Class D Technology

So based on a combo of facts and experience I still see it as one of theoretical things that exist but do not add up to much if anything in practice for most.

Are you going to be producing an amplifier anytime soon?

If an amp cuts off at 20KHz then expect phase shift artifacts down to 2KHz. If an amp cuts off at 60KHz then its 6KHz. If the cutoff has a steep slope the artifacts can be more severe. The trick, if you can't get bandwidth the way you want, is to not have a severe rolloff.

You'd think this stuff is inaudible but it isn't. Many factors add up to how a given amp sounds and its plain foolish to attempt to focus on any one factor by holding it above others **or** below. They **all** affect the result.

So you are right in a sense. But I'll give you an example of how phase shift can manifest. Years ago a dealer brought an MFA Magus preamp to me with the complaint that it was really bright in the phono section. In fact I had heard this problem in the preamp myself. I put it on the bench and  found that in the RIAA equalization there was a circuit that caused the equalization to go to flat at 50KHz. This is a ways above human hearing. Normally the RIAA curve would be rolling off at 6db per octave.

So I took the circuit out, thus restoring the RIAA curve (FWIW the RIAA  did not spec the curve past 20KHz but it usually designers assume that it will continue with its 6db per octave rolloff as frequency goes up). The **very audible** brightness was eliminated! The dealer was thrilled, and MFA changed their production so that this circuit was omitted. Apparently they didn't like the brightness either, but had not made the phase shift connection. They said it was there to "improve square wave response". I'm sure it did that!

If your amp does not have lot of bandwidth then you are in the same boat as a lot of SET owners and they seem to like their amps just fine. The fact is that its not the most important thing in the world. But don't confuse that with it not being audible at all! In a class D amp, most of the artifact that its going to have is coming from the input circuit and in that regard whatever amplification it has (probably an opamp) which imposes its own signature. That's a lot better than the signature that many transistor amps impose; opamps if treated right can be pretty musical. If the bandwidth is limited then the amp might not seem very bright and a lot of audiophiles (myself amongst them) cringe when things get too bright. You like your amp a lot so if your hearing isn't too off than I have to assume that the designer chose a reasonable set of compromises in the design. I guarantee though that the designer would prefer to work with greater bandwidth if possible. When they come out with the latest greatest replacement for your amp (which will happen sooner or later), take a look at the bandwidth spec and see if they didn't improve on it. 

Are you going to be producing an amplifier anytime soon?

Nope. Not my lot. I’m just a critical listener reporting what I hear and trying to understand why.

I already have two generations of Bel canto Class D amps. I have yet to hear any hint of brightness ever with the newer one. Even with Dynaudio Contour monitors known to lean that way with the wrong amp. It is an all in one integrated the C5i so less to get wrong or right when matching . In fact one of the reasons I bought it was to be able to compare and contrast with what I had. And guess what, better bandwidth and improvements in general with a newer and still evolving technology is exactly the thing that leads me to keep testing the waters.

As I said I do not doubt the relevance of bandwidth in theory, only is it an issue of enough magnitude in practice that most people would care these days when things are done well otherwise.

Some people report brightness in some Class D amps. Same true with other SS amps. Probably even with tube amps to a lesser degree. But I am not hearing it at all ever, in fact less than ever, with my latest and greatest Class D amp. So I do not find the fears bandied about with the technology in general to be warranted at all in practice.

Nor am I saying all Class D amps perform equally well either. Only the ones I own and know well for sure. That just proves to me it can be done now and today. I am not alone there I would say. YM always varies.

Its nice to hear a maker of tube amps and another of passive pre-amps gives the competing technology some credit. Its only fair to point out where the achilles heels lie. Every product has one. All good information for the educated consumer to mull over when making a decision.

Here is part of Lamm Industries ML3 Signature amplifier by Michael Fremer in 9/2013 Stereophile.

The ML3s produced the most glorious, palpable, airy, detailed midrange I’ve ever heard from reproduced music. That part is easy. They pushed that performance envelope without going all greasy and congealed over time, as some tube amps do after the initial appeal of warmth wears off.

The ML3’s standout features were its natural re-creation of instrumental attacks, generous sustain, and lifelike decay—all as close to live as I’ve heard, if nowhere near the real thing. It was quiet, fast, detailed, dynamic without reservation, transparent, airy, and extended on top. No sharp edges unless the recording had them, and no boredom-inducing global softening. The pair of them produced an enormous sense of space when that was appropriate, and, within that space, images of exceptional delicacy, three-dimensionality, and body.

It should be good for $140k/pair. This amplifier has measured -3dB bandwidth at about 50kHz - which is 15kHz less than my class D amp, that supposed to suffer from wrong harmonics summing. Please notice words "airy, and extended on top". Imaging also did not suffer.

He also stated:

Most startling, though, was the ML3s' effortlessly clean and airy high-frequency extension. 

Full text:  http://www.stereophile.com/content/lamm-industries-ml3-signature-monoblock-power-amplifier#HxPd7KZt3...

I will try Class "D" when it get's as common as "bacon and eggs". In the meantime I will maintain my staunch prejudice against Class "D".

Did you know that the vast majority of people who hate "Black" people have never seen one up close and personal. If that can be accepted, I'm sure my stance on Class "D" amps can be accepted; in both cases there is no logical or rational reason for such a stance.

But seriously, I have already "verified" that computer sonics, and analog sonics, are impossible to tell apart, if the computer is done right; evidently it depends on the level of switching; but there are many indistinguishable differences that "audiophiles" claim to hear; such as six 9's copper; 99.9999% pure.

While there is a difference in the quality of interconnects, and it is due to the composition of the wire, the composite of silver plus copper for example, but that also has a scientific variable in ohms. When so many minute differences are carried to such great extremes, accompanied by extreme prices; without any scientific merit, I for one am quite dubious, as in the case of interconnects. I strongly suspect that almost any difference is interpreted as better; how else could you explain a 1K price for a 6 foot piece of copper wire?

Some of these differences are at a "subconscious" level; tube, and solid state for example. I think SS is best for rock, and tube best for "smooth sounds and female vocals"; but I am speaking of a tube pre and SS amp, where the difference is even smaller; when both are SS, then it's audibly obvious.

There are many dubious things on this forum, that I "strongly" suspect are no more than opinion, but "placebos" are good for one's mental health; that is, if the health of one's bank account can accommodate this feel good luxury.

I suspect I have become an "Audiophile"; it snuck upon me when I wasn't looking.