If it can help you; I had similar problems with 6 step and a f@$k Hum. I changed the ecc81 quads until I found a perfect mach quad at the same time, I separated the AC lines and did a ground loop breaker. Now my amp is absolutely silent and the different between triodes is around 3~8 volt.
Ummm I'm interested. Only for 400v Psu? I'm burning some EL34 and I recognise that the sound now is much better so I'm happy however, I wouldn't mind testing your mod.
Here We use Bkool and it´s fun... but I prefer a real pelotón, people on the road, climb... ok for training it´s a help but I think that nothing can change the feeling on the real road, the mountains.
With my BH : Gershwin: Rhapsody in Blue / Barber: Adagio for Strings / Bernstein: On the Town; Candide Leonard Bernstein & Israel Philharmonic Orchestra & Los Angeles Philharmonic
Not yet. I've only been listening to it for an hour while I adjusted it. On the other hand, I would like to compare it with the GG using the same tubes... a quad of "Fat Bottomed Girls"
I'm listening to my BH right now. The offset drift a bit and you have to wait a few minutes until it stays low and stays stable. All the measurements seem correct.
It run hot, very hot, very very hot....