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Weird MS Rig issue - Pics included


davidsonwilliam

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So, gearing up for some spring & summer gigs. (Yay, can't wait for winter to be over, right?)

I decided to tidy up my very basic MainStage rig, a rig I have been using for quite a while with no issues, until now, very oddly.

Rig is a Nord Electro 2, PreSonus AudioBox 2, and MacBookPro 13 Retina running fresh build of Yosemite(per this forum's sound advice) with spotlight off, wifi and bluetooth off, and everything else as lean as humanly possible. I stick with stock sounds, except for knock and session horns pro - and thats only on certain MainStage concerts. if I'm playing a basic rockabilly gig or something simple, I have a MS concert with only stock sounds. Then for bigger cover gigs I do like to rely on session horns pro as they sound as close as I feel I can get to a real horn section.

 

OK sorry for being long winded, here's the weird problem: I have had ZERO issues until I cleaned up my cables, wound them up and snugly but not too tightly zip tied them. I use a standard sturdy black keyboard stand, and I picked up a little 10" simmons electronic pad and tom-mount and mounted it to the back of the stand for a quick and easy - and sturdy mac stand. It works for me anyway.

Well, it had worked until i decided to clean house and zip tie the cables.

 

Now, 15-20 seconds into playing, even a basic piano patch - particularly as soon as I hit the sustain pedal (yes, a good clue, for sure) - everything locks up - and I mean locks up HARD. I have to reboot. I'm serious. Not running anything funky I swear. The only change was me cable tying everything and I included no power cords in my little exercise. Just audio, midi, usb, and well i think thats it really.

 

So, did i create some kind of goofy electro magnet interference thing with the coil there you can see on top of the AudioBox? I'm puzzled.

 

I'm going to undo this so see what happens of course. But I value this forum's input always, so if you've read this crazy rant so far, perhaps you'll have a moment to help me "myth-bust" this.

 

Please be gentle, I realize this question may make me seem really out there.

 

Thanks again,

Bill

 

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IMG_0492.jpg.5a9b0d32d5afb7adbbb5819614f14ecb.jpg

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From the pictures, It looks like a classic case of EMI (electromagnetic interference) between cables.

If you un-ziptie everything and it works fine, I would almost guarantee you're experiencing the magnetic field from one cable induced into one of your USB or midi cables. This will wreak havoc on that nice smooth stream of 1's and 0's your midi keyboard is sending to your computer. Even though you say you have no power cables running through there, audio cables carry AC and set up the same kind of magnetic field a power cord will. Furthermore, coiling up cables basically creates an antenna you attach to your ungrounded macbook. Are you using quality balanced audio cables? A quality cable will usually have a tightly braided outer shield and will reject/contain EMI much better than a cheeper cable with either a foil shield or some other less than ideal shield arrangement. I think if you cut the zip ties off you can use something like garbage twist ties to temporarily hold the wires where you want them while you test your rig. Try different configs until you get it right.

 

You can try a couple of things to resolve this.

 

1. Use shorter cables. We coil cables on stage to keep them neat. Anytime you're going to leave cables in place, buy or make cables as short as your needs allow.

 

2. Try not to bundle power, audio and data(USB or midi) cables together. Make separate coils, then separate those coils slightly from each other (like the olympic rings).

 

3. Try to arrange so that power and data cables cross perpendicular to each other rather than running parallel. I know this is easier said than done. You're obviously not going to have a big X grid pattern of cables running all over the stage floor, but when possible try avoid running cables for long distances together (this includes coiled).

 

4. Try using ferrite chokes on your USB cables. You can by these or harvest them from other cables that have them installed. They just clip on. Google "ferrite choke" if you're not sure what I'm referring to.

 

 

You're problem is a very old one that use to be a major problem. We don't run into it quite as much as the guys 50 or 60 years ago with most of today's cables but the electrical theory never changed over the years and the problem still lurks about the stage. Fortunately the fixes are usually cheep and simple.

 

Hope this helps!

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Hey Musicdan, thank you for that thoughtful reply! I so appreciate you taking the time. Well, as sort of expected, when un ties all the cables, the problem stopped. So weird, but maybe not as you say, it must have been creating some EMI, most likely the coiled area, but could have been the audio and midi close wrapped as I noticed I had those accidentally a little too tight.

 

But I think your advice sounded great so I got on good ol' amazon and ordered some nice shielded cables in short lengths, and also found a bunch of removable ferrite cores on old power cords in a box in the basement. There's no way I would have though of that - what a great idea, seriously, much appreciated. Not sure I'll need to, but after seeing that weirdness, I just don't want to take chances.

 

When the new short cables come, I am going to try to neatly bind everything with maybe small strip of gaffers tape instead of zip ties, and no more little coils of course.

 

Thanks again for the great suggestions and feedback!

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