JC-1 mechanical hum

[Bob Stern]

The power transformer in one of my two JC-1's has a 60 Hz mechanical hum loud enough to notice 20 feet away. The other JC-1 is perfectly quiet. The amps are a year old but have had the problem since they were new.

I called Parasound's service dept. a year ago. The service rep told me a certain amount of mechanical hum is considered acceptable, so they may refuse to replace the transformer depending on their assessment of its severity. I decided to defer sending it in, hoping that Parasound would procure better transformers in the interim.

Does anyone have experience getting Parasound to replace the power transformer because of this problem?

Anyone know whether Parasound has improved the quality control on the power transformer to eliminate this issue?

Any suggestions or information would be appreciated.

[Peter Nielsen]

Bob,

The source of the problem is bad power. The PS Audio Humbuster will solve the problem and is probably a much better solution than replacing the humming transformer. PS Audio has a 30-day money back guarantee, so you really have nothing to lose by trying it...

See this thread for a long discussion about the topic: http://www.htguide.com/forum/showthread.php4?t=19605

Peter

[Chris D]

Off topic - I updated the Parasound FAQ the other day.

Would this one be worth adding to it?

[Peter Nielsen]

Chris, that's a very good idea. It really applies to all the Parasound amps with big toroidal transformers: JC-1, A51, and the A21, and let's not forget the bigger New Classic amps...

Peter

[Bob Stern]

See this thread for a long discussion about the topic: http://www.htguide.com/forum/showthread.php4?t=19605

Thanks, Peter! That thread is extremely helpful!

The reports in that thread indicate my transformer is louder than the worst of theirs, so I should contact Parasound again.

If anyone's interested, I posted to that thread some technical ideas that occurred to me after studying the thread.

The PS Audio Humbuster will solve the problem and is probably a much better solution than replacing the humming transformer.

PS Audio discontinued their $300 Humbuster. The same humbuster circuit is now available only in combination with their UPC power filter as the $500 UPC200HB. That's a steep price for a few diodes and capacitors, but it's the best solution for anyone uncomfortable building their own.