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Hash Filter / Diodes

I modeled this last night, and the PRV in each leg never exceeds the rating of a single diode. It's approximately the same as the output voltage (2.8 X RMS). I guess that's why equalizing resistors aren't strictly necessary when two are used in the Cit II. The A500 used single 500V diodes to produce +370V, and the A700 used single 600V diodes for an output of +410V. Today's higher line voltages squeeze those windows somewhat, so I will probably use two diodes in each leg of the A700 rebuild. The A500 can use 600V singles.

The general values you're describing for the hash filter - e.g. 0.001uF and 1mH - produce a huge output Z spike between 100kHz and 200kHz. The supply effectively turns into a current source at that frequency. I don't know whether this could have an impact on the power amp or other stages, but a 10uF electrolytic across the 0.001uF will flatten it.

Good discussion, my rebuild path is becoming clearer!



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