D Basson wrote:
> Dear Robert
> I am (unfortunately?) using a CRT monitor...
> Regards,
> Diederick

I read the expert solutions offered and am reminded of "It was six men 
of Indostan" - The Blind Men and the Elephant. The exception in this 
case is that one of the solutions is probably correct: it is grounding; 
it is radiation; it is conduction; or it is something else.

Before grabbing for one solution or another, it's worth a bit of effort 
to find out what the problem is. Get a good sample of the noise and 
analyze it. If largely ~15 KHz, it's likely to be from your monitor. If 
multiples of the line frequency (60 or 50 Hz), it's likely to be hum 
with the source identifiable from the mix of harmonics. If it's related 
to audio level, it probably comes from analogue problems, presumably in 
the sound card.


Solutions follow identification. You can do it the other way 'round if 
you're lucky, but that can be slow and costly.

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