Preamp Deal of the Century

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.....

Brian, the noise was a mechanical hum from the transformer in the power supply of my Supratek. Rather loud. Now there is just a faint hum that you can hear if you put your ear near the hole in the top of the power supply.

Before I could easily hear the transformer humming from my listening chair. And BTW, the AC Offset Killer didn't seem to affect the dynamics at all, nor did it seem to add any coloration.

I used solution B.

swampwalker,just wondering if you contacted Mick ,,