Balanced/Unbalanced patchbay questions

flyingace

flyingace

Active member
So, I started this thread thinking there was something wrong with my newly repaired ART MPA II preamp but it turns out it that its a patchbay issue.

I'd really like to have this connected via patchbay to my console. I have had it connected via XLR out to 1/4" TS (unbalanced) in to patchbay and using unbalanced patch cables to carry the signal to a channel via patchbay.

It works when I plug it direct from the back of the MPA using the unbalanced out but there is no unbalanced IN on the MPA, unfortunately. So, what is my best course of action:
Have it connected to a balanced patchbay and patch cable it using balanced patch cables to an unbalanced patchbay channel strip? would this work?

Thanks, I've been around a lot of this for years but this is my first foray into trying to have everything patched from the back for quick and easy use of all gear in my studio. It's a dream but it's also complicated and a hassle!
 
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Your patchbay - is it hardwired or does it have 3 circuit jacks at the rear? There should not be a problem - First thing. Is the patchbay a balanced or unbalanced one? Mine are all 3 circuit balanced - so I would take the XLR to a 3 circuit, balanced jack and stuff it into the rear of the patchbay. That pair of sockets on the patchbay can be balanced and with a 3 circuit patch cable, patch to anything. If the 'anything' is an unbalanced device then the patchbay will automatically unbalance when an output has a 2 circuit jack (or shorted 3 circuit jack) in the back. Patchbays just cope with rings shorted to sleeve. If it's an unbalanced patchbay, then every input will have ring and sleeve shorted - and the same with outputs. Any balanced device works perfectly well with being unbalancd by linking ring and sleev or XLR pin 1 to 3. The only problems occur when wiring is inconsistent. Like XLR unbalancing by linking 1 and 2. This works fine, but with a patchbay there is the possibility of double unbalancing - where XLR 1 gets connected to pin 3 at one end of the chain, but then linked to pin 2 somewhere else, which totally silences it. If you buy a patchbay, but a balanced one, and use balanced patch cables. If the in or output devices are unbalanced, it doesn't matter. This way, it defaults to balanced wherever it can.
 
I have a pair of these...https://www.sparkfun.com/products/14003 balancing the unbal output of a S/PDIF converter to a mixer. There is also a balanced in to UnBal out module.

You can always 'impedance balance'* an output but inputs either need electronics or a transformer and those are expensive for good ones and even then not quite as transparent as a good op amp.

*Assuming you can find out the output resistance but if not 100 Ohms is usually a close guess.

Dave.
 
Balanced patch bay did the trick! The DBX is a nice unit for the money and I’m thinking about replacing all my old ProCo patch bays with them. Some of the plugs on my ProCo ones are getting loose and a real pain. Thanks all for the advice!
 
@flyingace I don't really understand. Are you exposing the outputs of the MPA, the inputs, or both via the patchbay? If the inputs, that's interesting since they're mic-level and they pass phantom power.
 
You know, that’s a really good point! I’ll never plug anything into those rear inputs except mics and my main reason for wanting to use the MPA is for condenser mics, so I think I’ll disconnect inputs from patchbay, put some pigtails on it coming out of my console that I can easily plug a condenser mic when needed, then output it to a line input channel in my console, then I can use my snd/rcv to add compression or other effects, etc.
Thanks for the perspective!
 
flyingace said:
You know, that’s a really good point! I’ll never plug anything into those rear inputs except mics and my main reason for wanting to use the MPA is for condenser mics, so I think I’ll disconnect inputs from patchbay, put some pigtails on it coming out of my console that I can easily plug a condenser mic when needed, then output it to a line input channel in my console, then I can use my snd/rcv to add compression or other effects, etc.
Thanks for the perspective!
Click to expand...
If by "pigtails" friend you mean XLR to XLR M2F adapters then,.. good idea on another front. They can also be called "sacrificial" adapters. These are often used on very expensive equipment when replacing a damaged socket would be expensive and/or cause unwanted 'down time'. I made a set up for both XLR and jacks for an AP audio test set.

Most interfaces are not of course anything like as expensive as an AP rig but a buggered socket can still be a pain and a waste of time and money.

If there is a spare 'IU' on a rack you can get pre punched XLR plates for a quite reasonable sum as well.

Dave.
 
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