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Buzz/hum caused by new a electric lines



On Thursday I decided to run dedicated 10 gauge lines on 20 amp breakers for each amp (Joule Rite of Passage)and a separate line for the front end (Jadis preamp). Well, everything seemed to be fine except for a buzz/hum in the right speaker. I searched for most of the usual suspects accompanying electrical noise. First thing I did was remove all interconnects from the preamp. Hum was still there. I muted the preamp and found a very quiet buzz from the amps alone. Only audible if I stick my head into the speaker. I tried switching the left and right interconnects from amp to pre. The buzz moved to the left speaker. I thought it may be a ground issue, so I dropped all grounds. No change. I tried different ic's. No change. I plugged preamp into a completely different set of outlets with different power cord. Buzz persisted. Swapped all cords with no success.

One thing I did notice was that as I turned the left amp off (variac controls power)the buzz decreased by nearly half. These amps/system were very quiet prior to the wire change. What could I possibly have done? I am still unable to determine if the buzz originates in the amps or preamp or a combination. Just so odd it should be isolated to one channel. One other thing I tried was physically moving and switching the amps and found the buzz stayed on the right side.

Any help you can offer would be greatly appreciated. The buzz goes somewhat unnoticed when the music is on, but in between cuts it is quite annoying.
siddh
newbee
4,767 posts
 
My personal experience. For a short time I ran all of my source equipment from dedicated lines with the amps on a seperate line thru an 'amp' filter. Unresolvable hum! I ran a line from the filter back to the dedicated line and the hum went away. I have since read of others who have also concluded that the amps and pre's/sources can sound better when they are all on the same dedicated line, everything else being equal.
ngjockey
1,042 posts
 
Are all the new lines on the same phase? There are two phases coming into residential.
albertporter's avatar
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albertporter
4,949 posts
 
Ngjockey asks the exact question I would ask.

It's possible your electrician delivered two phases to your system and you now have a ground loop.

If you can, plug everything into one outlet and see if the problem is resolved. If your power draw is too large or you don't have an extension box that allows space for all your cords, you might use a VOM and test the voltages on each outlet.

Typically the two phases are not the same voltage and you can figure out which phase is going to which outlet by reading it. Of course very long distances between the box and outlets (such at to opposite side of the home and upstairs) can drop voltage too, but within a similar distance the voltage coming off the transformer is usually much greater than distance drop.

Once you determine which outlets are the same phase, plug all your stereo gear in and see if the problem is resolved. If this fixes it, the electrician can swap the wires of your stereo dedicated run at the breaker box for the next breaker "down" to get all on the same phase.

I have 14 dedicated runs for just my stereo system and all of them with the exception of the TV and digital are on the same phase.
nsgarch's avatar
nsgarch
2,524 posts
 
Albert's and Jockey's advice will probably do it for you, but I'd like to add a couple of refinements(?) which, like chicken soup, "couldn't hurt" ;--)

Plug the amps right into the wall. I won't go into my diatribe about conditioners/filters here, but I think they are more a liability than an asset, if you have ded. circuits anyway.

Second, if you are using single ended ic's between your amp and preamp, and if they are the "shotgun type" -- two signal conductors plus a floating shield -- (most brands are these days), point the arrows toward the preamp, not toward the amp. This insures that the shield is connected to the preamp (where it should be.) Make sure the preamp is grounded -- you can lift the other grounds safely AS LONG AS ALL IC's ARE CONNECTED; TURN STUFF OFF IF YOU ARE GOING TO SWAP/DISCONNECT THE IC's.

My $0.02.
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albertporter's avatar
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albertporter
4,949 posts
 
Nsgarch,
Plug the amps right into the wall. I won't go into my diatribe about conditioners/filters here, but I think they are more a liability than an asset, if you have ded. circuits anyway.

I agree completely.
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