Audio Ground Loop Noise and electrical supply wiring question.

markebenson

Senior Member
Location
fl
Audio ground loop noise is a common problem in bars / nightclubs as a majority of djs bring a laptop with a 1/8 unbalanced jack to plug into the house system .

I have a tech that insists that if all audio equipment is connected to the same phase that there is not a possibility of ground loop noise. I am not so sure.

Please provide your input on different scenarios on a wye / delta system, etc providing power to the audio equipment and ground loop noise.


(No comments on balancing the electrical load please. The load is quite small anymore as the audio power amplification is electronic).

Thanks, MB
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I don't really understand why the audio amplification being described as electronic matter all that much as far as load balancing goes. You're going to need the same amount of power to get the same amount of sound pressure.

I don't think the tech understands what ground loop noise is or how it gets into the system. The best thing you can do is isolate your input from the line power. That eliminates any possibility of ground loop noise being generated.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
In addition to adding an audio isolation transformer, the signal-to-noise may be improved by keeping the audio level from of the laptop reasonably high and then reducing subsequent gain as needed. Of course the drive level must not be too high or that will cause distortion.
 

AdrianWint

Senior Member
Location
Midlands, UK
I don't really understand why the audio amplification being described as electronic matter all that much as far as load balancing goes. You're going to need the same amount of power to get the same amount of sound pressure.

I don't think the tech understands what ground loop noise is or how it gets into the system. The best thing you can do is isolate your input from the line power. That eliminates any possibility of ground loop noise being generated.

Are you confusing a 'balanced line' audio system - a means of sending audio over a cable system that has both in-phase & anti-phase components of the audio signal with balancing the electrical load on a MWBC or similar?
 
I have a tech that insists that if all audio equipment is connected to the same phase that there is not a possibility of ground loop noise.
They are, of course, wrong (take the A phase from one panel and the A phase from another....). Same phase doesn't matter, however using same power connection means that all of the power and ground leads radiate out from there and there's less opportunity for induced hum/noise. Delta/wye supply doesn't make the tiniest bit of difference.

If the DJ is using a laptop, the audio output is already isolated from the power line (and most laptops use a 2-wire power cord, anyway).
The audio outputs of most laptops are CRAP, I've never met a professional DJ that doesn't use an external audio box, which are usually isolated by design.
High signal levels are your friend, makes the noise floor relatively lower.

The problems usually happen when the "tech" tries to run the unbalanced line more than maybe 6' to their gear; that's a recipe for failure (and hum).
 

romex jockey

Senior Member
Location
Vermont

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