When someone tells you it's a $40,000 amp, does it sound better?

With great respect, since I'm well-aware of your expertise- is it possible to assign a monetary value to those attributes? 

Yes- and depends very much on who is doing the assigning 😉

Better:

Smoother, more detailed, greater center image palpability. Wider bandwidth, particularly in the bass. Greater speed and so on.

Something to keep in mind is that a $40,000 amp is likely not going to be playing $200 speakers; its likely to be playing on speakers that have a similar price tag. Some speakers with that sort of price really are wider bandwidth and lower distortion. So it may well be that the $40,000 amp sounds better on that account alone...

Yeah that probably relates to higher cost class D amps. But mostly d amps are bargain basement variety and sound pretty bad.

@jumia  That is true of some but not all. I have two customers that were quite surprised by the Nobsound class D amps which are less than $300.00! I’ve not heard one myself. As best I can make out some of these less expensive amps are bass response limited to avoid all their power being gobbled up but otherwise sound pretty decent.

Isn't the harsh reality of class D is that it's to clinical and precise, and harsh. With class AB you get distortion and isn't that what harmonics is all about when you listen to music. It's all about the design and the colorations that are done by the amp designer. Most class D stuff is all about fitting lots of power in a small package.

And class D it's kind of cheap stuff so good luck making class d a preferable way to go

@jumia In a word, no.

I've heard class D amps that are smoother than any class A/AB amplifier. Its easier to design a class D amp that exhibits lower ordered harmonics rather than the higher ordered harmonics which cause harshness and brightness.

This is because with class D its possible to run a lot more feedback than you can with conventional designs! Its a nice side benefit of course that they are less expensive and less heat. There's a problem with feedback in conventional designs; not enough of it results in the amplifier's presentation being harsher and brighter due to unmasked higher ordered harmonics generated by the feedback itself. But if you can run enough feedback, it can clean up the mess it otherwise causes.

So at least with the class D amps with which I"m most familiar, they sound as smooth and sweet in the mids and highs like the best tube amps, but with more detail (easier to hear into the rear of the soundstage) than conventional amps.

what about reference sampling clock purity, do we need $20k World clock device for sampling analog input signal to match class-D amp with the rest of audiophile setup?

@westcoastaudiophile 

If you mean the 'clock' for the encoding scheme of the amplifier, the answer depends on how the amp runs. If the amp is zero feedback it will be found that the triangle wave generator has to be really stable in order to prevent noise (hiss) being generated at the output. 

But if the amp is self-oscillating, the amp is immune to minor drift in the switching frequency.

I wish you (really) good luck matching tube amp with D-class Amp! 

Thanks. We think we've succeeded in that- we've been making tube amps for nearly 50 years at this point.

I’ve seen any king of while spectrum noise in different D class amps.. never sine wave! higher freq. though! higher switching freq. amps theoretically should be easier to filter noise out, but again, switching frequency generator has the same reference clock generator issues as any DAC, such as phase noise etc., thus can be heard. 

@westcoastaudiophile If the output filter is doing its job, all you'll see at the output of a class D in terms of noise will be the sine wave residual that is at the switching frequency of the amp. That typically might be from 500KHz (near the bottom of the AM radio band) up to about 800KHz.

Honestly no-one can hear that.

What one might be able to hear is knock-on effects from other equipment if the amplifier has spurious parasitics that are messing with that other equipment- RFI can do messy things with audio.

But to be fair, lots of tube amps can do this too, through the swept resonance that can occur between the power transformer and the rectifiers installed.

We spent a lot of time chasing parasitics in our design. When it was finally ready, when we did the testing of our amp it was the bridge rectifier in the power supply that was making the noise, which we fixed. That is why I said a class D amp can have less spurious noise than a tube amp- whether in the speaker on radiated from the amp through the air or thru the AC power. 

not really, please try to hookup the oscilloscope to the class-D amp output while driving speakers at moderate power, and check residual noise..

@westcoastaudiophile  Are you referring to the 'residual',  a sine wave that occurs at the switching frequency of a properly designed class D amplifier?

If not ('residual noise' can be interpreted several ways), when you connect the 'scope to our class D amp at least, its clearly quieter than any solid state or tube amp I've tested. Of course, there is the residual, but its of no consequence as soon as it encounters the inductance of a tweeter.

How can this be when the turning on and off of output transistors at a rapid rate in Class D amplifiers produces high frequency noise which must be filtered out? There is no such thing as instantaneous switching.

I tried a Class D amplifier the last time my Colosseum was in for repairs and I hated the thing. It sounded harsh and gritty to me. Granted, it was a $1-2k Class D amplifier. I sold the Glass D amplifier as soon as my Colosseum came back to me.

@larrykell I get that- there is tremendous variance in the sound and technology of class D amps- if you heard the wrong one it can be a big turn off!

How the amp can be immune to crossover distortion has to do with how the audio signal is extracted from the switching of the amp. The output devices turn on and off for differing amounts of time depending on the slope (how steep it is, whether its going up or down) of the incoming audio signal.

This type of analog encoding is called Pulse Width Modulation.

When the switching frequency is filtered out, the audio signal is what remains; there’s no way to generate crossover distortion, inherent in the design. This is a considerably different approach as opposed to traditional Push Pull amplifiers where the output devices have to follow the signal (which is why they can be prone to this problem) in order for it to be amplified.

(Apparently it is possible to build a class D amp that has no output filter; if such an amp were built it could have a problem with crossover distortion. But I know of no such commercially available amp- all I’ve ever seen use output filters.)

Regarding noise, if the class D is designed properly the amount of noise it makes on account of its switching can be less than many tube or solid state amplifiers. They can also have considerably less noise floor in the loudspeakers, making them suitable for driving horn speakers.

There can be no crossover distortion because the transistors never turn off.

@larrykell It might interest you to know that most class D amps are inherently incapable of crossover distortion.

On the other hand, with an easier speaker load sans passive cross-overs, not least with speakers more efficient, you have a much better outset with less power needed to accommodate topologically more simple and cheaper amps, while maintaining the same (or more) headroom/SPL envelope. To me at least, that's the better hand to be dealt, while saving you a lot of money. 

The other advantage of easier to drive speakers is the amplifier, regardless of technology, will make less distortion. That will result in a smoother and more transparent presentation, since a lot of that added distortion will be higher ordered harmonics to which the ear is keenly sensitive, and otherwise distortion tends to obscure detail.

Veblen Effect

Abnormal market behavior where consumers purchase the higher-priced goods whereas similar low-priced (but not identical) substitutes are available. It is caused either by the belief that higher price means higher quality, or by the desire for conspicuous consumption (to be seen as buying an expensive, prestige item). Named after its discoverer, the US social-critic Thorstein Bunde Veblen (1857-1929).

https://www.monash.edu/business/marketing/marketing-dictionary/v/veblen-effect

One example I've seen given to showcase this is college tuition. Colleges found that if they decrease tuition enrollment goes down and goes up when they increase it.

Another example is Campagnolo, a well-known bicycle parts brand. Rather than price according to a formula, they price according to what the market will bear.