AC unit affecting amplifiers

[joeygiants]

I have been working in a church where whenever the central ac unit kicks on it causes the amplifiers for the sound equipment to go crazy and buzz until it kicks off.This is a 220 volt ac unit. What would most likely be the reasoning behind this? The sound equipment is plugged into a few receptacles that is on a totally different circuit. I plan on running brand new circuits for the amplifiers but I am not sure if that will solve the problem. How should I troubleshoot this problem? Thank you.

 

[petersonra]

a couple of thoughts.

-look for bootleg grounds somewhere. would not necessarily have to be on any of the a/c or amplifier circuits

-check and see if someone ran power to an amplifier in the same conduit as power to the a/c

If nothing obvious shows up, I would try adding an RFI filter on the power feeding the amplifiers and see if that helps any. Probably a lot cheaper than running new circuits, and a lot simpler.

 

[joeygiants]

Believe it or not both circuits are running through a piece of copper tubing about 1 1/2" diameter for about 6' to get from one side of a hallway to the other. There is about 6 romex cables running through this tubing. Whoever did this work before obviously should find another occupation.Thanks for your help. I would still like to hear a few more opinions.

Thank you

 

[petersonra]

Believe it or not both circuits are running through a piece of copper tubing about 1 1/2" diameter for about 6' to get from one side of a hallway to the other. There is about 6 romex cables running through this tubing. Whoever did this work before obviously should find another occupation.Thanks for your help. I would still like to hear a few more opinions.

Thank you

while it may not be a listed raceway, as a means of protecting and supporting the Romex, it works, and does not by itself introduce a hazard. Is the copper tubing bonded to an EGC? I am not even sure it violates any code.

 

[infinity]

while it may not be a listed raceway, as a means of protecting and supporting the Romex, it works, and does not by itself introduce a hazard. Is the copper tubing bonded to an EGC? I am not even sure it violates any code.

Sounds compliant to me.

 

[joeygiants]

When I tested the voltages at the receptacles I only got 104 volts between ground and hot compared to 115 between neutral and hot. Would this problem with the ground be causing this disturbance?

 

[petersonra]

When I tested the voltages at the receptacles I only got 104 volts between ground and hot compared to 115 between neutral and hot. Would this problem with the ground be causing this disturbance?

thats very odd. i wonder if the neutral and ground got swapped?

 

[77401]

Any Audiophile will tell you the absolute necessity of dedicated circuits with full sized grounds for the audio equipment.
Being that I'm half deaf, I can't hear the difference, but the customers I have made this repair for, swear by the improvement in sound quality.

 

[noxx]

When I tested the voltages at the receptacles I only got 104 volts between ground and hot compared to 115 between neutral and hot. Would this problem with the ground be causing this disturbance?

Almost assuredly.

 

[noxx]

As the unit in question in is fed in romex the answer is almost certainly "no", but I have to ask. Does the central AC employ an external VFD?

 

[petersonra]

Any Audiophile will tell you the absolute necessity of dedicated circuits with full sized grounds for the audio equipment.
Being that I'm half deaf, I can't hear the difference, but the customers I have made this repair for, swear by the improvement in sound quality.

they will also swear up and down that gold plated connectors make a big difference in sound quality too.

some even have gold plated connectors on their outlets. Not sure how that does anything since the gold plating is only at the outlet and nowhere from the Cb to the outlet.

dedicated circuits are a good idea. i don't believe the size of the ground wire makes any difference whatsoever.

 

[karl riley]

Also consider that if you have any net current on a circuit that shares a conduit with the AV, the induced noise is much greater. To check for net current, just clamp your ammeter around the total circuits using the conduit. If you get a reading other than zero, clamp the individual circuits to see where the net current is coming from. Once found, clamp on individual conductors to find if some neutral current is missing or is carrying extra.

Causes of missing neutral are neutral to ground somewhere in the circuit (other than at the service panel), or two neutrals from different circuits wire nutted together. Or mixed up neutrals.

Karl

 

[bimmer528]

a dedicated line on its own breaker to your outlets that your audio feeds from. A amp draws a lot of power and a number of things on that same line could damage your amp when you first power on your amp. Is your equipment located very close to your condensor? Your foundation may not be thick enough to block the electrical noise from the condensor motor which is a pretty good sized magnet. Certain equipment is more prone to others. I used to own a huge adcom amp that hummed. A line conditioner from monster power (monster is the devil http://www.sfgate.com/cgi-bin/artic...hive/2004/11/08/BUG1J9N3C61.DTL&type=business) did not fix the problem. I switched to a rotel amp which uses a two prong plug and that amp was silent. Even switched to a empty audio source (extra video source not used) and the volume at max, i heard no static or interferance.

For audiophiles that spend a ton of money on thier gear. Best thing to do is run a dedicated line and install a voltage regulator or conditioner at the service box's end.

 

[JeffD]

Where are your sound/mic/speakers cables running. If they are near the power cables for the a/c unit you might be picking up interference. I once had a sound masking system making awful noise whenever a microwave would go on. We just wrapped the cable in aluminum foil and it stopped. The microwave was 6' from the cables. Another idea if it is interference with your system cables is to try a 60 hz filter.