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Ground Loop Issues

I know this topic has been kicked around many times on this website, but I have not found the answer I am looking for. The current setup has a pair of Bryston 7B-ST monos plugged directly into a 20 amp dedicated circuit. The rest of the system is plugged into a Chang (CLS 9600)power conditioner which plugs into a separate 20 amp dedicated circuit. The rest of the system is a Denon CD player (DCD-1650), ARC LS3 or Cary SLP88 preamp. I also have a VPI table and ARC PH3 phono stage, but they have been removed from the system while I try to figure this out. Right now the only way I can get rid of the hum and noise is to use a cheater plug on the preamp (either preamp)and flip the switches to float the ground on the Brystons. I am baffled as to why I would have to float all of the 3-prong plugs instead of either the preamp or the amps. I should also mention that this same problem exist when I put my spare Hafler amp (9505) in the system. I don't think the problem is the equipment. Any advise is appreciated. Thanks, Scott
jdt332
ckoffend
684 posts
 
May not be your solution, but something I found interesting in a similar circumstance. We have a three way light (dim, medium, regular/bright) in the same room as my system, different outlet/different circuit. My wife put a standard light bulb in this lamp (vs. a 3-way light bulb). Whenever the lamp was turned on to anything less than full/regular/bright, I got a buzz through my amp.

Once we put one of those small flouresent lights into a overhead light that had a dimmer connected, whenever it was set to dim (even very slightly) it results in audible issues.

Not sure if either may be an issue in your case, but thought I would share this experience FWIW.
jbaxley's avatar
jbaxley
50 posts
 
If you have a cable box connected to the system, try a Jensen VRD-1FF Cable TV Ground Loop Isolator. See www.jensentransformers.com. After going around and around, that solved my problem -- the problem originated with the TV cable. The Jensen item costs around $70. Hope this helps.
ozzy's avatar
ozzy
7,301 posts
 
Jdt332, Jbaxley, I had the same problem as you descibed. However, I also have an outside antenna.
Finally after unplugging everything and re-inserting one item at a time , I found the problem to be the cable line and the outdoor antenna line.
So, I needed rwo of the Jensen Isolators, which cured the problem.
jea48
4,324 posts
 
Jdt332, just an added note. The ground lift switch on the Amps does not disable the safety equipment ground from the chassis.

Quote:
There are three toggle switches, two pairs of loudspeaker terminals, and balanced and unbalanced inputs on the back panel in addition to the detachable power cord. As on other Bryston amplifiers, white lacquer diagrams and instructions are printed on the back panel; an instruction manual is not needed. This is very important for the Bryston 7B-ST, which features unique optional bridging configurations for the speaker terminal hookups.
The switches select between balanced or unbalanced inputs, series or parallel operation, and a Ground Lift switch to float the chassis ground from the signal ground.

If you try my tests, previous post, make sure the Ground Lift switch on each Amp is in the closed position.

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