Preamp Deal of the Century

Bwhite- this is new. I had used the Berning and the Joule with no problems. Then the Joule crapped out and went home to Jud for repairs. When I hooked it up upon return, BUZZZZ. Its from the amp, not the speakers. Swapped in a new (old) pre, dead quiet. Upon Jud's suggestion, I powered the Supratek via (gasp!!!!) an old extension cord from another circuit. A little buzz at the amp, but in playing around with home made noise detector (a length of old hose held up to the ear), I was able to track the predominant noise source to the power supply stage of the pre-amp!!! Further testing showed me that it is coming from inside the pwer supply, up through the vent (?) slots in front of the rectifier. NOt sure I want to fish around further in there with power on and high voltages, but does anyone who knows how these things work have any ideas?

Swampwalker,

I had the same problem. It was DC on the line. I fixed it with a combination of the 'Ah! AC Offset Killer' and an isolation transformer. The 'Ah! AC Offset Killer' seemed to be 90% of the cure.

Now there is just a teeny hum that you have to listen very carefully to hear. I mentioned this fix to Mick soon after I got my Supratek and he said he would look into it. Not sure what happened after that.

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.