TRL Dude or Joule 150 MKII for Major Pre Upgrade

I found a bunch of unused RCA cables and connected the ground and center wires to short the jacks. I places these on my 3 sets of unused preamp inputs. Still have the buzz. Still think this may be a good idea however.

Vett93 summed it up very well. My speaker and other cables really did not change position. My speaker cables are simply solid core copper runs and very straight forward. Changing power or ic cable brands did nothing to change the hum.

This was extremely bizarre to me...

To me as well.

Have the preamps been located close to a possible source of emi/rfi, including perhaps the amplifier itself? If that seems like a possibility, try moving the preamp to different physical locations.

Beyond that, I'm out of ideas at this point.

Best regards,
-- Al

From the descriptions above, IMO the preamp is off the hook- this is a problem with the power amp.

Also based on these descriptions, its my theory that the amplifier has a problem with noisy rectifiers, which is getting picked up at the input if the source impedance is too high. This is why it is quiet with a shorted input and a 1K resistor, but not with the Dude (which has a relatively high output impedance as the volume control is at the output of the preamp), and likely a few other tube preamps as well.

Noisy rectifiers can be tricky as the commutation noise they produce acts very much like RF (which *is* part of their noise component), in that it can easily get to other parts of the amplifier, and use input connections as an antenna.

However this is only a theory, another possibility is a layout problem where the AC power is somehow too close to the audio input. Either way though- things are pointing at the amp.

grid stop resistor on the 6SN7 of the Aesthetix
OR less likely...
RCA connector on the Aesthetix shorted audio ground to chassis.