Mosses and Mitchell 56 pin EDAC pinout?

[gareth33]

Hi there all...

I'm looking for some help with wiring a Mosses and Mitchell GPO patchbay. I have a 3u 96 point patch bay, 24 per row with 4 x EDAC 56 pin connectors on the rear, I assume one per row. The patchbay is half normalled.

My plan is to run the first two rows, 24 jacks to my 24 mixer out's to 24 A/D converters in (half normalled)
Rows 3 & 4 - 24 channels A/D out to mixer tape in


I've been looking for information regarding the pinout for these connectors but haven't really found it. There is one per row and 24 jacks, so I assume that the connector is wired for 24 channels of audio? I want to wire a loom going to 24 x 1/4" mono jacks from the patch bay, and obviously four of these in total, going to my 24 track mixer and converters etc.

Hoping this is the right place to post this, I'd be very grateful for any advice on the subject. Many thanks

Gareth

 

[pucho812]

The math does not add up to 96 channels. Unless there is shared grounds or something else going on.  I am sure there is information on the Mosses and Mitchell website. If not, then you can continuity test which although will take time will help you find the pin out.  I suspect you may have some patch points that are mults.

 

[MagnetoSound]

I have the same units. The EDACs (they are indeed 56-way) are wired for 24 twisted pairs and a common screen which connects to a ground bus in the jackfield (one per row), ie each jack has tip and ring wired to two of the EDAC pins and the screen contacts are all bussed together and brought out to the green binding post on the rear panel as well as two or three pins in the EDAC connector.

This is a typically quirky UK broadcast spec, clearly designed to save cost on both cable and connectors, but which actually performs without any reduction in signal quality or isolation, provided that all lines are balanced (and, preferably, that all signal grounds are connected to a a clean technical earth).

Your cables are apparently unbalanced (if terminating in mono jacks), so crosstalk might be compromised, but you will only know by trial.

I don't have a pinout to hand, but if you pop the lid of the box you will see that all rows share the same wiring pattern and it is quite easy to ascertain the pattern on row 1 by buzzing the pins through to each jack for continuity.

Hope this helps.

 

[gareth33]

Thank you both for your replies, they are a great help. This is the first time I am wiring a patch bay, it's for my home studio.

I have a couple more questions as I seek to understand this, what do you mean by twisted pairs exactly? I need to double check and look at the balanced versus non-balanced situation, as obviously my Fireface has balanced connections, my Soundtracs Topaz, I'm not sure off the top of my head.

My intention was to wire these up, one jack per channel, line in or tape out etc etc. So that would require one jack per patch point. I was under the impression that 56 pin EDAC didn't add up to 24 individual channels of balanced audio, or maybe they do or I could adapt these to my needs?

I will be wiring the looms myself and am not adverse to stripping out the EDAC's and just soldering direct to the frames in the patch bay, assuming that they are essentially the standard sort of long frame inside with solder points? I don't have them here yet to open so I am not sure.

Looking for info on the net I'm not finding much, though I have seen it listed as 'continuous' which I assume means all the jacks are half normalled to each other. I only want individual pairs half normalled to each other not all 4 rows. Is this something I could work around as well? I hope I have explained myself well enough.

Any advice is appreciated, I am still learning a lot about studio wiring and still not clear on everything.

Gareth

 

[pucho812]

Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. It was invented by Alexander Graham Bell.


So in this case the twisted pair is the hot and cold of a balanced signal and all the shields tie together at a central point.

 

[keefaz]

My intention was to wire these up, one jack per channel, line in or tape out etc etc. So that would require one jack per patch point. I was under the impression that 56 pin EDAC didn't add up to 24 individual channels of balanced audio, or maybe they do or I could adapt these to my needs?

I will be wiring the looms myself and am not adverse to stripping out the EDAC's and just soldering direct to the frames in the patch bay, assuming that they are essentially the standard sort of long frame inside with solder points? I don't have them here yet to open so I am not sure.

Looking for info on the net I'm not finding much, though I have seen it listed as 'continuous' which I assume means all the jacks are half normalled to each other. I only want individual pairs half normalled to each other not all 4 rows. Is this something I could work around as well? I hope I have explained myself well enough.

Any advice is appreciated, I am still learning a lot about studio wiring and still not clear on everything.

Gareth

I have the same model as well. I removed the Edacs, installed 25 way D-SUBs and a bunch of XLRs on rear pannel. I redid all connections, made some mults and added half normaled wires only where I wanted to. I haven't taken pics of my mods yet

 

[MagnetoSound]

The EDACs have 48 pins used for audio (24 x hot and cold), and 3 or 4 are used in parallel for shield continuity. Just pop the lid and you'll see what I mean.

Rows are half-normalled in top/bottom pairs (A-B ... C-D ... etc).

 

[keefaz]

Pic of my mod...

 

[gareth33]

Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference

Right, of course,  : the pin out is making more sense now, I just kept finding contradictory information everywhere I looked.

Thanks for all the replies, I'm especially pleased to see your mods Keefaz, thank you, great wiring by the way. I will likely go this route myself and skip the EDAC's. This opens up a whole other question for me, which is grounding within a patchbay system. Especially as part of my set up is unbalanced, synths and effects units. Though the first 4 rows will be balanced going from the mixer outs and A/D in's etc.

I'm going to read up on grounding schemes, but I assume at this point on the unbalanced sections I'll just tie the ring and shield together.

Thanks again.

Gareth

 

[keefaz]

Thanks for all the replies, I'm especially pleased to see your mods Keefaz, thank you, great wiring by the way. I will likely go this route myself and skip the EDAC's. This opens up a whole other question for me, which is grounding within a patchbay system. Especially as part of my set up is unbalanced, synths and effects units. Though the first 4 rows will be balanced going from the mixer outs and A/D in's etc.

I skiped the EDACs when I realized that 10 x D-SUB chassis + 10 x D-SUB metal cable + 16 chassis XLRs connectors would cost less than just 1 or 2 x 56w EDAC + pins...

If you redo the connections, maybe reserve an unbalanced section on the patchbay and use shielded cable for this section

 

[gareth33]

I'm going to jump on the back of this thread rather than start a new one. In the end I bought some 3 row MM B gauge jackfields and am adapting/wiring them myself. 

I have my patch bay wiring pretty much sorted out in my head now, but I have come to the part where I need to address the reality of balanced and unbalanced systems together. I've read quite a few of the threads around here but I am still not entirely sure of the best practice for my set up.

I am half normalling the majority of my connections for example, balanced DAW out - balanced mixer (soundtrack topaz) Tape in. So for this I am going to use TRS from both ways to the MM B gauge patch bay I have connecting the shield on the ground lug per jack.

The next row down will be my synth outs to patch bay. So at this point I have either the option to connect my mono instrument cable to the tip and sleeve (sleeve being the shield) on the patchbay and to leave the ground lug with nothing. Or to wire a paired cable connecting the shield to cold at the instrument and opening up to shield on the ground lug at patch bay Tip and Ring = hot and cold as per normal.

This is how I deal with for example, mixer unbalanced outs to monitor balanced in's. Join shield and cold at the mixer out and spread them at the XLR end. It works for me with no noise or hum.

I was planning on doing the same for the FX out's and in's. Either wire up the patch bay with nothing on the ground lug (I hope that bit is clear, by that I mean the ring on each jack for the ground wire) so, just Tip = hot ring = cold or cold/shield together. Most of my effects are unbalanced with the exception of the Eventide Orville.

Hope this makes sense, any tips are much appreciated...

Gareth

 

[keefaz]

I was planning on doing the same for the FX out's and in's. Either wire up the patch bay with nothing on the ground lug (I hope that bit is clear, by that I mean the ring on each jack for the ground wire) so, just Tip = hot ring = cold or cold/shield together. Most of my effects are unbalanced with the exception of the Eventide Orville.

Hope this makes sense, any tips are much appreciated...

Gareth

Seems like a good plan. Watch for patchbay inputs though, try to not connect ring + shield here, because if you patch an unit who has balanced outputs like fig 5b at:
http://www.douglas-self.com/ampins/balanced/balanced.htm
... in patchbay input jack who has ring + shield connected, that will loads heavily the cold side of the unit balanced outputs (which may cause distorsion). Or maybe just disconnect ground on patchbay output jacks for this sort of outputs, I don't know the more benefical way