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Old 10th July 2004, 09:04 AM   #1
SHiFTY is offline SHiFTY  New Zealand
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Question Fixed bias PP questions

I am building my first fixed bias amp, a PP 807. I have run it in cathode bias and want to see what difference it makes.

I want to hook up a bias meter that is switchable between the four 807s, I have a nice 0-50 mA meter that is perfect for the job.

Will it be ok to have a multiposition switch and simply switch the meter between cathode and ground for each tube? Is there any problem with clicks or pops as the meter is placed in the circuit?

The resistance of the meter is 5 ohms, I guess I will have to even that out somehow.

Also I would like to include bias adjustment for each tube, anyone got a schematic or link?
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Old 10th July 2004, 12:42 PM   #2
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I have a nice 0-50 mA meter that is perfect for the job.
Don't do that. Use a low value cathode resistor (10ohms?) and measure voltage instead.
Individual bias adjustment is trivial - just get separate pots connected to the same bias source and include individual RC /LC networks or regulators on the wipers of each pot.
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