FIXED!
Spot on, guys. I diverted the input jumpers out the front of the chassis on twisted wires (rather than instrument cable) and then connected it round the back with longer RCA cords. The hum completely dissapeared, I mean completely dead quiet even with every buzzy awful thing in the house plugged in. In fact, I connected all the power back via two-pin in the back of my pre-amp and it still sounds *great* with an almost inaudible hum. So it looks like nearly all of the hum was induced from the PT. I still need to figure out how to reconnect the RCA jacks to the jumpers, maybe run twisted wire directly away from the PT, then out beneath the output transformer jumper. Or even all the way around the margin of the chassis tucked up near the plate. Should be a balance between shortest circuit path and keeping it away from radiation. Maybe a non-grounded conductive jacket around that as well?
I had *no idea* the PT could induce *so much* voltage into the cables. It was completely unlistenable at it's worst, and I understand why Dynaco put their input jacks at the front in their models. Next time I do one of these I'll be putting the RCA jacks on the very outside (thought still rear) of the chassis with the banana jacks towards center. And likely pivoting the PT 90 degrees for good measure (thanks for the reminder, Shannon!
) At least I have a benchmark for what this should sound like now, if my mods don't get enough mileage off rerouting the input leads, I can pretty easily and quickly slap together a new wooden surround with better interconnect placement. It's built like I do picture frames, not challenging.
And it sounds GOOOOOOD.
Bass is much tighter than I am used to, and I am no longer using the Pre-amp equalizer to compensate; it's lower and louder. Just *Brilliant.* Everything is much cleaner/crisper than I've heard before. I know what people mean when they say 'muddy' now. The top end rings less, which is great since KLFs are already tinny in the upper end. Grand improvement there. My Kenwood Basic C2 plays very well with it; I can get three quarters out of the volume pot before the room becomes too small for the decibels, which is just fine with me. Also, the speakers start doing funny things much beyond that. So, good balance all around. Tonight everything else is getting turned off so I can spin vinyl and melt into the sofa. I'll go back for a more permanent on the input leads sometime next week, just so things are cleaned up.
Since getting into this hobby a few years back I've given considerable research and thought into what I wanted my 'permanent' amp to be, and spiraled closer and closer to Dynaclones, especially the "Baby" Model. It's perfectly sized for my needs, there is lots of room to fiddle and learn and it has a great track record for just sounding *great.* There are so many options out there; rehabbing old ones, buying rehabbed old ones
doing point to point, and the variety of available PCBs out there. This is a SaWeeeeet board you've put together, Shannon. It's made both the price point and technical aspects accessible to relatively new hobbyists like me. Thanks for helping knocking an item off the bucket-list. It's a short list, but I place real importance to these things.
Thank you *both* very much for your patience and help. The body of knowledge out there is impressive, but I am always more taken with how generous people are with offering their knowledge and time. With your help we've got another gorgeous sounding ST-35 off the ground.
All the Very Best,
-Fishstix