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Author Topic: wiring convention for stereo balanced lines on a Lemo plug..?  (Read 706 times)

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Offline andromedanwarmachine

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wiring convention for stereo balanced lines on a Lemo plug..?
« on: October 13, 2018, 06:02:35 AM »
Hello team,

(it's been a while!)

Just having a sort out on the 'rig, and i think i need to leave the 'theatre grade make-up proof' cables from my DPA's behind.

I currently have these two 'flesh coloured' spindly wires coming out of my Rycote basket, and it doesn't inspire confidence in handling (although it performs perfectly well).
I'm considering shortening the captive lines from the mics, and going into Lemo connectors, before making the jump from the basket on something more rugged, down to the recorder.

I type to enquire if there is a convention for single channel balanced lines in Lemo connectors (4-pin?) and furthermore if there is a convention for two channel balanced wiring also (6 / 8 pin?).

Obviously only three and six cores are required respectively, but I nod towards radio-mic conventions with the mention of the 4-pin..

Any opinions..?

Thanks

JimP
« Last Edit: October 13, 2018, 06:06:39 AM by andromedanwarmachine »
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Offline mjwin

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Re: wiring convention for stereo balanced lines on a Lemo plug..?
« Reply #1 on: October 13, 2018, 03:14:45 PM »
I think the standard here is that every radiomic manufacturer has their own!  Do you actually need 3 wires for each mic?  Lav mics (such as the DPA 4060/61) are unbalanced  & typically have only 2 wires: screen & signal/power. The microdot connectors are just that & you know where you are.  With multi-pin connectors (lemo 3,4&5 pin & TA5, etc.)  pro manufacturers each seem to have their own way of arranging the power for these mics - a more flexible version of "plug-in-power" if you like. This often involves added resistors etc. & there's sometimes a line-in option, too.  But you can see where this is going...  (Even the engineering "rule" that pin 1=ground isn't always followed in my experience!)

One general thing I'd say about LEMO 0B series connectors is that they're amazingly high quality, amazingly tiny and require amazing soldering skills to get a reliable connection! This notwithstanding, I like them:) Maybe in your scenario I'd go for Pin 1= left ground, pin 2=left signal, pin 3= right signal, pin 4= right ground. This gives each microphone wire its own pin but keeps the 2 ground wires next to each other,  which makes it easy if you use a 2 core + screen cable to your recorder/preamp/battery box. Of course, the cable you use depends mainly on your system configuration & the connector that end. It has to fit!

Another thought is that if you're using a Rycote basket, the handle will have an inbuilt clip for XLR connector or, if you use the stand bushing, there will be a little clamp for an XLR connector supplied along with it. The added size of the XLR probably won't be an issue & they are a lot easier to assemble with thicker cable.   3 pin & 5 pin are already standards for balanced audio with P48 power. If you want to avoid the possibility of someone inadvertently  plugging into a 48V mic input, you could use the 4 pin variant with pinout as for the LEMO above. (Ok. so 4 pin XLR is sometimes used for power connections, but it's much less common than the other types.)


Offline andromedanwarmachine

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Re: wiring convention for stereo balanced lines on a Lemo plug..?
« Reply #2 on: October 13, 2018, 06:02:33 PM »
Thanks MJwin,

yes- you are absolutely right; my DPA's are single-ended, and do not require balanced connectivity (not sure what I was thinking of there?!)
I have seen a bit of 4-pin XLR power wiring before; plus they are used as cue-lights in the theatre industry; so I'm keen to avoid that format.

Yeah- I did see some of that crazy powering & bias setup stuff in some 4-pin Lemo formats; there didn't seem to be standard.

It would certainly be worth taking advantage of the XLR shaped recess in the handle of the Rycote; yes. What I haven't explained is that the DPAs I have, came wired to minjacks- and one reason for this work; is to get those things out of the equation.
I've got 25 years professional soldering experience, so I reckon I can handle the Lemos.
(in fact; I've actually got a crimping tool for them somewhere?) Which is a bit weird.
Having said that- I've never made off Lemos yet myself!- maybe I need to get hold of some to make a judgement.

My recorder has separate XLR inputs and I suppose I'm looking at;

2x XLR 3M (which house my Church pre-amps) to 1x XLR 5F, as a cable. (which is a convention)

And then an XLR 5M to 2x Lemo 0B (of some kind), as a cable

and then the opposite Lemo 0B to the DPAs (which would happen inside the basket, maybe) replacing the cursed minijacks


Thanks for your feedback MJ; that's been very thought provoking and helped me pull focus on the task

Phillips N2233 "full auto shutoff"> Aiwa HSF-150 (x2)> Sony WM-D6C (x2)> Sony TCD-D3> Sony MZ-R3> Marantz PMD-650> Sony MZ-RH1> HHB Portadisc> Macbook 13"& M-box 2 +ProTools 8! and now Nagra LB!

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Offline mjwin

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Re: wiring convention for stereo balanced lines on a Lemo plug..?
« Reply #3 on: October 14, 2018, 04:58:56 PM »
Thanks for your feedback MJ; that's been very thought provoking and helped me pull focus on the task

If you're used to soldering small stuff, you'll be fine with the LEMOs :bigsmile:

Now, not wishing to defocus you, but just to add a few practical details:

Firstly, I see that I mistakenly mentioned "LEMO 0B" size connectors.  Just to avoid confusion, I meant to have said that the ones used by Zaxcom, Sennheiser, (Shure?) for radio-mics are actually the "00" size screw-on, with 3 or 4 pins & internal links. These are probably more suitable for hanging onto the fragile cables of your DPAs.  Just to add to the confusion, I just looked up the Lectrosonics circuit & they  use a TA5 plug &, again,  internal links are required to get the powering correct. It's another option, cheaper & a bit easier to assemble.

But without looking up & comparing all of the manufacturers' specs, I can't say for certain whether any of them are directly interchangeable, even if they use the same connector.  I think it's part of tying you into their system!  So if you're likely to ever want to use your mics with a bodypack transmitter, you probably need to decide which brand and model you might use & go from there.

But back to LEMOs
Depending on your supplier & how you buy the connectors, you'll probably have a limited choice.  But the part numbering system allows you to specify every last detail.

In case you haven't got it, here's a useful pdf with great internal links to the appropriate sections to help you compile the part number:

https://www.lemo.com/catalog/ROW/UK_English/unipole_multipole.pdf

I actually prefer the push/pull latching arrangement to the screw-on variety, and with 2 pins, you know where you are. So for the plug on each of the DPA leads, I'd suggest:

FGG.00.302.CLAD.22.Z
That's: push/pull plug size 00, chromed brass shell, 2 pin male, solder connection, 1.4-2.2mm cable collet, strain relief backnut.
The rubber strain relief boot will be:
GMA.00.------ (you'll have to select the options)

Then you'll need the matching sockets & cables to go to your 5pin XLR.

Mogami 3031 mini balanced cable is probably a good choice as it has a tough braided* screen  & is about 3mm overall dia. I've used Belden 1804A mini starquad, which is a similar size but 4 core & overkill for an unbalanced connection, (but I have a length of it bought years ago for something...). Each pin (signal & ground) can then have its own wire & the screen is separate & connected only to the shells & finally grounded at the preamp (or in your 5 pin XLR).  One of the minor quirks of the LEMOs is that there's no separate terminal for the screen. The trick is to fold a short length of the braid back on itself so that it's on the outside of the cable sheath, (a bit like turning down the cuff of an overly long rubber glove), then push the whole lot into the clamping collet before tightening down.  This means that the collet needs to be of a slightly larger diameter than the nominal cable sheath.  Having a few spare collets of differing sizes doesn't hurt...

Ahh... The quirks of LEMOS.   But, overall,  they're very well thought out connectors: they just impose a bit of rigour on the assembly process!

* I'm sounding like a cable geek here, but the real advantage of braided screen over spiral lapped is that if you tug on the cable (which happens) it tightens on the inner cores and hangs together. A lap screen cable tends to stretch & twist as the spiral wants to unwind. This causes kinks in the cable & also puts stress on the tiny internal wires.

Phew!

Now you know why these pro radiomics cost so much - it's the hours that go into choosing the connectors! (then the time taken to wire them, & not forgetting the cost of the LEMOs themselves...)

Good luck with it all:)

Martin

Offline andromedanwarmachine

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Re: wiring convention for stereo balanced lines on a Lemo plug..?
« Reply #4 on: October 22, 2018, 09:38:21 AM »
hmm!

MORE for for thought- thank you again for going into detail over this, Martin-

I'll have to try and soak it up and make an informed judgement.

JimP

Phillips N2233 "full auto shutoff"> Aiwa HSF-150 (x2)> Sony WM-D6C (x2)> Sony TCD-D3> Sony MZ-R3> Marantz PMD-650> Sony MZ-RH1> HHB Portadisc> Macbook 13"& M-box 2 +ProTools 8! and now Nagra LB!

http://soundcloud.com/andromedanwarmachine
http://soundcloud.com/bells-of-scotland
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