Hello all,
I have a pair of 300b mono amps that I built using skunkie's 300b schematic. I've built them exactly to spec with the 1k screen resistor and the 1meg grid leak on the 6sn7 line stage. Up until now I've been running them with a passive pre that I built with a 100k pot, so everything is essentially the same as skunkie's build except for separate enclosures. I've recently purchased a wiim ultra streamer/pre and was thinking about streamlining my whole setup by running the ultra as my volume attenuation then into my external dac and running my dac straight into the 300b amps eliminating the need for another preamp in the line. My dac is spec'd as having a 2.2v output with an output impedance of 625 ohms. Should I be looking to change the grid leak and screen resistor values in this case, or maybe just the grid leak? If so what values should I use? Is there values that would be safe to use no matter what pre I decided to use in the future? Or am i overthinking this and safe to leave the resistors on the input as is? I'm not really electronics savvy just mechanically inclined so any help is appreciated, thanks for any help in advance.
If you don't have a volume pot, just use something like a 250K for the grid leak would be my recommendation. Leave the 1K resistor alone.