Audiophiles, generally don't like class D amps!

[JanesJr1]

There have been a number of double blind amplifier comparisons done, which included class D and Class AB amps.... the conclusion of which was that "all amplifiers sound alike".

The proviso to that being, they sound alike as long as they are running within their specified performance envelope... and that we are comparing "quality" components, and not the bottom of the market cheapies...

Given proper DBT rigour - proper precise output level matching, choice of speakers that do not strain any of the amps (put them outside their specified performance envelope), etc...
They ALL sounded the same.

Conclusion being: Topology of the amp is not relevant, implementation is everything. And choosing between topologies is ultimately not about audible difference at all.

It may be to do with specific speakers that one amp drives better than another
It may be related to long term maintainability / repairability (class D's mostly score poorly here!)
It may be sheer "Bling" - eg: that McIntosh amp looks great in my rack...

But you are unlikely to hear a difference between a Benchmark AHB2 and a Purify or Hypex amp in a properly constituted comparison test.

Although you don't mention the specific studies, I appreciate your concise reply, thank you! I'll bet it's somewhere on ASR and keep an eye peeled for it.

 

[SIY]

It's important to remember the distinction between slew rate and bandwidth.

It's important to realize that there's no engineered amp made in the past half century that has slewing distortion. The term just seems to hang on, usually well misunderstood, in the cobwebbed corners of the faith-based audio niche.

 

[Philbo King]

Ok, I know I shouldn't, but I've been reading feed back on an audiophile site on experiences with various Class D based amplifiers. (Purifi, Ncore, and a couple of others less well known to me)

I expected a bit of bias towards older technologies, but it was close to 100% against class D.

What is it that these people are experiencing? They can't all be wrong can they?

• Is it that they miss the distortion/colour from their class AB amps?
• Has this become normalized/expected?
• Have they been programmed to dislike class D because everyone says it isn't as good, i.e bias?
• Is there actually something else at play here?

Everything I hold as important in audio and electronics in general is about achieving the required performance/specs, 'the truth', or at least as close as we can economically get, am i wrong, because these people would appear to say so.

Back in our day, we only had vacuum tubes. And we liked it! None of those newfangled transistors! None of those integrated circuits! None of those class D,E,H amps! They're all works of Satan!

<snicker>

 

[theREALdotnet]

Back in our day, we only had vacuum tubes.

You had vacuum tubes? The decadence! We wouldn’t afford vacuum, our tubes weren’t even closed at the top!

 

[DonH56]

I had vacuum tubes. Couldn't afford air.

 

[Blumlein 88]

Indeed about slew rate and bandwidth. A larger signal at a low frequency can have the same slew rate as a smaller signal at a higher frequency. Slew rate and frequency are not tied solidly together.

 

[Galliardist]

Back in our day, we only had vacuum tubes. And we liked it! None of those newfangled transistors! None of those integrated circuits! None of those class D,E,H amps! They're all works of Satan!

<snicker>

I know this game.
"Right. Back in our day, we had to read the soot patterns on the piece of paper and guess what had been recorded from it. And it STILL sounded better than class D".

Listen to World's Oldest Recording | HISTORY Channel

On April 9, 1860, 17 years before Thomas Edison invented the phonograph, Parisian inventor Edouard-Leon Scott de Martinville made a recording on a

www.history.com

 

[Bjorn]

In the last year, I’ve moved from AB to class D. The class D pretty much transformed my speakers. Bass and clarity significantly improved. But, I do miss one aspect of the AB, (which I’ve not yet experienced with my class D): voices sounded so nice on my old amps. They somehow just felt more relaxing on the AB.

Can anyone explain this? Is it simply due to more harmonics/distoritions with class AB, which I subjectively perceive as ‘more relaxing’? I have now tested a number of both AB and class D, and my impression still remains. I have nothing against neither AB or class D, i like them both.

It's very likely related to distortion. If an AB amplifier has similar low distortion to your class D amp, the sound will be the same. We see that when people test the very best measurable class AB vs the best of class D. They generally experience the sound to be more or less identical.

Here's an example of a class D design that will not sound transparent and a good number of audiophiles find it to sound very "musical":

Spec RPA-W7EX Real-Sound power amplifier Measurements

Sidebar 3: Measurements When I unpacked the Spec amplifier for testing, I was at first confused: Although Ken Micallef was supposed to have reviewed Spec's RPA-W7EX, a label on the amplifier's rear panel identified it as an "RPA-W5ST." It turned out that this very early export sample of the...

www.stereophile.com

 

[Vacceo]

My system is balanced enough that it can tolerate all music. But many systems and living rooms aren't there, and I understand well why some will use electronics with audible distortion to make it more pleasant and enjoyable.

Which is a very unreliable method compared to equalization.

 

[antcollinet]

The speed that an amplifier can react and follow that dynamic of an audio signal is finite.
If it was infinite then yes, the THD and IMD would be equal and steady state signal would describe the transitional state perfect.
But real life amp does not have infinite bandwidth and zero phase distortion, or delay in that bandwidth. Real amps have limited slew rates and finite bandwidth.
Those play into... how well it will follow a transient signal. Step impulse response is one of the tests that tries to measure this, but not only.
Amplifier transfer function and poles compensation is something that is not needed to deal with, if one just plays a 1000Hz sinusoid. So, the steady state measurements are not everything and all.

A system may have low distortion for a steady-state signal, but not on sudden transients. In amplifiers, this problem can be traced to power supplies in some instances, to insufficient high-frequency performance or to excessive negative feedback. Class D has it's own issues related to how the output error is integrated.
Related measurements are slew rate and rise time. Distortion in transient response can be hard to measure. Many otherwise good power amplifier designs have been found to have inadequate slew rates, by modern standards.

Distortion is a result of non linearity in the amplification. Not of bandwidth.

(Speed/slew rate are easily defined by (full power) bandwidth.)

 

[nygafre]

It's very likely related to distortion. If an AB amplifier has similar low distortion to your class D amp, the sound will be the same. We see that when people test the very best measurable class AB vs the best of class D. They generally experience the sound to be more or less identical.

Here's an example of a class D design that will not sound transparent and a good number of audiophiles find it to sound very "musical":

Spec RPA-W7EX Real-Sound power amplifier Measurements

Sidebar 3: Measurements When I unpacked the Spec amplifier for testing, I was at first confused: Although Ken Micallef was supposed to have reviewed Spec's RPA-W7EX, a label on the amplifier's rear panel identified it as an "RPA-W5ST." It turned out that this very early export sample of the...

www.stereophile.com

Thank’s for the reply ! interesting reading

 

[dlaloum]

Although you don't mention the specific studies, I appreciate your concise reply, thank you! I'll bet it's somewhere on ASR and keep an eye peeled for it.

Theres a thread around here somewhere attempting to collate double blind tests...

 

[Mnyb]

It's important to remember the distinction between slew rate and bandwidth.

It's important to realize that there's no engineered amp made in the past half century that has slewing distortion. The term just seems to hang on, usually well misunderstood, in the cobwebbed corners of the faith-based audio niche.

+1
yes this caveat engineered . in the cobwebbed corners of the faith-based audio niche. You will probably find slew limited designs (that's usually only one of their issues )
These faith based design usually "sounds" incredible for unknown if not magical reasons

I mistake in our reasoning here at ASR is that we expect engineered solutions , why not ? if the correct way to do stuff has been known for 50 years and are in textbooks it's a very reasonable stance is it not ?

Faith based audio does not operate in this way . we can probably expect every solved problem to reemerge to bite us in the a*s when least expected.
Like when nutcases removed the filters from DAC's and made that a fad ?

 

[nowonas]

+1
yes this caveat engineered . in the cobwebbed corners of the faith-based audio niche. You will probably find slew limited designs (that's usually only one of their issues )
These faith based design usually "sounds" incredible for unknown if not magical reasons

I mistake in our reasoning here at ASR is that we expect engineered solutions , why not ? if the correct way to do stuff has been known for 50 years and are in textbooks it's a very reasonable stance is it not ?

Faith based audio does not operate in this way . we can probably expect every solved problem to reemerge to bite us in the a*s when least expected.
Like when nutcases removed the filters from DAC's and made that a fad ?

Yes, I agree that we should expect engineered solutions as you say. However, since this is a discussion on class D amplifiers, I think your comment can be a bit confusing. The concept of slew rate does not make sense for class D amplifiers ( or even for modern linear audio amplifiers at all.). So if you are expecting that a well engineered class D has a high slew rate because it has been so for 50 years and in text-books (as you state), you are expecting something that does not exist. In 2023 slew rates are mostly operational-amplifier related, where it still makes a lot of sense, particularly for non-audio applications, where waveforms can have sharp edges. Audio people started to consider slew rates many years ago in the context of linear amplifiers that could not produce full output up to 20Khz, (or whatever upper frequency was required in each application, not only audio!). This was because some internal stage would clip before delivering enough current to charge the input capacitance of the next stage fast enough. This results in "triangulation" of the output waveform (when maximum slope is reached).

Nothing of this exists on class D, there are no linear power amplification stages and no triangulation is possible (at least not unless the designer did something really wrong, like using a too big output capacitance with a too low current limit, so unlikely).

 

[Ricardus]

Keep reading; I have read it here many, many, many times. The emphasis is on transducers, somewhat less so on amps, and least on DAC's. The limitation is that ASR, by nature of its volunteerism and mission, is focused primarily on measurements of donated or loaned equipment via Amir and a few others, rather than on expensive research projects. By-the-book controlled listening tests are occasionally done by members but much more often are incidentally reported here second hand by those members who stay in touch with industry and academic projects.

Link me up.

 

[wjp007]

PCM signals don't directly encode PW so you'd still have a conversion step either way. Even DSD doesn't work using PWM, although it's similar.

But PCM can be easily converted to PWM in the digital domain. That's my point, why go through an analog conversion?

 

[mhardy6647]

I had vacuum tubes. Couldn't afford air.

Kids these days with their danged highfalutin' tetrodes and pentodes!
Heck, when I was a lad, we didn't even have triodes, and only the rich could afford a diode.
We made due with monodes, we did!

 

[atmasphere]

A system may have low distortion for a steady-state signal, but not on sudden transients. In amplifiers, this problem can be traced to power supplies in some instances, to insufficient high-frequency performance or to excessive negative feedback.

Uh, Yikes.
Or it might be traced to a part of the amplifier outside the feedback loop, such as the base of an input transistor.

If the feedback loop is properly designed, quite a lot of feedback can be used with only benefits. 'Excessive feedback' isn't so much a thing as 'poorly applied feedback'.

 

[fpitas]

Your understanding of amplification is certainly novel.

Very tactful!

 

[fpitas]

Kids these days with their danged highfalutin' tetrodes and pentodes!
Heck, when I was a lad, we didn't even have triodes, and only the rich could afford a diode.
We made due with monodes, we did!

I had tunnel monodes, before they were popular