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From: "Michael R. Kesti"
Subject: Re: So what's the problem with just connecting the speakers from the
computer into the home sound center?
Date: Mon, 28 Oct 2002 11:48:54 -0800
Organization: MK Associates
X-Mailer: Mozilla 4.7 [en] (Win98; I)
Nico Coesel wrote:
>firstname.lastname@example.org (Adelantado) wrote:
>>So, you want to hear sounds from the internet on your fancy, expensive
>>and high-end home sound system.
>>What is really wrong with just connecting the computer's sound output
>>into the inputs of the sound system? Seems to me that most home sound
>>systems have front-end protection to permit this sort of thing.
>I've never had a different setup, even back when homecomputers
>dominated home computing.
>There are a few pitfalls though; a PC is usually earthed. Cable TV /
>Radio is earthed as well.
Sure, but who mentioned cable?
> When both earth conductors are tied together
>they form a ground loop which produces a lot of 'hum'.
Ground loops occur any time that a device is grounded through more than
one path and those paths differ in potential. The amount of hum that
results is a function of the grounds' potential difference.
> These earth
>connection must be broken. The easiest and safest way to do this is to
>insert a special 'filter' into the cable from the Cable TV.
It's a galvanic isolator, rather than a filter. For an inexpensive
solution that works well, see: http://www.dplay.com/tutorial/cablehum.html
Whether one will experience a hum problem when connecting a computer to
a home entertainment system depends on whether the earths to which they
are connected differ in potential. If so, one may use audio isolation
transformers to provide galvanic isolation, but these are not commonly
available and tend to be a bit expensive. A more practical solution is
to power the computer and the home entertainment system from the same
A problem I detect with this thread is contained in the subject line.
One should not use a sound card's speaker outputs to make this connection.
Line outputs are a far better choice as they are more likely to be
compatible in terms of impedance and signal level.
Michael Kesti | "And like, one and one don't make
| two, one and one make one."
email@example.com | - The Who, Bargain
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