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In the Forum: Melquiades Amplifier
In the Thread: Single-stage Melquiades vs. DHT amps
Post Subject: Split balancePosted by floobydust on: 5/11/2009
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Romy,
No easy drawing program available this second (traveling for 3 weeks) but I can send you a simple schematic in PDF if you like via email. In any case, to adapt what you have already have to the split biasing, just remove the cathode bias resistor from the hum balance wiper and connect it to the filament center-tap. This results in a fixed DC balance against the DHT filament and the balance pot now provides an adjustable AC balance only. In many cases, I've gotten better results in hum nulling this way, but it still requires good tubes.
On a second note, you can also modify this for both adjustable AC and DC balance on seperate potentiometers. Both potentiometers would be in parallel with the filament (and padded) but you use the wipers independantly, i.e., one has the bypass cap attached and the other has the cathode bias resistor attached.
Regards, KM
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