First I have to say thanks for this brilliant site , I love it .
Anyway I've been experimenting with John Lindsay Hoods "69" Class A circuit .
First I tried it without the bootstrap capacitor on tr2 load resistors .
Pure Class A .
Sounds great at low level but unacceptable distortion at hi levels.
Next tried led / transistor constant current source for tr2 . Wow more punchy and aggressive sound , no didn't like that sound so tried adding a class A phase splitter / current driver . I see this current splitter idea in his original Wireless World 69 article . It makes sense to me , tr2 is now vas , tr3 is current driver / phase splitter . tr4 / tr5 outputs are biased in pure class A . I've built this circuit and it makes sweet music . Under simulation optimum bias current is 0.8 amps for ten watts output into 8 ohms . My question is this , do you guys like the circuit ? how would you improve it ?
Anyway I've been experimenting with John Lindsay Hoods "69" Class A circuit .
First I tried it without the bootstrap capacitor on tr2 load resistors .
Pure Class A .
Sounds great at low level but unacceptable distortion at hi levels.
Next tried led / transistor constant current source for tr2 . Wow more punchy and aggressive sound , no didn't like that sound so tried adding a class A phase splitter / current driver . I see this current splitter idea in his original Wireless World 69 article . It makes sense to me , tr2 is now vas , tr3 is current driver / phase splitter . tr4 / tr5 outputs are biased in pure class A . I've built this circuit and it makes sweet music . Under simulation optimum bias current is 0.8 amps for ten watts output into 8 ohms . My question is this , do you guys like the circuit ? how would you improve it ?