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wiring mono/stereo devices into patchbay?

Postby stemwinder » Tue Aug 21, 2018 8:58 pm

hi there,

I have just bought my first patchbay (Samson S-Patch 48) and have a question. I want to wire in three mono/stereo limiters (2 FMC RNLAs and an Alesis Microlimiter). Each can be run as either mono (left channel only) or stereo.

Can these be wired into the patchbay such that they can be used in mono or stereo, without having to (un)plug any cables from the limiters?

I suspect the answer is no (does simply plugging a cable in the R channel means the device will automatically run in stereo?) - but thought I'd ask.

Thanks,

Darren
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Re: wiring mono/stereo devices into patchbay?

Postby Hugh Robjohns » Tue Aug 21, 2018 10:07 pm

The manual isn't as explicit as it could be with the internal wiring, but if its wired as I think it is, it should be possible to you use the patchbay as you want, albeit in a slightly unusual way.

The unusual aspect is that you need to select a vertical pair of sockets as the stereo inputs to the limiter (rather than horizontally adjacent sockets)... and select the half-normal (HN) mode for them on the corresponding toggle switch.

At the rear of the patchbay connect the top socket to the limiter's left input, and the lower socket to the right input.

When plugging up the limiter inputs on the patch bay, plugging a mono source into the front top socket should then feed both sides of the limiter with the same signal (via the normalling), while plugging left into the top and right into the bottom socket should access the two channels separately.

Give it a go and see if it works. I know it does on some forms of A-type patch bay (like the old signex I have here) , just not sure if it does on the Samson...
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Re: wiring mono/stereo devices into patchbay?

Postby stemwinder » Tue Aug 21, 2018 10:25 pm

thanks Hugh, the patchbay arrives in the next couple of days and I will let you know.

Another question - the RNLAs are unbalanced, and if you put a balanced cable into he input, it acts as both a send and return (allowing you to use one balanced cable for inserts as opposed to a Y cable).

I have done some Googling and it seems that I should be able to patch the RNLAs in with unbalanced cables and should only experience a drop in volume. Is that correct, or do I need special wiring (bal > unbal)?

Thanks again,

Darren
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Re: wiring mono/stereo devices into patchbay?

Postby resistorman » Wed Aug 22, 2018 2:29 pm

stemwinder wrote:thanks Hugh, the patchbay arrives in the next couple of days and I will let you know.

Another question - the RNLAs are unbalanced, and if you put a balanced cable into he input, it acts as both a send and return (allowing you to use one balanced cable for inserts as opposed to a Y cable).

I have done some Googling and it seems that I should be able to patch the RNLAs in with unbalanced cables and should only experience a drop in volume. Is that correct, or do I need special wiring (bal > unbal)?

Thanks again,

Darren

Not exactly... you would only get a drop in signal if you were going from balanced to unbalanced. But it will work fine with TS cables. TRS does not automatically mean a signal is balanced, it could also be a send/ return as it is in this case.

A crafty patch bay solution, Hugh :D
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Re: wiring mono/stereo devices into patchbay?

Postby Hugh Robjohns » Wed Aug 22, 2018 2:52 pm

stemwinder wrote:thanks Hugh, the patchbay arrives in the next couple of days and I will let you know.

Fingers crossed!

Another question - the RNLAs are unbalanced, and if you put a balanced cable into he input, it acts as both a send and return (allowing you to use one balanced cable for inserts as opposed to a Y cable).

Yes. Fairly common idea and makes plugging to a budget console's inserts much easier.

...it seems that I should be able to patch the RNLAs in with unbalanced cables and should only experience a drop in volume. Is that correct, or do I need special wiring (bal > unbal)?

Lots of options ... and potential bear traps... here.

You could use TRS cables to the patch bay for both your RNLAs and console inserts, allowing you to patch send and return with a single cable. You could even use the half-normalling function with console insert on the top row and effects send/return on the lower. No level loss that way and easy single-cord patching, but the potential for ground loop mayhem!

Alternatively, you could use Y-cables to separate the unbalanced send/return of the effects units and console inserts, and bring them into the patchbay in the usual way.

However, you then have potential problems not only of ground loops, but also of level losses if you patch between balanced and unbalanced sources/destinations.

There are ways around this kind of issue, either using specially wired cables or balun transformers, but the best solutions will vary with the specific equipment so you'll need to have a careful think about what you really want to patch to what, and how much patching flexibility you really need.

Combining balanced sources/destinations with unbalanced ones on the same patchbay is often quite problematic!

H
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Re: wiring mono/stereo devices into patchbay?

Postby James Perrett » Wed Aug 22, 2018 5:47 pm

Hugh Robjohns wrote:Combining balanced sources/destinations with unbalanced ones on the same patchbay is often quite problematic!

I've found that if you have a sensible grounding scheme and balanced outputs that are happy to have one side grounded then it usually works in my experience. I've only just discovered that the aux sends on my desk are unbalanced - I've been using them with balanced and unbalanced devices for many years with no problems.
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Re: wiring mono/stereo devices into patchbay?

Postby resistorman » Thu Aug 23, 2018 4:00 am

Since none of the equipment listed is actually balanced i/o, I don't see a problem here.
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Re: wiring mono/stereo devices into patchbay?

Postby stemwinder » Wed Aug 29, 2018 11:08 am

Hello again. Patchbay is here and wired up and, I think, everything is working okay! The rack does contain bal and non-bal hardware. Alongside the RNLAs (and the Alesis Nanocompressor - the Alesis Microlimiter was dead) it has 4 way Sytek pre (MPX4), SafeSound P1 pre, Golden Age Pre-73, DBX Project 1 EQ and the (beautiful) Slate Pro Audio Dragon (1176 clone).

I wired the compressors up as you suggested Hugh and, although the setup seemed to work (at the compressor), I was consistently losing an output channel regardless of where the output pair was patched. After a couple of hours of head scratching and testing it turned out that the 8 way unbalanced looms (x2, for the comps only) had multiple failures (despite being in good nick, and only a few years old).

The lesson here - check your looms BEFORE wiring up the patchbay!

The other odd thing was the EQ which worked if you patched it before the Dragon, but not after it. It turns out that the DBX needs a balanced cable on the way in, but an UNbalanced cable on the way out. Working fine now.

As ever - thanks for all your help SOS forums!

Darren
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Re: wiring mono/stereo devices into patchbay?

Postby Hugh Robjohns » Wed Aug 29, 2018 11:37 am

:thumbup: :D
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