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What's the basic principle of power scaling? I was going to incorperate some method of lowering B+ voltage in my next amp, possibly by switching in zeners or somthing. A freind pointed out the London Power power scaling stuff. I'll buy the TUT book that talks about when it's available, but currently it's not.
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Hello!
The TUT5 has the schematic of the power scalling incorporated in the "standard amp". Although if you don't understand it by looking to the schematic, it is not explained very well in that book.
The goal of the circuit is to reduce B+ and raise (less negative) the Bias voltage at the same time.
I wouldn't recomend using just zenners, I would recommend at least an mosfet with the gate referenced by zenners or by a voltage divider.
Good luck! -
Poer scaling is really only there to get the same tone at a lower volume. Here are a few other ways to do the same thing (more or less):
switching out pairs of power valves and adjusting the bias of the remaining ones in amps using parallel output stages,
using separate driver valves for the power valves in amps using parallel output stages. so the signal to one pair can be grounded, effectively turning that pair off without needing to rebais.
adding resistors in series with the speaker to soak up power,
Reducing screen volatge and adjusting bias on power pentodes,
Adding resistors in series with the output transformer to soak up power.Comment
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