Newsgroups: rec.audio.tech
Subject: Re: Schematics for basic components?
References:   
"Chris Fewer"  writes:

> "r.crowley"  wrote in message
> news:[email protected]...
> > "Chris Fewer" wrote in ...
> > > Anyone know a web source for some schematics for building basic
> > components?
> > > And/or basic diagrams for wiring for audio?
> >
> > You would have better luck asking for specific things.
> > But two of my favorite audio websites are:
> > http://sound.westhost.com/projects.htm
> > http://www.epanorama.net/
> 
> Well, I'm looking to add XLR and RCA I/O to the front of my PC.
> 
> As I'm primarily involved with a video field, my audio construction
> experience is limited to "soldering by numbers" to make cables, or, simply
> replacing burnt or missing pieces... so I figure assuming I've got some
> basic instructions in front of  me, it shouldn't be too hard.


RCA I/O to the front of the PC easy option for most soundcards:

Buy two cables intended for PC to stereo equipment interconnection
(ones with one 3.5 mm stereo jack and two RCA jacks).
Remove on plastic faceplace from your computer (those which
are in front of the the empty slots for CD-ROM / dirsk drive places).
Select suitable connectors you want to use (two RCA or 6.3 mm 
jacks for both input and outputs, makes to tatal four connectors).
Drill holes ot the plastic and put connectors there.
Cut out the original RCA connectors from the cables
you bought and solder the wires to the connectors you 
just installed to the faceplace on the computer.
The cable shield goes to the connector ground and center
wire goes to the connector signal pin.
When you have made this you need to secure the wires
so that this thign will take some use (some insulation
tape, shringing plastic tuing, cable tiers, possibly hot glue
or nice case etc.). Whaever ou fell is needed to make
this thign to take enough use in you application.

Connection to soundcard: 
Take out one card slot cover from the back of the computer.
Route the wires from the front of the computer
through that empty card slot to the back of the soundcard
where the 3.5 mm audio jacks are. Now you have everything
working.
If you wish to put the slot back. yuu need to make suitable
holes to the side of the slot cover to let the wires to
pass out here (remebr to put some plastic or rubber
around the cut metal part so that the sharp metal does
not damage your cables).

And now you have working system for most of the sourcard.
With some soundcards you have option to get the same
signal signals that go/come from the soundcard connectors
also in special connectors (usually just row of pins)
from inside computer on the spoundcard itself. Check manual
or web document on your soundcard. By using the connections
on soundcard circuit board you can avoid the annoying
cables from the back of your soundcard to inside of your 
computer. Using inside connections is usually more reliable.

This was my tip for frontpanel audio connections using
RCA connectors or 6.3 mm connectors.


XLR option:

If you plan to use XLR connectors, then it is somewhat
different story. The basics are the same, but you will
need a high quality audio transformer between the 
XLR output connector and soundcard connection.
This transformer will provide the balanced-unbalanced
adaptation needed (XLR interfaces should be balanced).
The audio transformer (1:1 works quite well) one side
goes to soundcard signal side and other output goes to
XLR connector pins 2 and 3. Wire the pins 1 of XLR
connector with thick wire (at least 0.7 mm^2)
to the PC case to provide proper connector
grounding (you can out here "ground lift" connector
if you want).

If four XLR connector takes too much space, then
one option is the same transofrmer idea, but the
connectors are instead balanced 6.3 mm connectors.

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