The schematic is below. The way the grounds are drawn on it are actually literal, such as the V1 cathodes grounding at the inputs (changed that, didn't help), and how the V2 cathodes are grounded at the bright volume pot. I think this is at least part of the overall issue.
If it were the heaters, wouldnt elevating the voltage at the center tap like I did the other day fix that?
No, DC elevation of the heater circuit can only mitigate buzz, the buzzy spikes at mains frequency (60Hz in your case) caused by leaky heater to cathode insulation in the valves used in early stages, particularly those with unbypassed or partially bypassed cathodes.
So how do I deal w that? I thought about bypassing V2a w a .68 cap as I'm slowly modding it towards 1987x values anyway. I've also tried a bunch of different valves in al three preamp positions w no real change.
What about putting a 3KV snubber cap across the HT mains to the rectifier?
With the heater elevation that you’ve implemented.
I had really high hopes for that as well, but it seems the factory 6.3 CT ground was just as good.
Not if it was from the heaters to other wires, elevating would only reduce hum as Pete said - with faulty tubes.
Well it could be power transformer ringing but that's super uncommon to cause problems. If it is that put a ~0.047 rated around twice the B+ so ~1200V in your case capacitor in series with a 10k resistor across the secondary of the transformer. The resistor is very often omitted but it's extremely critical, without it you're actually increasing the ringing.
No, that's up to 1 or 2. It'll get louder and louder. I can't turn it up much higher. If you look at the video I'm barely turning the volume knob.
