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Kurt Nauck wrote:
> We are doing some re-arranging of our studio here at the shop.  We're 
> encountering hum from the audio cables being in proximity of power 
> cables and possibly from florescent lighting (!)   Is there some way to 
> shield audio cables from the influence of power sources?  I've read that 
> one should always cross audio and power cables rather than having them 
> run in parallel.  Any suggestions would be appreciated!

Some suggestions:

1. Get the waveform of the 'hum' to determine if it's from conduction or 
radiation.

2. Conduction: If the cables are shielded, check for common grounds and 
related grounding problems. In particular, if two or more channels are 
being used, verify that only one ground is active per device into which 
they're plugged. Check your power line (mains) for excessive noise.

3. Radiation: Try repositioning cables. If that changes the hum 
(quantity or quality), then look into either balancing the lines or 
shielding the offending source.

4. Otherwise: Related sources include television receiver/monitor or 
computer monitor. Look for a peak at horizontal sweep rate (~15 KHz); if 
present, you may have vertical sweep (50 or 60 Hz depending on your 
power frequency and the nature of the device). Other local equipment may 
also induce noise either on power lines or radiated. Fortunately, they 
are less probable than simple conduction and radiation.

Mike
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