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mikebarber

DIY TC cable (5pin LEMO to DIN 1.0/2.3) grounding question

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i'm about to put together a bunch of TC cables, and was wondering about ground. for example, the TC LEMO 5-pin pinout from the SD633 is:

 

1 = ground

2 = SMPTE TC in

3 = ASCII in/out

4 = tuning out

5 = SMPTE TC out

 

so, using a single conductor cable, i'll connect LEMO pin 5 to the DIN conductor pin for my uni-directional cable for feeding TC from my SD633 to UltraSync One.

but i'm wondering if it's necessary (or at least wise/best practice) to connect LEMO pin 1 to the cable shield for grounding? or is that totally unnecessary?

 

 

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hmmm, i made the cable last night before i saw the additional replies saying i do need to. fwiw, the cable works just fine without it, and appears that it's in fact not necessary. whether or not it's best practice is a different matter, but it works just fine without it.

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eeh, measure the resistance between pin 1 and shield on the device.
It should read zero, meaning, if you jack in the plug, it is connected.
How hard is this?

(Or I'm missing something...)

 

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And sorry, I thought the question involved attaching the shield to the connector shell.

 

But you can't send any signal, balanced or not, on one wire. Pin 1 and Pin 5 on the Lemo to lo and hi on whatever connector feeds the Ultra Sync.  Looks like an SMC? Gad, a different connector for TC.  Ugh!  Looks like the perfect application for my Camlock-to-SMC (TM) adapter.

 

D.

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20 hours ago, tourtelot said:

And sorry, I thought the question involved attaching the shield to the connector shell.

that's a correct assumption, as the cable shield is mechanically connected on both the LEMO and DIN 1.0/2.3 via crimping.

 

following the connector manufacturers' assembly instructions, and connecting LEMO pin 5 to the DIN conductor pin, i have exactly what i need for a uni-directional TC cable from the SD633 to UltraSync One. it worked perfectly in my testing and in the field over the weekend, so it's safe to say that it is NOT required to involve the LEMO's ground pin.

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That assumes that chassis ground and electronic ground are strapped together.  Sometimes that is true and sometimes the two grounds are not connected and if Pin 1 on the Lemo is not connected, the cable will not work.  I would always connect Pin 1 on the low side but see no need to connect the low side (shield probably) to the Lemo shell.  In fact, in some situations, that would open the path for a ground loop and increase the possibility for putting T/C audio into your primary audio path.

 

D.

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1 hour ago, tourtelot said:

That assumes that chassis ground and electronic ground are strapped together.  Sometimes that is true and sometimes the two grounds are not connected and if Pin 1 on the Lemo is not connected, the cable will not work.  I would always connect Pin 1 on the low side but see no need to connect the low side (shield probably) to the Lemo shell.  In fact, in some situations, that would open the path for a ground loop and increase the possibility for putting T/C audio into your primary audio path.

 

D.

 

Doug is correct on this...... 

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