[morzh]

If you want to try a bigger cap don't use it in the first position, the input cap as it will raise the dc output of the power supply and cause the BC resistor to run very hot. It's ok on the 2nd or 3rd caps.
Terry

Yes Terry, they actually rely on higher ripple and then dropout on the choke to keep the voltage about 260V at the choke output.

I actually tried (I have connected in series 4 electrolytic caps, 10uF/100V - this is what I have to experiment with) to connect it to the position right after the 80 diode tube, and the voltage jumped about 30V (320V i/o 290V).

Connecting the caps across the position right after choke (2nd cap, pins 1-4) does not change the voltage, but makes the buzzing noise less pronounced.

-----------------------

I actually found the reason for extra buzz - the short piece of wire shorting pins 6 and 4 broke, but in such a way so I did not see it. So the output of the choke was simply not filtered. I found that by checking voltages on the caps and seeing the voltage on the pin 4 being about 2 or 3 Volts. After I re-connected it with a big solder blob, the buzz subsided and the quality of the music improved.

I still have some buzz, but it is about the same it was before, and I think I will beef up that 1uF cap after the choke, maybe to 5 to 10uF, and see what happens (once I get me some good caps - ordering them from Mouser does not make sense unless order is large - they rip you off on shipping).