this amp work?


2007-03-01 7:33 pm
Old circuit old transistors..70w


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2006-12-28 12:19 am
yes, it works, it's been used by many pro-audio manufacturers. it's a quasi-complementary amp with a diode stack for bias and a single ended input. it was common in the late '60s and early '70's.
Dynaco used a similar design, except theirs had a single ended power supply and a huge coupling cap on the output. the jack plug in the collector circuit was for inserting an ammeter to adjust the bias current. most pro audio designs don't have adjustable bias. they "err on the safe side" and set the output bias just at cutoff, since pro audio amps are rarely driven at low levels, so these vintage pro audio amps have a bit of crossover distortion.
Early Wem 100 watt power slaves as used by bands such as the (cream ) i.e.
Jack Bruce,Eric Clapton Ginger Baker etc used a schematic very like this !
I used to repair them I can see no advantage in going back to this scheme
Dc offset was always high and thermally unstable but I am talking re very early days in transistor amplification
regards Trev