Noise from dimmers in Guitar Amplifier

[Dave Yurkiewicz]

Im getting a loud noise in Guitar Amplifier when 6 1000w. dimmers having 300W. bulbs are on in Church Santuary.I checked Ground and neutral (3 Phase system)its ok.I noticed when ground on 115vreceptacle is eliminated where Amp. is conected,which is a separate circuit, noise is eliminated.All grounds seem to be tied together.I left to be back later.I think its cheap dimmers.What else do i have to check to solve problem when i go back.

 

[Split Bolt]

These links may be helpful. Keep us posted.

http://www.catalinaguitars.com/electrical_hum.htm

http://www.soundonsound.com/sos/aug06/articles/guitartech_0806.htm

http://www.ethanwiner.com/dimmers.html

 

[Benton]

I haven't looked into it with any detail, but from what you said you could try running a Isolated Dedicated.....:roll:

 

[satcom]

You can first try cheap noise filters in line with the audio jack whiich run from $5 to $15 or you can go for one of these
http://www.automationdirect.com/adc...essionid=5e3016ca32cebe35e96f4e272c6d29776c49 the cheap in line audio filters usually work

 

[hurk27]

If removing the ground removes the noise then you have a ground loop, which in this case is caused by current on the grounding conductors, if this amp is an old vintage tube amp, it could be coming from it, very few filters will remove a 60hz ground loop hum in an audio system, but using a 600 ohm or 1000 ohm 1 to 1 isolating audio transformer in-line with the affected audio equipment will, so the above is about the only safe way to eliminate the hum, many of these amps reference the chassis ground to the neutral, which will place neutral current on the shielding of the audio out, and a DI to a PA system will place this neutral current into the PA system.

also be very weary of with amps with a polarity switch for the incoming power cord or a non- polarized plug on the cord, as these can place the hot on the shielding of the PA system, and make for a real dangerous situation, and a fire hazard.

 

[satcom]

If removing the ground removes the noise then you have a ground loop, which in this case is caused by current on the grounding conductors, if this amp is an old vintage tube amp, it could be coming from it, very few filters will remove a 60hz ground loop hum in an audio system, but using a 600 ohm or 1000 ohm 1 to 1 isolating audio transformer in-line with the affected audio equipment will, so the above is about the only safe way to eliminate the hum, many of these amps reference the chassis ground to the neutral, which will place neutral current on the shielding of the audio out, and a DI to a PA system will place this neutral current into the PA system.

also be very weary of with amps with a polarity switch for the incoming power cord or a non- polarized plug on the cord, as these can place the hot on the shielding of the PA system, and make for a real dangerous situation, and a fire hazard.

Yup he said the noise goes when he removes the ground, you have a very good point about the type of amp he is using, he can create a dangerous situation, in some cases, your warnings about "the chassis ground to the neutral, which will place neutral current on the shielding of the audio out, and a DI to a PA system will place this neutral current into the PA system," is something to check.

Other then the noise, the possible shock hazzard may be present.

 

[zbang]

The best solution in this case is probably an isolation transformer for the amp's power and a check for it's internal grounding (sounds like an old "hot chassis" box, which are notoriously noisy and dangerous).