This is driving me crazy!!! Somebody please help.

[in10shun]

This problem doesn't directly involve my Digi 001, but it's affecting my whole little set-up, so my 001 is hurting anyway. I'm pretty sure I've got some kind of ground loop or electrical interference somewhere among my equipment. I really know nothing about this so if I make any stupid assumptions please forgive me.

I'm using a Behringer PX 2000 Balanced Patch Bay to connect all the ins and outs of my studio. All of the channels are set to the "open" position, meaning that signal flow enters the back top row, exits the front top row, re-enters the front bottom row, and finally exits the bottom back row.

The first 12 points are dedicated to the mixer outs (Mackie 1604-VLZ) and Digi 001 ins. Points 13-24 are set up as follows:

Back top 13-14 are stereo out from a CD player. Back top 15-16 are stereo out from a tape deck. Back top 17-18 are stereo out from my PC soundcard. Back bottom 13-14 run out to channels 13-14 on the mixer. 13 is panned left and 14 panned right. I can patch the outs from any of the equipment to front bottom 13-14 and send it to the Mackie. This allows me to hook up all the stereo equipment and only use up two channels on the board.

The problem is that after 20 minutes or so of playing a CD or whatever is hooked up at the time, either the left or right channel/output (whatever the problem is) starts to crackle and hiss as if there was a loose wire or bad connection somewhere. What's interesting is that it's always the left OR right, never both.

I took everything apart and tested every in and out of every piece of gear and the mixer, as well as every cable. Everything works fine when run independantly. So what gives?

My thoeries (far-fetched as they may seem) are these:
1) The outs of the stereo equipment are unbalanced, once they hit they patched cables, everything becomes balanced, so maybe that's causing a problem? I doubt it though because this would make a problem occur right away and this occurance is totally random.

2) I've got everything racked in an 8-space SKB case, is there some kind of grounding problem there?

3) I have my telephone run throught the modem in my PC and plugged into the Furman power conditioner with everything else. Would that cause random interference?

4) My equipment is cursed and it's a sign that I should give up this recording stuff.

Any thoughts and/or suggestions would be greatly appreciated. Thanks.

James

[oslpchris]

Sounds pretty frustrating... what kind of a power amp are you using? You say this only happens after about 20 minutes of use? never right away?? Sounds like a power amp deal to me... maybe like there is a loose connection and when the system heats up the connection breaksdown??

That's my novice opinion... Hopefully one of the smart people in this forum can help out. Have you gone through the whole thing taking out one addition at a time? Sounds like a pretty tough thing to troubleshoot... especially since it takes a while before the problem starts. good luck

chris

[kcarter]

I know how frustrating a problem like this can be. Take a deep breath, clear your head, get a cup of tea (or whatever) and commit a block of time to troubleshooting the problem. (Let me get my tea too ... ok, let's go!)

First off, get the system set-up where it is causing this problem. (In your case maybe you should start the system first, THEN brew the tea [img]images/icons/smile.gif[/img] )

Now lets try to pin-point the source of the problem. Is it in your speakers only? What about headphones? If you cross your patch cables, does the problem swap sides or not? What about moving the offending channel to a different jack on the patch bay. This kind of isolation will help you find the offending piece rather quickly (hopefully). Granted the symptoms seem very strange, but only by systematically tracing down the culprit can you discover the "oops" or "ah-crap" or whatever the cause is.

Work your way through the entire chain, from the source machine all the way to your power amp. Each time crossing the cables. If you start at the source, presumably the problem won't swap sides. Keep going until the problem DOES swap sides. The unit just before the last swap is the one giving you the grief.

Forgive me if this seems too simplistic, but it is the approach I'd follow if the problem were mine. Good luck, let us know how it goes.

Kurt

[in10shun]

OK, I've gone through the process of testing every piece of equipment in the chain. One note, there is no power amp involved, I have a pair of Roland DS-90A powered monitors. However, the problem is not with them, it seems to lie in the patch bay. The signal out of the CD player (and other devices) is fine. If I wire the CD Outs diretly into the mixer Ins everything works fine. But when I've got all the gear running through the patch bay, the interference occurs. So basically the signal gets messed up somewhere in the patch bay on it's way to the mixer ins.

The problem here is that there are now now 8 1/4-inch plugs involved in the chain. The orignal stereo signal runs into the Back Top, proceeds out the Front Top and is patched into the Front Bottom. It then travels out the Back Bottom and into the mixer.

So who knows about patch bays enough to intelligently analyze this? Not me that's for sure. Anyone with info please help, I'm pretty much stumped.

Thanks,
James

[kcarter]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by in10shun:
The problem here is that there are now now 8 1/4-inch plugs involved in the chain...So who knows about patch bays enough to intelligently analyze this? Not me that's for sure.<HR></BLOCKQUOTE>
My immediate assumption is that both the patch bay and patch cables are old/used. I've had lots of problems over the years with dirty contacts on 1/4-inch plugs and jacks. They don't even have to look dirty. Unfortunately I haven't found a good spray cleaner that works well. For starters, try new cables (with NEW plugs on them). If money isn't an object (Hah!) go for the gold-plated ones. Maybe the actual jacks of the patch bay aren't so bad. But if they are, disassembly and mechanical rubbing with a MILD abrasive might be in order -- not a pleasant thought.
Kurt