one you felt this difference? for what you said both sounded better on different aspects.. can you tell me what were the differences and in which sense one amplifier sounded better than the other?

no, it was merely switching from one amp to the other. my classD amp broke, so i got a new amp. everything was good and the class AB was SOOO much nicer then the class D. then later i got sick of dimming headlights, so i fixed the class D amp and put it in. i was shocked at how much nicer it sounded. in short, it was really the new gains and such each time, as well as the added attention to detail that one takes during tuning a system.

 

[Prowler573 5,000+ posts]

I think the important thing is that you are happy with your system, who cares what the reason is or what anyone else thinks //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

I think this is exactly right and should be the [/story].

...all that he said...

I wanna see guy duke it out with thylantr. Both you and thy impress the heck outta me as you both obviously know more about this ish than I ever will.

 

[phantom240 5,000+ posts]

okay, personal experience here.

now im no professional when it comes to efficiency of AB vs. D class amps and all, and im not gonna try to bombard you with this info and that.

I have an alpine MRV-1507. It runs my 2 12s. This amp has NEVER shut down on me. It is loud as hell for its "rated" power. I love it. It has been the most reliable amp ive ever had. I have no experience with the other amps you want, and im not gonna disrespect them in any way because of it. I think that for n00bs and the somewhat experienced like me, this is an awesome amp to get some power to your subs. Very clean bass. I think you will be very happy with one of these amps. I would sell you mine, but i love it like a brother.

 

[faulkton 5,000+ posts]

is it a a/b or a D? Seems like you should include that info in your post. someone as experienced as you should know that. Newbs dont wanna look up your amp.

 

[phantom240 5,000+ posts]

not to be an ***, but did you even read the whole first page?//content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif I quote from the 2nd post

for AB class would you recommend Fosgate 800a2 or the Alpine MRV-1507??

So that would tell most ppl, provided that they have basic english skills, that the 1507 is, in fact, an AB amp. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[faulkton 5,000+ posts]

yeah i read the first page last week. I had forgot that. Including that quote in your post wouldnt have been to hard. Just a suggestion.

 

[helotaxi 5,000+ posts]

Any amplifier classes are allowed. A vs A/B. A/B vs D. A/B vs A/B. Read through the rules I posted earlier. He does not state that the amplifiers being compared must be of the same topology. Any amplifier is fair game as long as it meets the rest of the criteria (noise, distortion, etc)

That's what I remember. I couldn't remember if he had included Class D. I know the premise of the "challenge" and fully agree that if they measure the same, they sound the same "a watt is a watt" in a manner of speaking. My point is really that a Class D typically measures like *** and sounds like *** when you are trying to get power out of them and they clip very harshly when you do drive them too far. I would say that they sound fine "in their linear range" but they aren't linear so that is moot. They sound fine when not driven hard, but who never drives their amps hard? I'm not trying to start an argument because there isn't a point to argue. Physics rules the day. I guess my point is that you can't tell the difference between two amps with high distortion and most mass produced D class mono amps have pretty high distortion and a relatively high noise floor.
I only know of 3 full range class D amps including the Zapco described above. Blade Audio made a whole series of them in the early 90's and Xtant makes one right now. The problem with these are that they sacrificed efficiency to better approximate the signal. They have lower distortion than the big inexpensive mono amps but make less power in most cases and draw more current doing it. They ARE more efficient than a Class A/B but not by much and for the modest power they put out the savings in current consumption isn't that much.

The point was to distinguish what does and does not have an audible affect of the "sound quality" of an amplifier. This includes amplifier topology.
To quote werewolf, the purpose of the amplifier challenge is to establish a hypothesis that;

The standard amplifier tests of power, gain, frequency response, noise & distortion completely characterize an amplifier's sound. Therefore, any two amplifiers that measure the same, will sound the same.

So far no one has disproved this hypothesis.

And no one ever will. I can use an EQ to make a really expensive set of speakers sound like trash, but no ammount of EQ will make a crappy set sound good. You can't hear a difference that you can't measure, but you can measure differences in plenty of amps that are clearly audible.