Question for the brain trust

[Unit 148]

If you have 16 matched output transistors in a push pull PA can you optimise bias with a single pot

as in my amp here;

or is there an advantage in being able to set the bias to each pair of devices?

Phil
Unit 148

 

[Unit 148]

I should of said 8 transistors in my amp. :blink:

Phil

 

[bob85]

there may be a small advantage if you feed each pair with an active regulated and thermal tracked bias circuit,
with a single bias supply using exactly matched devices you will still have a slight inballance of idle currents anytime there is a thermal differential across the heatsink where the transistors are bolted,
i doubt it will sound any better unless the stock circuit is crap.

 

[Toll_Free]

Unless you mount a thermistor to EACH device, or pair of devices, you won't gain much by setting the bias independently... The reason being, you will be tracking HEAT SINK temp, which is a culmination of ALL of the transistors.

That being said, I do put a single 6A10 from the bias buss to each transistor pair. This keeps one CB shorted transistor from taking out 8 (I have 2 banks of 8, each bank of 8 is individually biased, only because I could only source 5A CCS regulators).

--Toll_Free

 

[Unit 148]

Thanks guys.

That's answered my question.

Phil
Unit 148