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Help amp hum is driving me crazy

To start with I have a B&K ref20 pre with Polk SRT speakers. I have Kimber Monacle XL and 8tc for speaker wires and Phoenix Gold RCA cables. I use a Panamax 1000 and a DBS for protection. I had a Sunfire CG with no problems but felt I needed more explosive power for home theater so I bought a used Cinepro 3K6 II. It hummed like crazy at first (50db). So I began the sytematic aproach, I started unhooking items looking for the culprit. I eventually ended up with just an amp hooked to speakers, still humming. I tried an extion cord plugged into several other outlet in the house, some worse none better. The Panamax DBS works the best at filtering out the most. I tried cheater plugs in every combination I could think of to no evail. The ground lift switch on the Cinepro helps very minutely. I tried different interconnects. What else can I do besides get rid of it or spend thousands on filters I never needed before? I am an electrician and would like to think I am fairly well schooled but I feel like an idiot.
wcj56
12 responses Add your response
mikepowellaudio's avatar
mikepowellaudio
138 posts
 
Rich,
Did you try an adapter plug which isolates the ground and only uses 2 prongs ? this will help, or should... Also, the Cinepro is a great amplifier, and I might be able to facilitate an upgrade to the amp to take care of the hum..
Let me know if you would like to find out...
wcj56 OP
47 posts
 
Well I tried turning off every breaker but the one for my amp and it didn't change anything. The satellite was causing a minute amount but I had already cleared that up. It looks as though Cinepro is not the amp for me, too bad I really like it besides the one problem. I may look into a Cinema Grande Signature, Classe CAV500 or maybe Earthquake Cinenova. It will undoubtably have to wait till after the holidays. Thanks everyone for your ideas. Rich
darrylhifi
498 posts
 
Do you have cable or Satellite TV hooked up to your system. If so remove it for the moment , because thats usually the first thing to check if its causing a ground loop. If it is there are several ways to fix it.
mrderrick
292 posts
 
No offence is meant by the call a "good" electrician. Sometimes a second set of eyes will pick up something that you might have missed. I'm also in the trade.
mrderrick
292 posts
 
Try turning off the branch circuit breakers one at a time. (leave the amp circuit on) There could be a load on one of them that is causing the "hum". My air handler had a bad solid state relay that caused exactly the same problem that you describe. (the noise passed right through a Tice) Other incorrectly wired branch circuits can also cause noise. If you isolate a circuit that is the problem, but can not figure it out, call a good electrician.
flemke
596 posts
 
What kind of lights do you have on in your house?
Halogen lights or any type of dimmer switch can cause this to happen. I finally grounded my cable tv feed to my breaker box and that made a huge difference.
Happy hunting
Tim
wcj56 OP
47 posts
 
The hum is present through all five speakers evenly. I have tried a cheater plug in every configuration possible. The external ground although not very safe does not change anything. The ground to the house is good and so is the run to the receptacle. As I said I tried several receptacles throughout the house and it was no better, infact worse for the most part without the panamax to filter. Remember the hum was not present in the four amps I had before. Thanks for the sugestions I guess I just wasn't meant to own a Cinepro.
ozfly
887 posts
 
Is it the amp itself that is humming? Or, do you hear the hum in your speakers? My amps (not speakers)hum and I was told by the manufacturer that I need to 1)Tighten up the power supply transformer (i.e., it might be loosely attached to the case) or 2) Find ways to reduce the dc voltage coming through my outlets. The only way I can think of doing the latter would be with a separate transformer coming from my sub-panel. Good luck.
tpsonic
1,092 posts
 
Had you checked the connection on your interconnects?Occasionally.the outer diameter of the female RCA connector and inside diameter of the cable connector needs adjustment.Same can be said for the center pin on your cables.Try spreading the center pin ,if it is of the expandable type and check contact of outer grounding connection.Good luck!
jameswei
883 posts
 
Perhaps the ground lead on your amp's power socket is not properly connected internally. It certainly doesn't sound like its doing its job as a ground. Try grounding the chassis separately, i.e., maybe run a wire from a chassis screw to the grounded screw on your electrical outlet. Good luck.
buckingham
333 posts
 
Lift the ground with a cheater plug.
blueswan
211 posts
 
This sounds like a problem that you cannot simply cover up with filtering or lifting the ground. You should probably consider a reputable repair shop. I am sure someone here knows of a good shop in your area. The only other alternative is to replace the unit, perhaps with another used unit from here.

Do not get rid of your filters (or buy any others) just yet. You may find they are quite helpful once your hum problem is resolved.
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