This quote you put in your question was from a post I did quite a few years back
The other thing to consider is that there are other voltages in the amp besides the B+ voltage, and if you are going to play around with the AC supply with a variac, then it will affect these voltages too. The bias voltage, the heater voltage.....all of these will change if you change the AC supply, but they won't change linearly....in other words if you change the AC supply by 5 volts, it doesn't mean than the DC voltages in the amp will change by the same amount, and the AC voltages like the heater also won't change in proportion necessarily. The bias would also have to be readjusted to run the amp at whatever lower voltage you plan to run it at, and once that is done you can never run it at a higher AC supply without readjusting the bias.
It is much easier to go with series connected caps for the first two filter stages in the amp and get 700v rating, use a 500v cap for the third section, and a 450v cap for the last section. The can caps are stressed in these amps and discrete caps are much cheaper anyway than cans these days. Another possibility you might consider would be the cap boards the Triode sells. Personally on the Sunn bass amps, I like using higher filtration in the plate and screen supplies, which are the first two stages. The bass tightens up and the hum goes down....though if you decide to do this using a solid state rectifier is mandatory if you go over 60uF filtering on the first cap stage.
I was specifically talking about if someone was going to use a variac to adjust the line voltage down below whatever it was at the wall to power the amp, and also was talking about upgrading the caps in the power supply and the things to consider if doing so. I don't recall what the rest of the conversation was about in this thread though.
I agree with Loudthud here. There are some technical questions that must be answered about how your amp is wired, and the caps in the power supply must be in good shape to be able to use the Rockcrusher without voiding Rivera's warranty from what I can see. So you need someone knowledgeable in vintage Sunn amps to take a look at it and see the condition and how the output is wired before you can proceed further. The info you quoted from me might come into play if you need to change the electrolytic filter caps in the power supply, and you need to understand what is trying to be done and the advice I am giving to be able to proceed from there. Any good tech should be able to understand it, so if you don't think you have the chops, then please find a good tech. I'm willing to explain further from that quote if necessary but in order for any of us to help adequately, we need you to consult with a good tech to provide the info we need.
Greg
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