Galvanic Isolation from Computer
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Lavcat

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This girl is a new convert to galvanic isolation.  Previously I had noticeable though faint noise when playing music from my Auzentech HomeTheater card through my sound system.  The noise was less than the background noise on some recordings, but still could be heard if listened for.  When the videocard switched into 3D (think World of Warcraft) the noise went from faint to objectionable and annoying.
 
What to do?
 
The first solution was to turn up ambient sounds and loop the in-game music.  This helped, but was of course a Band-Aid.
 
What worked, completely, was to isolate the sound card from the preamp.  I would not have believed the difference breaking a ground loop can make.  The soundcard background is now as black as an unconnected preamp input.  It is quieter than the SACD player input.  I tried the same experiment with the SACD and it worked too, however I have only one isolator at the moment, and there is very little noise from the SACD player anyway.
 
My system wide limiting electrical noise now seems to be from a ground loop between the preamp and the amp.  The noise in this loop is very slight, not obvious to me in normal listening, but there at headphone melting levels.  Isolating the preamp/amp connection is a future project, as is moving the Hi-Fi gear to a different outlet away from the computer.
 
The isolator that works for me is made by Jensen:
http://www.jensen-transformers.com/ci2rr.html
 
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leeperry

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But that seems to cost $200 for a stereo signal? You can get galvanic isolation over S/PDIF for far cheaper, and especially not in the analog signal path(which should be avoided).
 
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Lavcat

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Quote:
But that seems to cost $200 for a stereo signal? You can get galvanic isolation over S/PDIF for far cheaper, and especially not in the analog signal path(which should be avoided).


I paid $137.70 from Markertek.  About the same cost as just the transformers by themselves.
 
Why would you not want your analog signal galvanically isolated?  When I can afford it I plan to put a transformer between my preamp and amp as well.
 
 
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leeperry

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Well, it's good practice to avoid touching the analog signal path as this will degrade it to some extent. Most ppl will use an isolated S/PDIF or USB connection, or this kind of plug as a last resort: http://www.google.fr/search?hl=fr&q=hum%20x%20ground%20loop&spell=1&sa=X
 
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Quote:
Well, it's good practice to avoid touching the analog signal path as this will degrade it to some extent. Most ppl will use an isolated S/PDIF or USB connection, or this kind of plug as a last resort: http://www.google.fr/search?hl=fr&q=hum%20x%20ground%20loop&spell=1&sa=X

the one on the link you provided actually is a connector _without_ a ground pin :)
in fact, yes it solves ground-loop problems.
but at a price of completely removing grounding.
 
 
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Quote:
the one on the link you provided actually is a connector _without_ a ground pin :)
in fact, yes it solves ground-loop problems.
but at a price of completely removing grounding.
 


I thought leeperry's linked device was a power line isolation transformer?
 
 
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kr0gg

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grounding is quite misunderstood in audio.  galvanic isolation works really well when you use it to isolate a really noisy/dirty ground - ie a computer, whether using an analog or digital connection, since computers do not use grounding schemes optimized for quiet audio to begin with.
 
as far as trying to galvanically isolate every analog connection in your system, this may not work very well, as you really want something more like star grounding for good analog audio.  ground loops come from ground points being at different potentials, when there should not be any potential differences between them.
 
an easy thing to do is to get yourself some wire- solid core works well here, perhaps 18 or 20 gauge, and make up some runs which are bare wire at both ends.  connect one end of a wire to each component chassis, and connect the other ends of all of them together-  this tends to level any potential ground differences, and is pretty cheap toi experiement with.  the key is to make good electrical connection to every chassis- so look for a screw that is not attached to a painted or anodized chassis panel.
 
chassis ground is for safety- so you do not get electrocuted.  signal ground is defined by the circuit, and is supposed to be at 0 volts.  this is the reference for the signal.  you want every signal ground point to be at the same exact 0 reference as every other one.  tying them all together can help achieve this, more than transformer coupling every analog connection.
 
just my 2 cents worth!
 
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