Class A vs AB vs D amplifiers

[MAB]

This is the impedance formula, not what you write

Yes, you are correct. Today I feel stupid.
Did you get the point that the impedance is really high and dominated by the voice coil inductance at hundreds of kHz?

 

[pma]

At 400kHz switching frequency the voice coil impedance is almost completely inductive, so the 2*pi*f*L simplification is completely fine. Just consider it is a reactance.

 

[boomtheroom]

So..... all I get form this is An amp like the nad m23 class d will sound like perfection.

 

[SIY]

So..... all I get form this is An amp like the nad m23 class d will sound like perfection.

Within their drive limits, pretty much all engineered amps do, yes.

 

[pma]

Under “usual” listening conditions with “usual” speakers, yes.

 

[SSS]

Linear Class-A (without any distortion) is by design the best because tiny signals will be kept as they are. The first watt idea is basically right to my knowledge. Without bass in the music (voice, acoutic guitar and such) the needed power for the speakers is low.

 

[goryu]

Linear Class-A (without any distortion) is by design the best because tiny signals will be kept as they are. The first watt idea is basically right to my knowledge. Without bass in the music (voice, acoutic guitar and such) the needed power for the speakers is low.

Which class-A amps are "without any distortion"?

 

[Vacceo]

Linear Class-A (without any distortion) is by design the best because tiny signals will be kept as they are. The first watt idea is basically right to my knowledge. Without bass in the music (voice, acoutic guitar and such) the needed power for the speakers is low.

In what way is that different to a Hypex or Purifi model with no audible distortion?

 

[MAB]

Linear Class-A (without any distortion) is by design the best because tiny signals will be kept as they are. The first watt idea is basically right to my knowledge. Without bass in the music (voice, acoutic guitar and such) the needed power for the speakers is low.

Are you sure about 'without any distortion'?
Even the companies that make these Class A amps don't claim there is zero distortion. They just claim that one type of distortion is reduced.

None of this has prevented me from owning Class A amplifiers over the years (I still own), I am just quite realistic about what they are capable of.

 

[SSS]

Of course in real world nothing is absolutely perfect. So also Class-A amplifiers since there is always a little deviation from straight line amplification factor.
Class-D power amps have raising THD when the signal level declines which all the ASR tests show. OK, these distortions may not be heard I agree. But for me this was not the question. In Class-A there are no switching artefacts like at Class-D.

 

[goryu]

Of course in real world nothing is absolutely perfect. So also Class-A amplifiers since there is always a little deviation from straight line amplification factor.
Class-D power amps have raising THD when the signal level declines which all the ASR tests show. OK, these distortions may not be heard I agree. But for me this was not the question. In Class-A there are no switching artefacts like at Class-D.

Can you name one class a amp on the market that compares favorably objectively with either Purifi or Hypex amps?

 

[SSS]

Can you name one class a amp on the market that compares favorably objectively with either Purifi or Hypex amps?

NO. Since as I said there is no perfect amp available. Each class has its benefits but also drawbacks. But one idea, why there are at least to my knowledge no preamplifiers in Class-D technology if this type is called better than A or AB.

 

[goryu]

NO. Since as I said there is no perfect amp available. Each class has its benefits but also drawbacks. But one idea, why there are at least to my knowledge no preamplifiers in Class-D technology if this type is called better than A or AB.

And yet you said this:

"Linear Class-A (without any distortion) is by design the best because tiny signals will be kept as they are."

So you can't name a single class a amp that compares favorably objectively with the Hypex or Purifi amps yet class a is by design "the best because signals are kept as they are"....You aren't making any sense....

 

[tomtoo]

Long story short, yes. So-so class-D designs have load dependence and don't always have flat frequency response. So that could easily lead someone to call it "grainy" if the treble was going all over the place in an old, cheap design.


Modern high-end Class D amps have as good or better noise, distortion, and power than most of the Class A or A/B amps out there, and especially when you compare by price.


Simply put, today's good Class D amps are just plain good, in all of those aspects.

To put it another way - many of the Class Ds you can get today (a fun example is the Fosi V3 monoblock) have ideal frequency response in the audible band, inaudible noise, and inaudible distortion. Once you check those boxes, there is no other way for the amp to mess up your sound.

So, yes they've done it, they've made Class D as good as anything else.

Better, you get much more ummmppfff for the da same money. You not only have great sound but also more ummppff.

Sometimes it gets boring. YES a good class d amp is just better than the oldies at the same price.

 

[Doodski]

Better, you get much more ummmppfff for the da same money. You not only have great sound but also more ummppff.

Wayyy more ummmpF!

 

[SSS]

And yet you said this:

"Linear Class-A (without any distortion) is by design the best because tiny signals will be kept as they are."

So you can't name a single class a amp that compares favorably objectively with the Hypex or Purifi amps yet class a is by design "the best because signals are kept as they are"....You aren't making any sense....

My statement was a more theoretical one. If the amplification factor is kept linear over level so class-A has no switchower effects nor any artefacts from switched transistors like at class-D or at class AB where there is a transient region. Since I have no access to high-priced class-A power amps I can't compare or judge them. There are technical books available covering the amplifier classes with their goods and bads. It is true on the other hand when power is needed at relatively low cost then a Hypex and a Purife module may serve well.

 

[Doodski]

My statement was a more theoretical one. If the amplification factor is kept linear over level so class-A has no switchower effects nor any artefacts from switched transistors like at class-D or at class AB where there is a transient region. Since I have no access to high-priced class-A power amps I can't compare or judge them. There are technical books available covering the amplifier classes with their goods and bads. It is true on the other hand when power is needed at relatively low cost then a Hypex and a Purife module may serve well.

I have metered a ton of class AB amps and I magnified the waveform with a dual time base so that I could really see if there was even a hint of crossover distortion and all of them where clean and no switching distortion at any volume settings. I have owned a real class A USA made power amp that was linear down to 2 Ohms. It was a nice amp, was beautiful inside and outside and I enjoyed it very much. It was colored. It sounded like a soft sounding tube amp. Not because it is class A but because the designer apparently introduced coloration in the final result. If it was a pure class A with no coloration it would not sound different.

 

[SSS]

I have metered a ton of class AB amps and I magnified the waveform with a dual time base so that I could really see if there was even a hint of crossover distortion and all of them where clean and no switching distortion at any volume settings. I have owned a real class A USA made power amp that was linear down to 2 Ohms. It was a nice amp, was beautiful inside and outside and I enjoyed it very much. It was colored. It sounded like a soft sounding tube amp. Not because it is class A but because the designer apparently introduced coloration in the final result. If it was a pure class A with no coloration it would not sound different.

I admit that with a regular oscilloscope you may not have seen crossover signal degrading. But an oscilloscope is not able to display tiny distortions in the waveform what we talk about. Digital scopes have a resolution of 8 bit data witdh, very good ones 12 bit. There may today be now ones with more than 12 bit, I did not check Tektronix, (HP) Keysight and Rohde&Schwarz or LeCroy products for this.

 

[Doodski]

I admit that with a regular oscilloscope you may not have seen crossover signal degrading. But a oscilloscope is not able to display tiny distortions in the waveform what we talk about. Digital scopes have a resolution of 8 bit data witdh, very good ones 12 bit. There may today be now ones with more than 12 bit, I did not check Tektronix, HP and Rohde&Schwarz or LeCroy products for this.

I used a analogue Tektronix 7603 Lab Scope with dual time base and 150MHz vertical amps. The dual time base realllly gets the magnification of the waveform. Can see everything with a scope of this caliber.

 

[whit]

Would it be generally accurate to say that there's more difference between amps due to the rest of the implementation, rather than whether the core technology is B or D? I also suspect much of what we hear is beyond the range of what we have statistical instruments for, otherwise there's no sense in how amps sound different despite having equally good stats and being run within their power ranges.