Pure Class A amp help

[JediMa]

I'm tempted to step up with my amp an SMSL H400 to buy a Pure Class A, I've read few reviews and it looks like that for the money Aune S17 evo could be a good deal but I don't know much about Aune and beside this, there are other good options to consider?

 

[Bamboszek]

Unless you need portable space heater there is no other upsides of Class A for audio amplifier in our times.

 

[Roland68]

I'm tempted to step up with my amp an SMSL H400 to buy a Pure Class A, I've read few reviews and it looks like that for the money Aune S17 evo could be a good deal but I don't know much about Aune and beside this, there are other good options to consider?

Make sure you get the current Aune S17 Pro EVO.
Alternatively, there's the new Singxer SA-2. It has higher power output and presumably better test results. It's also a bit cheaper.

There are of course other Class A HPA, but almost all of them only operate in the lower power range in Class A mode and then switch to AB.
Most people don't realize that such small devices simply can't run at higher power levels in Class A without overheating. Furthermore, very loud fans would be necessary to prevent the temperature from exceeding 70°C.
However, even with extremely transparent headphones, I couldn't detect any audible advantage to Class A amplifiers.

 

[DavidMcRoy]

Do I understand correctly that crossover distortion in modern Class AB amplifiers is simply non-existent?

 

[MaxwellsEq]

Do I understand correctly that crossover distortion in modern Class AB amplifiers is simply non-existent?

Crossover distortion is fixed by negative feedback.

No one has ever heard crossover distortion if they listen to a well designed Class B or Class AB amplifier with sufficient and stable negative feedback.

 

[Mnyb]

Crossover distortion is fixed by negative feedback.

No one has ever heard crossover distortion if they listen to a well designed Class B or Class AB amplifier with sufficient and stable negative feedback.

have not muscial fidelity in the past managed to build class-A amps with crossover distorsion , due to them being push pull designs anyway

I have seen some hiraga amp with single ended transistor it had output transformer to remove the DC , it of course had all sorts of distorsion just not crossover distorsion .

 

[MaxwellsEq]

have not muscial fidelity in the past managed to build class-A amps with crossover distorsion , due to them being push pull designs anyway

I have seen some hiraga amp with single ended transistor it had output transformer to remove the DC , it of course had all sorts of distorsion just not crossover distorsion .

Good points!

Obviously there are two approaches to Class A: 1) single-rail, non push-pull where crossover distortion is impossible (but large DC levels need to be blocked) ; 2) dual-rail push-pull where crossover distortion is possible when bias is set low enough for the amplifier to go to AB (but DC is not intrinsically high).

It's always possible to make any amplifier have a sonic character, regardless of Class, by messing up feedback design.

 

[Mnyb]

Some old MF designs where really bad , basically not enough feedback at all. They had an era where they tried to copy tube designs with transistors ? or that's what their marketing said ? confused my at the time .

Later they begun to improve the measured performance some MF products do produce adequate measured performance today .

On topic for an headphone amp this should be to hard ? but why ? i shall not spam the tread further ..

 

[Johnkeizer]

Hi, assuming you just want a headphone amp, not dac, Schiit Audio make the Asgard, now in mk3.
I had the original, got incredibly hot, now have the mk3 and runs much cooler but still apparently class a.
Has no trouble running my Sennheiser 800s and sounds glorious doing it.

 

[dfuller]

Crossover distortion is fixed by negative feedback.

No one has ever heard crossover distortion if they listen to a well designed Class B or Class AB amplifier with sufficient and stable negative feedback.

Not by NFB, but by proper biasing. The entire point of AB amps is that they take a slight hit to efficiency from a class B amp but effectively lack any crossover "step".

You can make class AB amps with no global feedback and they'll still be essentially free of XO distortion.

 

[MaxwellsEq]

Not by NFB, but by proper biasing. The entire point of AB amps is that they take a slight hit to efficiency from a class B amp but effectively lack any crossover "step"

I was perhaps being over-subtle with my language when I replied to @DavidMcRoy in their post #4

Perhaps what I should have said was: 1) crossover artefacts are reduced by bias; 2) crossover distortion (and other forms of distortion) are reduced below audibility by correct deployment of negative feedback.