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Help needed with 50hz hum/buzz in Tube system

My high power tube VTL system is not quite there. I ran seperate outlets on different ciruits for both Mono block amps and the Digital front end which runs through a panamax 5500. The problem is that there is a 50hz buzz/hum comming through both speakers the woofer and tweeter. I connected an ipod to the amps directly and they have a silent background, But when the preamp in connected to the amps the hum returns. The turntable / phono section is even worse. Someone told me that there is a possibilty that the isolated outlets are wired on "opposing legs" of the incomming 220 line.

This afternoon this afternoon I removed the ground pin of the PS audio power cables and problem solved. It seems that Every component in this system must have the ground pin removed, because one I connect another component that is grounded the problem returns.

Any suggestions on what the proper fix to eleviate this issue should be? Thanks again to all for their time

PS if you are a professional electrician working in the rockaways/LI area and would like to take a shot at fixing this let me know
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13 responses Add your response
peaceunderearth
4 posts
 
I am having the same problem with my McIntosh C-2200.
I had a dedicated AC outlet installed. I still have the hum. I used cheater plugs and it reduced the level of hum. I notice that with my Velodyne DD-15 hooked to the aux pre-outs, the hum is present with the pre-outs switched on, but not present with them off. I have used different patch cables on the DD-15, but still have the hum.
The hum only happens on tube warm-up. When the C-2200 is "warmed up", the hum goes away...
I'm going to Radio Shack 1st thing today to get the ground isolation transformer. In any event, it can't hurt, right (?)...
audphile1's avatar
audphile1
4,922 posts
 
you're welcome
weiserb's avatar
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weiserb OP
476 posts
 
With cable disconnected the problem is solved. I need to get one of these Jenson Isolation transformers Thanks !

http://www.jensen-transformers.com/
audphile1's avatar
audphile1
4,922 posts
 
In your previous post you said you will disconnect the cable from the cable box. Has this been tried already?
weiserb's avatar
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weiserb OP
476 posts
 
Update. I spoke to Ryan at PS Audio and he said that there is a different grounding potential on the circuits powering the front end and the power amplifiers , and an electrician should correct the above and add an isolated grounding rod for all circuits for the stereo. In addition as mentioned above connecting the cable line may reintroduce the problem and require an Isolation Transformer from the Jensen company.
audphile1's avatar
audphile1
4,922 posts
 
Weiserb, you have to take the coax cable out of the box. Disconnecting the receiver to preamp connection will not do. It is not on the connection level.
Please take out the coax cable from the cable box and re-check.
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weiserb OP
476 posts
 
I did already disconnect the link to the cable by removing the connection between my receiver and my preamp. that did not change anything . Only removing the ground pins solved the problem. I can disconnect the cable line and see if that changes anything. I think it has something to do with the way the outlets are wired to the electrical panel. FYI I looked up ground loop on Wikipedia and got a ton of really cool stuff to read on ground loops, detection devices, and more. probably 50 pages of information. But my # 1 trusted source is Audiogon. I have never had an unresolved problem once posted here.
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swampwalker
5,138 posts
 
I suspect it is the cable TV and there is a very easy fix. If after trying Audphile1s suggestion and finding it works, just get a ground isolation transformer for the coax. From Rat shack $10 from Modial (called Magic) $100, lots of others at in between prices.
jea48
4,425 posts
 
01-21-07: Weiserb
The cable runs into the HT receiver which also ran to the Preamp but that does not seem to be the issue.
The cable may very well be the problem. A difference of potential, voltage, between the signal ground of the cable coax and that of the equipment/signal ground of your audio system. Disconnect the cable TV coax from the HT receiver, if the hum goes away it is the cable that is causing the problem, not the grounding system of your home. Post back your results....
jond's avatar
jond
5,798 posts
 
Removing the ground pins is the exact same thing as using cheater plugs, you've broken the ground. No hum but it's fairly unsafe. It likely is in fact the cable, but having an eletrician out isn't a bad idea if you can afford it, he should be able to offer a safer more permanent solution. Good luck and happy listening!
audphile1's avatar
audphile1
4,922 posts
 
Wait with the electrician. Try this first.

disconnect the coax cable(cable tv) at its first point of entry into your house. Unplugging the cable box won't do. You need to take the coax cable out.
Then put the ground pins back on the PS Audio cables. Turn on your stereo system and see if it humms.
weiserb's avatar
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weiserb OP
476 posts
 
The cable runs into the HT receiver which also ran to the Preamp but that does not seem to be the issue. I eliminated the problem by removing the ground pins, I would like to have an electrician come in and fix the problem, but I am not sure what I have to ask him to do. thanks
audphile1's avatar
audphile1
4,922 posts
 
it's probably a ground loop. You can either use cheater plugs or you need a ground loop isolator. Is the cable tv near by the system?
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