Is there such a thing as a custom cable that connects balanced and unbalanced gear?

  • Thread starter Thread starter Chris F
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Chris F

Chris F

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Obviously, the best thing to do is to make sure that you always connect balanced to balanced and unbalanced to unbalanced, or you're going to get a nasty ground loop complete with annoying hum. But if you really wanted to connect a piece of balanced studio gear to an unbalanced live rig, how would you go about it? If the answer is a special cable, can you buy them premade?

Thanks in advance.
 
If the gear in question is electronically balanced, then you don't need any special cable - in many cases you simply wire them together with an unbalanced cable and the connections at the balanced gear end will adjust. You will get a 6dB drop in signal level though....

If the gear is not electronically balanced, the ideal way is to use a high-quality transformer to unbalance the signal. Radio Labs makes them, and so does Ebtech.... I've used the Ebtech and it doesn't seem to affect the signal a whole lot.
 
Thanks for the reply. The thing I've noticed so far is that the moment I try to connect an unbalanced piece of live gear (in my case, a Raven Labs PMB-1) to a balanced piece of gear, I immediately get ground hum in the output of the unbalanced gear whether the balanced gear is even turned on or not. Would the transformer take care of this? If so, where do I find the ones you mentioned, and how much do they cost?

I've always heard these kinds of "ground loop" issues described as some kind of voodoo called a "Pin 1 problem". I take this to mean that the tip of a TRS plug and the tip of a 1/4" unbalanced patch cable are not supposed to be connected to the same thing, but - as always - I could be wrong.
 
There's a page at the Jensen Transformers site that shows you how to build the adapter cable in 3 different versions from "works OK" to "best way." I have it at work and can send it tomorrow if you like.

DD
 
DigitalDon said:
There's a page at the Jensen Transformers site that shows you how to build the adapter cable in 3 different versions from "works OK" to "best way." I have it at work and can send it tomorrow if you like.

DD
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Thanks, I'd be most grateful. I may get one of the Ebtech units anyway, since I'm sure this is not the only time this will come up. Looking at the unit, I can't figure out if it's capable of running two connections to the same unit, i.e. - unbal/out to bal/in, then bal/out to unbal/in. Also the same company makes a unit called a "Line Shifter" which corrects the line levels of this same type of connection. I'm not sure if it also fulfills the same function as the unit that Blue Bear linked.

But I think I'm handy enough with a soldering iron to be able to put together a couple of cables....and since this stuff is going to be wired into a 3 space live gig rig for some time to come, I'll be happy just getting it done anyway I can and getting on with life. At the moment, I'm playing with the balanced gear basically ungrounded, which makes me nervous.
 
There are unbalanced XLR cables out there, but you have to be REALLY REALLY careful into what you plug them into (i.e. a mixer with phantom power :) Most mixers don't like shorting +48V to ground...).

The unbalanced XLR connectors should look the same as regular XLR cables.. but I'd recommend labelling them so you don't make a smokey mistake somewhere down the line :)
 
The Raven sould NOT be giving you that kind of noise. (Are you doing an insert or something?) Why not call the company and see if they have any good ideas?
 
Treeline said:
The Raven sould NOT be giving you that kind of noise. (Are you doing an insert or something?) Why not call the company and see if they have any good ideas?
Click to expand...


The Raven Labs unit isn't giving me noise - it's the connection between the (unbalanced) Raven Labs blender and the (balanced) EQ that is noisy. Both units, when connected to the proper type of gear, are extremely quiet.


Digital Don - Yikes! :eek: I downloaded two of those pages, and it looks like I'd have to be wiring capacitors into the cables themselves! If this is the case, wouldn't I just be better off with one of the Ebtech units?
 
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