HiFi Hell 2: Ground Loop Boogaloo
February 4, 2015 4:33 AM Subscribe
I can't seem to eliminate this hum/buzz in the phono stage of my stereo receiver.
I've got a small setup consisting of an old NAD 7250 and a new Rega RP1 turntable. Everything works great, until I plug something into the phono input on the receiver.
Even just RCA cables with nothing plugged into the other end will cause a pronounced buzz. Wrapping both hands around the cables makes it much worse. Hooking a spare speaker wire up to the ground terminal on the receiver and holding the bare end in one hand and wrapping the other hand around the ends of the RCA cables all but eliminates it. Same goes for when the turntable is hooked up - holding the ground cable and standing next to the tonearm and putting my hand where the phono cables leave the plinth also eliminates it. That leads me to believe this is a ground loop issue but everything I've read about solving it doesn't seem to help at all. Is there anything I'm missing?
I've got a small setup consisting of an old NAD 7250 and a new Rega RP1 turntable. Everything works great, until I plug something into the phono input on the receiver.
Even just RCA cables with nothing plugged into the other end will cause a pronounced buzz. Wrapping both hands around the cables makes it much worse. Hooking a spare speaker wire up to the ground terminal on the receiver and holding the bare end in one hand and wrapping the other hand around the ends of the RCA cables all but eliminates it. Same goes for when the turntable is hooked up - holding the ground cable and standing next to the tonearm and putting my hand where the phono cables leave the plinth also eliminates it. That leads me to believe this is a ground loop issue but everything I've read about solving it doesn't seem to help at all. Is there anything I'm missing?
Response by poster: Sorry, I meant to add that the turntable doesn't have a ground wire or anywhere to attach one.
posted by Venadium at 4:57 AM on February 4, 2015
posted by Venadium at 4:57 AM on February 4, 2015
That sounds like your problem - can you try wrapping a speaker cable around the ground tabs on one of the RCA plugs going into the turntable, then connect the other end to the ground terminal on your receiver?
posted by steinwald at 5:00 AM on February 4, 2015 [1 favorite]
posted by steinwald at 5:00 AM on February 4, 2015 [1 favorite]
This ground loop isolator would accomplish the same thing, and would be a bit less kludgy:
http://www.crutchfield.com/S-NLZ97wTlVQB/p_127SNI1/PAC-SNI-1.html
posted by steinwald at 5:06 AM on February 4, 2015
http://www.crutchfield.com/S-NLZ97wTlVQB/p_127SNI1/PAC-SNI-1.html
posted by steinwald at 5:06 AM on February 4, 2015
I know that if I plugged my amp and my Theramin into the same electrical circuit that I'd get a ground hum/buzz. I'd plug the amp into one circuit and the Theramin into another and the problem would be eliminated.
So perhaps plug the phono into one circuit and the receiver into another.
Long shot, but it might work.
posted by Ruthless Bunny at 6:13 AM on February 4, 2015
So perhaps plug the phono into one circuit and the receiver into another.
Long shot, but it might work.
posted by Ruthless Bunny at 6:13 AM on February 4, 2015
Response by poster: I don't want to threadsit so I'll try to keep these replies to a minimum, but is it possible that it's something other than a ground loop if I'm getting the same buzz even with bare RCA cables plugged into the phono stage? Also, with the turntable plugged into the receiver, I get the same hum whether or not the turntable itself is plugged into an AC outlet.
posted by Venadium at 7:20 AM on February 4, 2015
posted by Venadium at 7:20 AM on February 4, 2015
Bad rca cable? Dirty/corroded rca ports?(my big 120wpc 70s technics in my workshop gets this a lot)
Have you tried placing the receiver on an isolation transformer like a powervar? I swore by a big ISObar one of those ahead of my little tube amp. Pc recycling shops often have them for cheap, like $25 for one rated at a few amps.
I have not slayed this issue with my phono preamp going in to a modern home theater receiver. The rca cable, even when attached to nothing, appears to be acting like an antenna. If you haven't checked that other stuff though it's worth a try. The corroded rca port acts exactly like this until I clean it a bit too.
posted by emptythought at 5:20 PM on February 4, 2015
Have you tried placing the receiver on an isolation transformer like a powervar? I swore by a big ISObar one of those ahead of my little tube amp. Pc recycling shops often have them for cheap, like $25 for one rated at a few amps.
I have not slayed this issue with my phono preamp going in to a modern home theater receiver. The rca cable, even when attached to nothing, appears to be acting like an antenna. If you haven't checked that other stuff though it's worth a try. The corroded rca port acts exactly like this until I clean it a bit too.
posted by emptythought at 5:20 PM on February 4, 2015
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posted by steinwald at 4:55 AM on February 4, 2015