11/11/93
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The following text may aid you in troubleshooting some sources of noise or
may even help you to improve the overall sound quality of your GUS/sound
system performance. Many individuals who have "pops" or "buzzing" have
asked me what they can do to eliminate these annoyances from their GUS.
First, always make sure your computer is properly grounded (this may
require examination of the power supply connections) and also enusre that
the Card is securely inserted into its slot. Sometimes placing a "noisy"
internal modem or VGA card immediately adjacent to your GUS can cause
noiticeable interference. Another (less likely) source of "clicks" (or
sometimes affectionately referred to as "ultraclicks") is bad DRAM. You
can use any of the available DRAM testers to verify your DRAM is okay.
If you are experiencing bizarre sound (distorted, clipped) from the
amplified output, you may require an inline attenuator (for headphones)
or a balanced volume control (for speakers). Rarely does the sound card
itself seem to be defective, so investigate these possiblilities first
before you ship it out. Beyond that, what follows is a discussion of
a simple and effective solution to a great number of noise problems.

# Q: What is ground looping? Will it damage my GUS? or my amplifier?

	=> A "ground loop" is an electrical phrase which generally refers
	to a situation that may arise when two independent electronic
	devices are connected together. Sometimes when two (or more)
	devices are interconnected, good grounding of the devices
	is not achieved. As a result, small DC currents may exist within
	the ground plane, which a sensitive device (like a soundcard)
	will pick up as "noise". A soundcard produces an AC signal, and
	this signal may become contaminated with a DC component in such
	an event. This DC component will usually be perceived as a very
	annoying 60 Hz "buzz" or "hum". (Most of this noise comes from
	the power supply.) This noise WILL NOT damage your GUS or your
	amplifier/receiver, provided you have made the correct connections.
# 
# OK, I know what ground looping is, but exactly how do I eliminate it?  Is it
# as simple as running a ground from the PC's case to the ground terminal on my
# amp?  Probably not.. <g>
# 
	That's a good observation, and in theory, it should work. It does not,
	however, in many situations (my PC is one!). All time-varying signals
	(AC) have a "reference" voltage when they are passed to other devices.
	Usually, this refernce voltage is zero volts DC, however any non-zero
	DC component may cause a ground loop to occur (in line-level audio
	devices). The main reason a signal may have this DC component is
	because the device is not referencing (wall outlet) ground, rather
	a "virtual ground". It appears that some motherboard manufacturers
	design their bus power supplies to refernce virtual ground (virtual
	ground is essentially a DC shifted ground) instead of the familiar
	earth (wall-outlet) ground. As a result, if you connect your computer
	case to you amplifier chassis with a wire, it won't help much.
	The simplest fix I've found is to use what's called a ground-loop-
	isolator. Essentially, this little miracle is a 1:1 transformer. It
	"isolates" the input from the output by virtue of the magnetic field
	properties of time-varying electrical currents. Hence, there is no
	physical connection between your GUS and your amp, but your amp will
	be passed the full AC component without the buzz (the DC pulse, or
	ripple)! It is also sometimes called an isolation transformer,
	or an in-line noise filter. A ground-loop-isolator purifies and
	enhances the quality of your sound system, in most instances.
        Note1: the isolator is placed bewteen you GUS "line-out" and your
	amplifier/receiver's "line-in".

	You can obtain one from Radio Shack, part #270-054 for around $12 US.
	Another place to obtain one is from MCM Electronics, part #60-345
	($4.50 US) or part #60-405 ($8.95 US, deluxe, gold-plated RCA
	connectors) Order by phone 1-800-543-4330 or fax 1-513-434-6959.
	Product questions: 1-800-824-TECH (Ph. #'s should be good worldwide!)
	Note2: This info contained here is subject to market fluctuations and
	availability and I assume no responsibility for its accuracy or
	implications.

	Steve Larson  11/11/93
	Computer Engineering, Univ. of Alberta, Canada.
	larson@bode.ee.ualberta.ca  larson@amisk.cs.ualberta.ca