Class A vs AB vs D amplifiers

[Ze Frog]

I absolutely love class D amplifier's. One thing I have found is they excel at controlling lower frequencies likely because of really high damping factors. Plus we are at the point now where you can buy a cheaper class D amplifier that gives up very little to the far more expensive class D amplifier's and quality and power that you just won't find in any other class of amplifier at the same price. Add in less electricity used, less heat, lighter and take up less physical space and they really are awesome.

 

[boomtheroom]

What do u think of this comment?

Unlike class-D amplifiers, the AHB2 is noise free over its entire 0.1 Hz to 200 kHz frequency range. Don't settle for the limited performance of class-D amplification.

 

[Basic Channel]

What do u think of this comment?

Unlike class-D amplifiers, the AHB2 is noise free over its entire 0.1 Hz to 200 kHz frequency range. Don't settle for the limited performance of class-D amplification.

Maybe I don't get it (i know little about amps and electronics) but I am 40 and can hear to about 14k. I'm not sure of the value of seeking such a frequency range, never mind noise free. Dolphins hear from about 75hz to 150khz so it's even a bit extreme for them. I totally don't get 0.1hz either, that's like noise anyway, about 15 octaves below 20hz. Anything down there in music would almost definitely be a mistake, giving up precious headroom so you can make the worms think its raining.

 

[Chrispy]

What do u think of this comment?

Unlike class-D amplifiers, the AHB2 is noise free over its entire 0.1 Hz to 200 kHz frequency range. Don't settle for the limited performance of class-D amplification.

My first thought is it it actually free of noise or is it simply exceptionally low? The 200khz part, meh.

 

[rdenney]

What do u think of this comment?

Unlike class-D amplifiers, the AHB2 is noise free over its entire 0.1 Hz to 200 kHz frequency range. Don't settle for the limited performance of class-D amplification.

Have you tested your ability to hear noise over about 15 KHz?

Have you tested recorded music to discover what actual musical content sits above about 15 KHz?

Can your speakers produce any sounds at all above about 20 KHz? Can you hear them? One illuminating test is to play pink noise through an equalizer with no filters in play, and then add a filter at 20 KHz with a 6-dB drop. Hear a difference? Me, neither, as long as the filter slope is steep enough to keep the filter effect above about 15 KHz.

Similar testing below about 20 Hz is also illuminating.

(Warning: Don’t crank up 18-20 KHz signals into your speakers to be loud enough to hear—you’ll fry your tweeters.)

Rick “has conducted these tests” Denney

 

[oleg87]

What do u think of this comment?

Unlike class-D amplifiers, the AHB2 is noise free over its entire 0.1 Hz to 200 kHz frequency range. Don't settle for the limited performance of class-D amplification.

That seems like a very important consideration for audiophile bats.

 

[Album56]

I have very been very lucky to stumble into a combination of amp / speaker that to my ears have transcended my expectations by a margin.
I have a class D Lyngdorf TDAI-1120 streaming amplifier, rated @ 60w into 8 ohms & 120w into 4 ohms, 30 amps peak o/p current.
Originally paired with Dali Rubicon 2 speakers & an old REL sub & after set-up I was extremely pleased with the resulting music, this is my endgame I thought!
But I had a nagging that needed to be resolved.
Back in the 70s I had heard a Quad electrostatic set-up & had never forgotten how sweet that sounded to my young (24) ears.
I needed to hear electrostatic speakers with my amp.
I contacted my local Martin Logan dealer & he suggested I take my amp along & listen to a pair of small EM-ESLs their smallest speaker driven by the TDAI-1120.
To cut the story short I have had the EM-ESLs at home for a year now & with careful positioning, running them full range with the REL just filling the very lowest octave the music is astonishing.
The class D amp able to o/p 30amps peak seems to work beautifully with the electrostatics that go as low as 2 ohms at high frequencies.
The combination is a times astounding.

 

[voodooless]

What do u think of this comment?

Unlike class-D amplifiers, the AHB2 is noise free over its entire 0.1 Hz to 200 kHz frequency range. Don't settle for the limited performance of class-D amplification.

I’m pretty sure that in the audible range, the NCx500 will have a better SNR. The “to 200 kHz” was added in the knowledge that Class D amps are closing in on their switching frequency, like the Purify here:

In any case, these numbers are nowhere near audibility, so rather unimportant as an argument.

 

[Willem]

I think a lot of speakers work well with Class D amps, particularly bookshelf speakers used in a near field configuration. But other speakers sound better with Class A or A/B amps. For example, my Vandersteen 2Ci's.

I am not sure there is a scientific basis for this.

 

[Willem]

I have very been very lucky to stumble into a combination of amp / speaker that to my ears have transcended my expectations by a margin.
I have a class D Lyngdorf TDAI-1120 streaming amplifier, rated @ 60w into 8 ohms & 120w into 4 ohms, 30 amps peak o/p current.
Originally paired with Dali Rubicon 2 speakers & an old REL sub & after set-up I was extremely pleased with the resulting music, this is my endgame I thought!
But I had a nagging that needed to be resolved.
Back in the 70s I had heard a Quad electrostatic set-up & had never forgotten how sweet that sounded to my young (24) ears.
I needed to hear electrostatic speakers with my amp.
I contacted my local Martin Logan dealer & he suggested I take my amp along & listen to a pair of small EM-ESLs their smallest speaker driven by the TDAI-1120.
To cut the story short I have had the EM-ESLs at home for a year now & with careful positioning, running them full range with the REL just filling the very lowest octave the music is astonishing.
The class D amp able to o/p 30amps peak seems to work beautifully with the electrostatics that go as low as 2 ohms at high frequencies.
The combination is a times astounding.

I am a great lover of electrostatics myself as well. My first real speakers bought in 1976 were Quad ESL57s, which I kept for many years, to be replaced by my current Quad 2805s, now also with three subwoofers (plus MSO). In my experience proper dsp room equalization of the subs is crucial, to make sure the room modes excited by the subs do not produce a mismatch with the much cleaner dipole sound of the electrostats. My first amplifier was a Quad 33/303 combo, my current one is an RME ADI-2 and high passed Quad 606-2 combo.

 

[Basic Channel]

I have active speakers, but I'd have thought it you were doing it right, swapping amps should be almost like swapping DACs. Aside from different maximum volumes, I'd be expecting transparent frequency response and only different levels of very low distortion.

 

[Jim Taylor]

It's been my experience trying out different things. If you think there are class D amps out there that will sound better than my Hafler DH120's, let me know!

Given that they are well-designed and operating withing their capabilities, Class D will not sound different from any other well-designed amplifiers that are operating within their capabilities. Class of output bias has nothing to do with it.

This does not in any way imply that all amplifiers sound the same in all situations. Some speakers present a difficult load, and some amplifiers cannot handle that load sufficiently. The common reason is that some designs are made to a price point, but it is also true that some listeners prefer a non-neutral, or deliberately inaccurate sound. The two examples that come to mind are some tube designs and some single-ended solid-state designs. Some manufacturers are willing to pander to the desires for inaccuracies.

Your Haflers do not fall into that category.

The standard method for distinguishing audible differences in electronics is a double-blind test (DBT). The video below gives you the protocols and reasons why they are necessary.

If you were to undergo a DBT, I would expect that any well-designed Class D amplifier of sufficient power would be absolutely indistinguishable compared to your Hafler.

Jim

 

[John_Siau]

What do u think of this comment?

Unlike class-D amplifiers, the AHB2 is noise free over its entire 0.1 Hz to 200 kHz frequency range. Don't settle for the limited performance of class-D amplification.

Class-D out-of-band noise and distortion (above 20 kHz) may interact with the non-linearities of tweeters. This can produce intermodulation distortion (IMD) which can produce noise and distortion at audible frequencies (well below 20 kHz).

Ultrasonic noise and distortion can also create voice coil heating and this can reduce the sensitivity of the tweeter. In severe cases, this could damage a tweeter.

Speakers should not viewed as if they are ideal lowpass filters. Ultrasonic noise and distortion can change the way the speaker responds to in-band music signals.

We cannot simply ignore the noise above 20 kHz and say that it does not matter. We need to learn more about the interaction between the tweeters, the out-of-band distortion, and the music. Unfortunately, this interaction will be different for different tweeter designs.

Class-D amplifiers can provide a cost-effective and compact solution, but they do have performance limitations that should not be ignored.

 

[pma]

Class-D out-of-band noise and distortion (above 20 kHz) may interact with the non-linearities of tweeters. This can produce intermodulation distortion (IMD) which can produce noise and distortion at audible frequencies (well below 20 kHz).

Ultrasonic noise and distortion can also create voice coil heating and this can reduce the sensitivity of the tweeter. In severe cases, this could damage a tweeter.

Was this EVER proven or is it a mere hypothesis? Have you measured how much of the 400kHz switching residuals REALLY finds their path to the voice coil over the system inductances? I did the homework.

 

[John_Siau]

Was this EVER proven or is it a mere hypothesis? Have you measured how much of the 400kHz switching residuals REALLY finds their path to the voice coil over the system inductances? I did the homework.

Any tests results you have would be very relevant to this discussion.

 

[mhardy6647]

Speakers should not viewed as if they are ideal lowpass filters. Ultrasonic noise and distortion can change the way the speaker responds to in-band music signals.

Indeed.
Speakers shouldn't be viewed as ideal anythings!
As a class of things, they're about as nonideal as it gets.
I think that's what keeps this hobby interesting.

 

[RayDunzl]

I wonder how much power the Purify (above) could emit at 500kHz...

 

[MAB]

Any tests results you have would be very relevant to this discussion.

I'm eager to see test results on your claims as well.
All the points seem plausible, they really do. Out of band artifacts may be audible if interacting in a non-linear way, maybe IMD. May even heat up a tweeter.
But most of my audio ideas seem plausible, but not many of them end up actual.

 

[Blumlein 88]

I've seen a write up somewhere on the issue of Class D and tweeters. It may have been an extensive simulation in SPICE, but I seem to recall it went from that to some measurements to confirm the SPICE modeling. Bottom line, don't worry about it as I recall.

 

[Blumlein 88]

Switching Amplifier (Class D) Basics

Just today I read on an internet forum a post by a "hot" new manufacturer of class D amplifiers saying that "the only way to solve the interference problem is to put the amplifier in a completely

www.audioholics.com

This isn't the write up I had in mind, but mentions some of the same things regarding heating tweeters and IMD.

Ran across someone with the idea to feed tube filaments with high frequency class D amps to avoid hum. Seems DC would be better.