Newsgroups: rec.audio.tech
Subject: Re: Sound out from computer to receiver - hum is heard!
References:    <%[email protected]>
"Jerohm"  writes:

> >> "LarryLOOK"  wrote in message
> >> news:[email protected]...
> 
> >
> > Thanks for reply.  It's not exactly what I hoped to hear, but I suppose 
> > it's
> > probably the truth.  Can you or anyone make any suggestions about an
> > external solution (preferably USB)?  What terms should I search for using
> > Amazon?
> >
> >
> The M-Audio Transit will give you both analog and optical digital 
> Inputs/Outputs.  Edirol also makes various devices.  The Xitel Analog HiFi 
> Link is probably the cheapest (analog out Only).  Check around (eBay too) 
> because the prices can vary quite a bit.  There may be others also (Google: 
> USB Audio).  There are MANY USB audio devices, so find the one that provides 
> the features you are after.   The M-Audio Transit @ $79.00 is pretty tough 
> to beat (and even though you may not need digital I/O now, it is nice to 
> have!).  I am using the M-Audio Firewire Audiophile and am very pleased wih 
> it (but it is probably MORE than you are looking for).  I have never used a 
> USB audio interface, but so much stuff is out there, that it MUST work okay.
> Search around for reviews.  Good Luck.

The original question had humming noise when computer was 
connected to mains outlet. Most propably the problem is related 
to ground loop problem. 

If the ground loop problem is the reason, then generally the 
problem does not go away by using external USB audio device 
with line output. Both on the USB audio adapters and the PC 
soundcards (all I know this type of devices) the audio 
output ground is connected to PC case ground 
(which gets connected to mains ground through power 
lead ground pin). In this kind of connection both 
internal sound card and USB device would make the noise. 

Generally the best way to get rid of ground loop problem is to 
isolate the audio signal using audio isolation transformer. 
This gets rid of the grounding related noise. 
Usually this is done using external audio isolator adapter 
(theoretically this function could be built into USB audio 
device or PC soundcards, but I don't know any product that does this).

If you can make the connection using optical digital 
interface, that connection will carry sound as well 
without noise. 

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/