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From: david@daisy.UUCP (David Schachter)
Newsgroups: sci.physics,sci.electronics
Subject: Re: Audible effects in solid-state electronics
Message-ID: <2539@daisy.UUCP>
Date: 24 Jan 89 17:34:04 GMT
References: <9359@nsc.nsc.com>
Reply-To: david@daisy.UUCP (David Schachter)
Organization: Daisy Systems Corp., Mountain View, Ca.
Lines: 12

A hissing noise on a graphics product I worked on occurred only during
graphics operations; when the unit was idle, it was silent.

This was traced down to the switching power supply: when the unit was busy,
it demanded more current and the pattern of current demand fell into the
audio range.  The noise was the switching power supply responding to the
sudden demands.

Perhaps the noise you are hearing is similar?  Or perhaps DAC switching
transients improperly filtered?

				-- David "Worthless Opinion" Schachter