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Re: Sonic Observations - Replaced Selenium on PAS

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Well, when I replaced the filament voltage doubler with 6A2 6-amp 200 PIV diodes. I also use two 4700UF caps with 1.5 ohms resistance @ 10-watts installed in the transformer lead that goes to the center position of the two caps in series.

This resistance lowers the voltage to 12.6 volts as solid-state replacement rectifiers over-voltaged the tubes with my modification. Another benefit is lowering the high peak to average current. This is easier on the transformer & reduces noise as well. My preamp produced no audio hum after modifications.


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