A push-pull tube design and Single-ended class A designs


Hello,

Between a push-pull tube design and Single-ended class A designs amp, is Single-ened class A better in sound quality, why?

Regards,
Eddy
eddy1
Its not that simple!!

SETs work really well if you have a speaker efficient enough to really take advantage of their strengths. If you don't, you are wasting the money invested in the amp! SETs should be used such that only about 20% of their total power is invoked at any time during your listening session. If you use more power than that, the distortion gets high enough that the amp will be pretty distorted on musical transients. The kind of distortion present (higher ordered harmonics) is used by the human ear brain system to calculate the volume or loudness of the sound (Loudness Cue). So the result is that the loudness cues will ride on the transients, causing the amp to sound very 'dynamic'. This is why you hear tales about how SETs are so dynamic for their otherwise low power. Its distortion masquerading as dynamics.

Essentially when describing dynamics, you can replace the word with 'distortion' and not change the meaning of the conversation.

OTOH, at lower power levels the distortion becomes unmeasurable, quite unlike that of most push-pull amps. This is the source of that 'inner detail' for which SETs are so lauded.

Push-pull amps do better at higher power levels (having less distortion), and so sound smoother when you push the system harder. In addition, they often have more power and wider bandwidth, which means you can run less efficient speakers that might have more bass response (typically the kind of speakers you need to work with 90% of all SETs need to be over 100db 1 watt/1 meter for best results- this means they won't be playing that bottom octave and may be missing some of the octave above that as well).

We've not described the effects of loop feedback, which is a conversation on its own, but many P-P amps have it while most SETs do not. Feedback can cause the amp to sound brighter due to bifurcation of existing distortion into higher orders, which the ear treats simultaneously as brightness and harshness.

If the Push-Pull amp is designed properly (no feedback and no separate phase splitter circuit), the distortion will also decrease with power to unmeasurable, but IME these types of Push-Pull amps are rare. However if that quality is present its sort of like get your cake and eat it too- you have the advantages of SET (good lower level detail) without the power or bandwidth limitations. 
As with most things it's not the topology it's who's implementing it. There are good and bad examples of both types of amps.
Eddy,
Which is better will depend overwhelmingly on your chosen speakers, it really comes down to that. I've been using a 300b SET amplifier for over 6 years and there's no going back. Prior to this I'd use various push pull amplifiers for about 15 years. I've heard many different push pull amplifiers and like everything else there is a hierarchy of performance. 

You'll have to get a SET built  to a high quality standard (output transformers and power supply ) with quality parts. If you couple a SET of this caliber and match it to an appropriate speaker, I believe that you'll be very happy.  I have more purity of sound and naturalness of music presentation than ever before. That's just my experience,superior natural character. 

There's no doubt that you can also develop a terrific sounding system utilizing push pull amplifiers, again it depends on speaker choice and your individual taste and objectives. 
Goodluck, 
Charles,