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In Reply to: RE: Do all class A amps transition to AB at some point? posted by Prisoners on October 11, 2016 at 08:55:14
I believe there will always be some AB headroom in a *push-pull* class A amp though I'm not certain what determines it. (Single-ended, of course, is class A by definition.)
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SO pure class A means the BIAS voltage is 100% ALL THE TIME.
So if it is a say 50 watt amp, the bias is over 50 watts all the time. A 200 watt class A amp would be a 200watts plus on 100% of the time.
A LOT of heat to get rid of!!!
In fact a class A amp is using the most power AT IDLE. And uses less when it is making music.
With a partial class A, the constant voltage is actually about whatever the A rating is, If the A rating is a moderate percent of the total AB rating. the heat sinks will be sized to fit that A idle wattage use. More so than the actual full AB rating of the amp.
On the other hand... ALL preamps ae usually 100% class A. and plenty of them do not run very warm..
Not quite , they are 25% efficient and correct they can only be full biased into class-a at 8 ohm, well for SS amplfiers.As to multiple outputs , this is a necessity when dealing with SOA , Beta droop , et al. If only doing for 8 ohm load and low power, one could get away with one or 2 pr , Nelson does with his F series of amplfiers. 3Pr is my min for good sonics and SOA , but the amount of necessary class-a is usually determined by speaker load and sensitivity , this is critical , as our ear/ brain calculus will pick up the transition if too soon or too late.
Never heard a small Amp sound better than a big Amp , all things being equal , same for speakers ...
Class A toobs are different , one reason due to the output Transformers ...
Edits: 10/11/16
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