ECN Forum Forums General Topics of the Trade General Discussion Area Noise in the speakers of a dance club

If Pauluk and Big Jims suggestions don't work you may want to check the rest of the outlets on that circiut for any shorts between the neutral and the ground. This could cause the ground to be carrying some of the circiut current. Also check the circiut for any "harmonic producing equipment", lighting and dimmers have been discussed, but "electronic equipment" has not. However I think Pauluk "hit the nail on the head" (the outlet is not grounded properly at the outlet or the panel or somewhere inbetween)

Personaly i wouldnt worry about it to much, most high wattage amps generate a hum, you will probably find once the music is on you cant hear it.

worked in night clubs for about 5 years, then worked for a national company called Stage Electrics,, who hire out everything, and stage events etc..

there PA rigs hummed.. so long as your are confident all the connections tight and nothing is short circuited, i wouldnt worry too much.

we used to pick up the local taxi company through the sound system at the last night club i worked in.

Just check the socket outlet is grounded, etc or are the speaker cables running close to any mains cables.

[This message has been edited by PaulCornwall (edited 10-23-2003).]

Along the lines of Paul C's reply, I was going to mention the "Open Loop" noise of a typical Amplifier.
By this I am referring to the signal input loop being open (no connection to equipment), and not "driven to ground" as is done through a volume pot on the equipment being amplified.

Best example is a Guitar Amp(and most specific - a Non-Humbucking pickup!).
Without touching the strings, the Amp will be picking up all the stray 60Hz noise that's present.
Pull the patch cord's male 1/4" phone end from the Guitar, then place a finger across Tip and Ring; funky noise will be Amplified.

The volume pot on the Guitar will drive the power amplifier's preamp input stage to ground as the volume level is decreased (via it's internal resistance). At the end of the taper (turns), the preamp is driven to ground through a resistance of something like 250KOhms.

If the Amplifier in question DOES have its signal input connected properly and is driven to ground level, then verify the input line (signal level) is solid and hot!
Look into power quality issues only after verifying the signal input(s) are proper - as that's where the noise is coming from!

Scott35

What is driving the amplifier? Is it a microphone or an audio feed? Some balanced mic cords may have what is called a pin 1 problem where pin one is jumpered to the shell of the connector. This could cause hum. Also, any other equipment connected to this amplifier should be plugged in the same outlet to avoid any loop problems. Another thing to consider is the gain stucture of the system. There is alot of info on this thread to consider. Check some of the audio message boards like Pro Sound Web http://www.live-audio.com/board.shtml

Blessings, Mark

I went out to the club to check on the circuit that causes the huming in the speaker. And here is what i found.
H-N= 119.6 Volt
H-G= 119.6 Volts
N-G= 0.4 Volts

This receptacle makes the amplifier hum. However, when i used the three prong adapter with out the ground the noise went away.

Then i checked the extension cord that client plugs in the amplifier that DOES NOT create a hum in the speaker and here is what i found.

H-N= 120.5 Volts
H-G= 66.5 Volts
N-G= 48.2 Volts

What would cause these voltages?

And why does the amplifier/speaker hum in the receptacle that measure a good voltage and NOT hum in the extention cord that hasa the weired voltages?

Thank you
Edward

It sounds as though the receptacle from which the amplifier is run with the extension cord might be missing its ground connection.

The 48 and 66V readings are likely caused by capacitive coupling (if you're using a high-impedance meter) and/or filter components connected from line to ground in the amplifier.

The fact that deliberately lifting the ground (with the adapter) removes the hum seems to suggest either a ground loop of some kind or that the building ground is carrying a lot of noise.

The hum is still there with no inputs connected to the amplifier and the input gain controls all turned to minimum, right?

Is there a possibility that you have a ground on the speaker wiring somewhere?


[This message has been edited by pauluk (edited 11-05-2003).]

MVRANDAZZO asked a good question. What is driving the amplifier?(C.D. player, mixing console, microphone or house system?) How is it connected? (XLR, RCA or 1/4" jacks?). A "stand alone" speaker/amplifier that is supplied by one of the receptacles that you have described and is being driven by mixing console (or etc) that is pluged into the other receptacle that you have described, and are interconneccted by RCA or 1/4" or improperly terminated XLR will produce the noise you have described. The solution to the problem is "most likely""fix the defective circiut and this will eliminate the ground loop".