ANother Wiring issue.

B

blazingstrings

dgatwood can **** himself
Hey again!

I need to wire the Unbalanced 1/4" direct outs of my Fostex 812 mixer to a Balanced patchbay and then or to a M-Audio Delta 44's balanced ins.

I was looking at this http://www.vandenhul.com/artpap/wiring19.htm and the http://www.rane.com/note110.html diagram 14 which is the same way.

Is it ok to not hook the sleave to ground?
Is this comon?

Sorry for some many wiring questions. Most of the stuff I have wired was simpler than this stuff I have now.

Thanks in advance.

-Blaze
 
There is no point in doing so, you won't achive any added resitance to noise, a unbalanced 1/4'' to an unbalanced 1/4'' will do the same for you, just make sure it's sheilded.



I think.


-jeffrey
 
the only time you should not hook up the shield is in a ground lift situation. Or if you are telescoping the ground between two amps. you should try to get a multichannel DI in between the D-outs and the P-bay. summing the t+r on the D out end will work but you will be dealing with an impedence issue. and depending on what gear you are interfacing with the patchbay may cause problems with differnt makes of gear as to how they will respond to the unbalanced signal.
 
Thanks Peter.
Hmmm this is getting interesting............. And I mean that in a fustrating way. :confused:

Basicly the reason I'm putting the outs to a patchbay is so I can switch what the direct outs are going to such as all eight to a Delta 1010(future upgrade) or if I want to send just four or two chanels d-outs to another machines card(audiophile or delta 44).

I suppose just wiring them to the patch bay un-balanced and then setting up all the cards for un-balanced consumer level would work just as well........
Considering that I have been pluging unbalanced multi FX for a guitar directly into the card with no issues.........

Would that work? I mean I'm not plugging the direct outs into anything but the sound cards ever.....

Much Input is welcome.

-Blaze
 
The Rane note fig. 14 is correct; this puts the ground of your UNbalanced output as the LOW side of a balanced input, the hot of your unbalanced output as the HIGH side of a balanced input, and ties the GROUND of the balanced signal ONLY to ONE END of the shield - this allows the balanced input to see the full signal of the unbalanced output, and also makes it so there is NO WAY any current can flow in the shield.

This is good, because what causes hum in interconnects is CURRENT flowing in shields and grounds. By using a "telescoping" shield (only one end connected to a chassis ground) this puts the shield at GROUND potential for best noise immunity, but does NOT allow the possibility of any current flow except in the signal leads, both of which are running inside a STATIC (no possible current flow) shield.

You ALWAYS want the shield of any cable connected to ground, but any current in that shield (due to difference of potential between chassis points) will cause the shield to CAUSE hum instead of eliminate it. So, whether you have balanced OR unbalanced wiring (or are converting one to the other as in this case) it may be necessary to eliminate ONE, but not BOTH, ends of the ground connection for the shield.

Bottom line - the Rane diagram is correct and will work best. However, don't EVER wire things so any chassis in the system has NO ground at all; this is asking for death... Steve
 
Sweet!

I've been looking for those diagrams forever! I had them somewhere but couldn't find them. Thanks for posting it!
 
Hey knightfly,
I have been dealing with a ground loop....... How do you eliminate it?
By disconecting the ground at one end then?
Is that mostly ok?

I'm also dealing with this in a patchbay too......

Thanks for any help!

-Blaze
 
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More info than I'd have time to type (it's nearly 3am here)

http://www.rane.com/note151.html

IIRC, they recommend building a "test" cable or two - with a way to disconnect the shield at one end. You replace one cable at a time (or two - stereo) and disconnect the shield from ground at one end - if it makes the noise level LESS, you build a replacement the same way, and move on to the next cable. IF you have more than 2 pieces of gear, realize that this isn't a "between coffee breaks" project :=(

You'll need some sort of AC voltmeter to place across the output of your system, and a way of noting just exactly what the noise level is at each point in the test, but it's about the only way to get things as quiet as the can be. Just don't do TWO changes at once, and assume you know what made things better... Steve
 
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