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Ground Loop Hum - Partially Identified - Solution?

I recently added a new power amp (conrad johnson) to power certain speakers (fronts and zone 2). I run through a B&K AVR 507 for my HT processing and 2 channel.

I immediately noticed a ground loop hum upon installing the amp. I was able to rid myself of the ground loop hum by testing the old cheater plug route. Hum immediately disappeared.

Don't want to keep the cheater plug approach as it is just a band aid and not very safe. Is it safe to run a simple ground wire from my amp chasis to the processor chasis? This won't cause anything to blow up (you know what I mean), will it? The ground loop does not appear to be coming from any interconnects (tested by swapping out the ic's to check for this). While I know they carry/continue the loop, they themselves are not responsible for it.

Not sure how the Jensen piece works, any experience (I know a lot of people have this problem from time to time) would be greatly appreciated.
ckoffend

Showing 4 responses by bdgregory

bdgregory
1,580 posts
 
here's the part you want: Groundloop Isolation Transformer

I worked beautifully for me. $17.95 list, and they have it on special for $8.95.
bdgregory
1,580 posts
 
Looking at the specs it appears this should pass HD too!
It does indeed pass HD.

As for your amp ground loop problem, I assume your CJ amp has a captive power cord. If it doesn't, PSAudio power cords have a removable ground pin. I use them for my amps. Chasis ground for the power amp is accomplished through the interconnects to the preamp.
bdgregory
1,580 posts
 
I don't think a cheater plug is a fire hazard, but it's kind of counter logical to obsess over power cords in this hobby and put one of those in between it and the outlet.

As far as OK? goes - I was told to lift the ground by the Designer/Mfg of my power amps (EKSC Eagle 4). I had called him about hum, and he said the amp should not be grounded - all grounding should be through the preamp. He said they wouldn't ground their amps except UL listing requires it. As long as the preamp is grounded, the interconnect ground from power to pre is safety enough.

In addition, I have B&K power amps and none of them are grounded. While they have a ground capable (ie 3 prong IEC connector) power cord, they do not internally connect the ground. I'm not sure how (or if) the deal with UL listing on their amps.

Based on this, my practice has been to use PS Audio cables on my power amps and remove the ground pin. I'm not sure if anyone else makes them.
bdgregory
1,580 posts
 
Sorry Ckoffend - I hope I didn't raise too much confusion for you. My comment about B&K amps applies to their POWER amps, not receivers or preamps. I should also say that my statement is based on my experience opening up several B&K amps I've owned - the newest of which was a 2003 vintage. Based on how they are wired I assumed this is simply a B&K practice for power amps. The preamps I've owned have indeed been grounded. I've never owned a B&K Receiver, but based on your experience I would conclude your 507 is grounded - else the cheater plug would have no effect.
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