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Class D Amps - Anyone else having second thoughts?

#164
pgk said:
I submit that in a double-blind test, you (or the rest of us) would not be able to distinguish a Class D from a Class A/B, or other amplifier topology, whether tubes or solid state devices were used. I imply of course proper gain-matching.

oh god, here we go. i suggest you go ahead conduct just such a truly unbiased test and Then let's see what's what. don't use conjecture as you are here but do that test to put some teeth in your theory, or not. my reality, using that stuff in real world situations, has been very different than from just mere speculation...
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Did you ever wonder what the does?
 
#168
Craig_S said:
I found this: A = analog power amp (class AB); So, class D is digital? Forgive me. I'm trying to understand all of this.
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Markbass and some other companies call Class D 'digital', and various techs and engineers here and elsewhere agree or disagree with that to varying degrees. But strictly speaking, Class D stands for the next class after Class C, not 'digital' per se. And there are also many other analog classes besides AB.

You might try reading through the AmpFAQ link stickied at the top of the Amps Forum for a little more insight, or one or more of these:

http://www.bcae1.com/ampclass.htm

http://en.wikipedia.org/wiki/Electronic_amplifier

Link Removed
 
#170
Passinwind said:
Markbass and some other companies call Class D 'digital', and various techs and engineers here and elsewhere agree or disagree with that to varying degrees. But strictly speaking, Class D stands for the next class after Class C, not 'digital' per se. And there are also many other analog classes besides AB.

You might try reading through the AmpFAQ link stickied at the top of the Amps Forum for a little more insight, or one or more of these:

http://www.bcae1.com/ampclass.htm

http://en.wikipedia.org/wiki/Electronic_amplifier

Link Removed
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Yep there are class A through H and A2, AB1, AB2, and Doherty so far, and no doubt more to be invented. Arguably none of them are what I would term digital, though some involve switching devices. All of them use analog design principles.

What we commonly call AB here on TB is actually class AB1.

Hopefully that's enough acronyms for one thread, erm, sentence. :D
 
#171
seamonkey said:
The goal of a "head" is to create a signature sound for the maker - it doesn't matter what class of amp they use. The maker is coloring the amp/pre-amp to have a sound they think will sell.

A class-d power amp, is just that - it just amplifies. You, nor anybody can hear a difference in a true blind test.
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True and not so true. In our case, we worked on the preamp first and most of the initial listening was done through my studio setup using my trusty Beyerdynamic headphones. This helped me hear the nuance of the pre under a microscope, so to say. The goal was literally, as you pointed out, to create our signature sound.

With the power section, our engineers set up blind listening test with what we felt were the four best candidates. This consisted of two different off the shelf class D modules, a linear class H of our design, and a class A/B of our design. I can tell you without a shadow of a doubt, that the preamp sounded and "felt" quite different through each power section. Personally, I was able to pick out the class D modules every time. IMO, they add a extremely fast response and add a certain liveliness (from what we can tell is some extra upper harmonic content) to the sound that was obvious. Better or worse? No, just different.

One thing to note here is that most players tend to associate light weight with class D. Most of the weight saving is actually accomplished by the addition of a SMPS, not by the actual amplifier topology. A perfect example is the MarkBass gear which uses class A/B with a SMPS.
 
#174
pgk said:
[Invalid or Expired Link Removed]

that amp is class a/b with a non-switching supply and weighs 7pounds? well i stand corrected then, but my opinion of that amp is the same, i just don't get the hype surrounding them.
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No, the LMII and LMIII have a switching power supply, with a class AB power amp section. You can tell just by eyeballing the thing with the lid off.
 
#175
Handyman said:
No, the LMII and LMIII have a switching power supply, with a class AB power amp section. You can tell just by eyeballing the thing with the lid off.
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aha i see, thanks. in my limited experience with smps amps i've always walked away feeling they were lacking the "heft", for lack of a better term, of traditional designs. tube or ss doesn't matter here, that's a different discussion and yeah i'm talking about an intangible. but take an amp with iron in it and a trad power supply and compare; that is the sound i'm after and i just don't hear it from the smps designs i've heard. they sound strangely hollow, super fast and kind of plastic-y to me, again for lack of a better term. of course ymmv and jmo

i'm not trying to piss on anyone's wheaties here. i saw the op's original question and commented on my feelings about these things. and granted i certainly have'nt tried 'em all, but so far the verdict is that i'll pass on 'em
 
#176
You being an Ampeg artist should check out their SVT7... Dino says he likes his alot..


Since Ampeg disbanded St Louis Music, and foolishly let "Doc" (my artist rep) go, I have no interest in their products for the most part. I'm resigned to the fact that I will be paying for my own gear, and would like to support a smaller, made in the U.S. company if possible. A lot of the great people at SLM went to other companies, and the personal touch is what brought me to them in the first place.
 
#177
R Baer said:
True and not so true. In our case, we worked on the preamp first and most of the initial listening was done through my studio setup using my trusty Beyerdynamic headphones. This helped me hear the nuance of the pre under a microscope, so to say. The goal was literally, as you pointed out, to create our signature sound.

With the power section, our engineers set up blind listening test with what we felt were the four best candidates. This consisted of two different off the shelf class D modules, a linear class H of our design, and a class A/B of our design. I can tell you without a shadow of a doubt, that the preamp sounded and "felt" quite different through each power section. Personally, I was able to pick out the class D modules every time. IMO, they add a extremely fast response and add a certain liveliness (from what we can tell is some extra upper harmonic content) to the sound that was obvious. Better or worse? No, just different.

One thing to note here is that most players tend to associate light weight with class D. Most of the weight saving is actually accomplished by the addition of a SMPS, not by the actual amplifier topology. A perfect example is the MarkBass gear which uses class A/B with a SMPS.
Click to expand...

I should say properly conducted, gain matched, double blind test.

There are some clubs and groups that have done testing between various power amps and there is no statistical difference. One example:
http://www.matrixhifi.com/ENG_ppec.htm
(This particular one didn't include a class-d)

It can't of course prove that there is not someone with golden ears that can hear better than the average person, or others who can hear artifacts that really are not part of the goal of the amp. For example test subjects use to hearing records crackle and pops like CD's with added crackle and pop pre-recorded.

SMPS do save a lot of weight and energy, but class-d saves more weight as you don't need big heat sinks for the amp itself.
 
#178
seamonkey said:
I should say properly conducted, gain matched, double blind test.

There are some clubs and groups that have done testing between various power amps and there is no statistical difference. One example:
http://www.matrixhifi.com/ENG_ppec.htm
(This particular one didn't include a class-d)

It can't of course prove that there is not someone with golden ears that can hear better than the average person, or others who can hear artifacts that really are not part of the goal of the amp. For example test subjects use to hearing records crackle and pops like CD's with added crackle and pop pre-recorded.

SMPS do save a lot of weight and energy, but class-d saves more weight as you don't need big heat sinks for the amp itself.
Click to expand...

Totally different set of listening test, as that particular test involved home stereo gear fed pre-recorded music.. Our test consisted of the our pre amp being switched into the various power amps and the output volumes matched. We then played bass through each "complete amplifier" into our 212 bass cabinet, as well as a Bergantino AE410.

Trust me, 30 years of playing in loud rock bands has left my ear anything but golden, but fed a signal from an live instrument and played through a bass cabinet, the difference in various power sections were quite obvious to everyone. Besides the sound of the instrument, there are variations to the overall "feel" of the sound, as well as variations in how the amplifier reacts with the speakers and if your'e changing how the amplifier is reacting with your speakers, you are also changing how you react with your instrument. Just ask guys that continue to cart around an extremely heavy Crest CA9 to their gigs why they bother and I'm sure you will get the same response every time. Nothing else sounds or feels quite like it.
 
#179
There was an thread last year from a CA9 believer that just didn't have the gains matched. The CA9 versus a properly designed - SMPS powered class-ab - is like comparing power chords. If a class-d with SMPS has similar measurements, beyond that of human hearing, young or old - it would be highly suspicious that a true double blind test that someone could hear or feel a difference.

If there was a "feel" difference, it can be recorded, it can be measured. You can capture the input signal and compare it to the output. The difference minus the obvious power gain is the coloration.

The protocols for the double blind is to then investigate why there was a statistical difference if there was one. Measurements can do this.

Popularity wins out over science, over and over. Musicians choice, word of mouth, win out over any real measurements. People like it when authority dismisses the science.

Many manufacturers are having great times with class-d.
There's a few variations in techniques, and along with SMPS it's leading a new round of amps that seem very popular. It will be hard to sell the old heavy stuff to anyone on top of things.
 
#180
I have designed class AB power amps with SMPS and conventional power supplies, and with the same amp design, the difference between the two supplies was not at all easily noticeable. This was with the NeoPak 3.5 and that convinced me of the future of SMPS. The SMPS was designed to emulate the characteristics of a traditional supply, but that wasn't a big deal. The point here is that the supply was the only difference.

So, identical amps with different supplies and the results were that the differences were very, very minor. Perhaps trivially so.
 

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