Bypassing the divider would have been the smart thing to do in the pre that I was struggling with (actually spending a fiver on a separate winding for the EZ80 heater would have been smarter still). As far as the bypass cap goes though I can’t think of anything that I’d expect to be significant either.
Have been round the mill so many times on this over the years and always conclude that you can hear just about everything in the heater supply, indirect or not. 317T regs sound so unmusical it’s like having an Audiolab. In the end I go for CRC supplies with nice parts as the least worst option, tried CMC in there recently and that seems to help, probably a Mayer style LCL would be better still, but big, heavy and costly…
Rebuilt the heater supplies today, they are now delivering the correct voltage and regualting properly.
Was still seeing 50Hz hum on the measurements, so decided to say fuck it and just try it in case it’s a measurement thing.
Plugged it in and HUMMMMMMMMMMMMMMMMM. Then I realised that the shelf underneath had a valve amp with an enourmous leaky EI transformer and it might not be the best idea to put an LCR stage with lots of magnetic components in such close proximity. Duh. Moved the stage 2 feet away and hum gone. It’s dead quiet now.
Listening to Tidal on my phone via the inverse RIAA. It sounds rather nice, actually.
Well, it was going so well and I was enojoying listening until I tried turning up the volume to max, when I noticed a very slight residual hum. I really want to get to the bottom of it, I suspect it might be environmental (i.e. my house/mains). Just want it to be perfect!