Preamp Deal of the Century

Fiddler - Thanks for the information, I'd like to know a bit more about your solution. Was your amp making a mechanical hum, or did you hear buzz from the speakers? What isolation transformer do you use?

Do you connect the system like:

A. AC Offset Killer --> Transformer --> Supratek
B. Transformer --> AC Offset Killer --> Supratek

Swampy. What rectifier are you using and does it test strong?

Swampwalker, I understand that the buzz only happened after the Joule returned from repair, and I also assume from your answer to Bwhite that the Supratek does not do this with other amps, e.g. the Berning.

If part of a circuitry has a weak ground--for example, the return (ground) connection on an interconnect or RCA socket--then this can cause the signal to "find ground"--i.e., induce a current over dielectrics--in other parts and induce buzzing in tranformers.

Once the Joule and Supratek are connected via interconencts they are essentially a single circuit--and you are getting noise in both power supplies.

My guess--and this is simply a guess--is that either the process of connecting and disconnecting interconnects has created an intermitant short in one of them, or shipping may have caused some minor weakness in one of the many internal ground paths in the Joule. Because every component is different, it is coincidential that connecting the Yamaha C2A "curcuitry" doesn't induce errant current flows, but connecting the Supratek's does.

Try: 1) swapping a few interconnects; 2) inspecting, flexing, and testing them for continuity with a voltmeter; and/or 3) opening the Joule and looking for weak solder joint.

Current situation- I have traced the noise to the torodial power transformer on the Supratek power supply. I tested the rectifiers (about 6) that I have and unless every one is bad, my tube tester is on the blink. Anyways, it starts immediately when the power switch trips the circuit. Any thoughts?

Most torroidal transformers have electrostatic screen. Besides, it is unlikely that DC will be present at the secondary. I would suspect that it is possible one of the rectifer is bad.

If you have a scope, you can look at the ripple voltage after the filter caps or at the regulator input to each channel. Most of the time it should be small (in order of millivolts). But if you measure around 100 mV or more, that could be the problem.

Just my thoughts.....