Adding An Extra Cap To A Power String

[rp]

I've decided to add the 8mf pre amp cap to my in progress 5C8 giving the PI it's own cap just like in the 5D8. I think this can only help without changing the original sound too much. I've never modified a power supply but I realize I'll wind up with lower voltages on the last 3 tubes especially if I stick with 10K all down the line like the 5D8.

First - good idea or bad idea to do this mod? I'm still at the point where I can change it back.

If I go ahead and do it any advice on how to do this right? Is it OK to play around w/ the values of the dropping resistors without too much consequence both electrical and to the sound/feel? Can I just use 500 ohms or 1k for the last resistor? Maybe a good idea to calculate the watts if I go very low, I'll be using 2W MO resisters.

[martin manning]

Estimating about 1 mA per 6SC7 and 4 mA for the 6J5, I get 8 mA total. You could use a 2k2 dropping resistor, and only lose about 18V. If you then used a 16uF cap I think you'll get pretty good decoupling. If you're willing to accept more voltage drop, you could use a 4k7 and 16uF and get the same effect as the 10k and 8uF in the 5D8. Power for 8 mA through 2k2 is only 0.14W so you're not likely to have any issue there.