Class AB Amp

246

03:11:08

56W from 190W(peak). This is probably the simplest amplifier without compromising power or soumd quality. Although the first stage is purely class A and would probably give very nice results the second stage is a push pull which will  cause some crossover distortion (more or less depending on the biasing techniques) and would somewhat deteriorate the sound quality. Nevertheless this is the easiest you'll get at 64W with decent quality. And yes there is no such thing as a free lunch. With this amp the cost is power. A lot of continuous power dissipation will occur in the class A stage thus lowering the efficiency levels. But at least the class B amp somewhat compensates for the utterly inefficient class A stage.

published 11 years ago

faceblast

11 years ago

might have a go at it, which transistor do I use to maintain 500hfe at that power

Secuture

11 years ago

Did u know that pure class A power amplifier (nomatter is it complementary or single stage) with transformer as output coupler has max efficiency of 50% compared to max capacitive coupled of 25%??? So theoretically in ideal case from 200w a 100w is already available to load and still maintain class A operation . So in real case a 48%-49% is to obtain easily.

thebugger

11 years ago

You can make it using a darlington configuration. You just have to select the 2 transistors with the appropriate hfe. Like the first transistor should be low or medium power with a 50hfe like 2t6551 or other (use a multimeter to make sure of the hfe for both transistors cuz I see its quite dependant) and the second one could be a 2n3055 or equivalent with a 10hfe. Or you could just scout the net for a readily encased Darlington transistors. There are a lot of them I even used to have some but I cant remember their name.

Secuture

11 years ago

Best audio transformers u can ever buy today http://www.lundahl.se/ if u plan to build class A amp of ur life this one i will personally recommends. Best hi-end amplifiers are mostly equiped with this company inductors and they offer any u want : interstage , line in/out, regulated ripple filter chokes, output speaker transformers, mains power transformers etc,etc and all design exclusively to be used in best audio equipment. Take a look

thebugger

11 years ago

Yeah I know inductive coupling doubles the efficiency levels but what traf should be used?

Secuture

11 years ago

U should use a Proper!! One!! Lol XD any other wil not perform very good.

thebugger

11 years ago

What does a proper mean? Primary? Secondary? Inductance?

thebugger

11 years ago

50% is a good efficiency level for a class A amp (which I'd always prefer nevertheless their inefficiency levels,they always compensate with the best results) so id really like a good 5 or 10W design for home use if someone has aby ideas. Man EC really needs a forum.

dkobe

11 years ago

Interesting amplifier. I was able to increase the input level to 800mV before it clipped symetrically. The output signal peak to peak reached 35.5Vpp. 35.5 squared times 8x4 ohms only yields 39.4 Watts rms. Times 1.414 = 56 Watts peak power, not 190. As u stated, the class A voltage amplifier runs quit hot...about 9.6 Watts. This would need to be a To-220 (or similar style) with a Large heatsink. (R u sure the output is class B? :-)

dkobe

11 years ago

Opps, I meant 35.5Vpp squared Divided by 8x4 ohms. My apologies.

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