wiring question

[hollywood_steve]

I need to fabricate a cable with a single XLR on one end and two XLRs on the other end. This is one of those weird stereo cables where the single XLR carries both Left and Right signals and the other two XLRs carry Left and Right respectively.

In other words, XLR(A) is wired:
Pin1=ground, Pin2=left, Pin3=right

my question concerns the other two XLRs.

XLR(#1) is wired:
Pin1=ground, Pin2=left, Pin3=?

XLR(#2) is wired:
Pin1=ground, Pin2=right, Pin3=?

My question concerns whether to tie Pin3 to ground or leave it open on Left and Right XLRs?

I had a similar cable for metering on my old Trident mixer, but I don't remember how it was wired. What's the best way to do this?

Thanks!

[Geoff_T]

Originally posted by hollywood_steve
I need to fabricate a cable with a single XLR on one end and two XLRs on the other end. This is one of those weird stereo cables where the single XLR carries both Left and Right signals and the other two XLRs carry Left and Right respectively.

In other words, XLR(A) is wired:
Pin1=ground, Pin2=left, Pin3=right

my question concerns the other two XLRs.

XLR(#1) is wired:
Pin1=ground, Pin2=left, Pin3=?

XLR(#2) is wired:
Pin1=ground, Pin2=right, Pin3=?

My question concerns whether to tie Pin3 to ground or leave it open on Left and Right XLRs?

I had a similar cable for metering on my old Trident mixer, but I don't remember how it was wired. What's the best way to do this?

Thanks!

Hi

I'd tie pin 1 and 3 together. The signal is unbalanced and is expecting to see a signal across pins 2 and 3.

[aurt]

Generally, I'd agree with Geoff and tie pin 3 to ground.
There is a case where I wouldn't, however. If the cable in question is taking two actively balanced (non transformer) outputs and putting them into one XLR as stereo, then I'd float pin 3 so that the low side isn't trying to drive a dead short. I have seen this cause problems in interesting ways, even in properly grounded facilities.

[Geoff_T]

Originally posted by aurt
Generally, I'd agree with Geoff and tie pin 3 to ground.
There is a case where I wouldn't, however. If the cable in question is taking two actively balanced (non transformer) outputs and putting them into one XLR as stereo, then I'd float pin 3 so that the low side isn't trying to drive a dead short. I have seen this cause problems in interesting ways, even in properly grounded facilities.

Hi

Yes, I was grinding my teeth as I posted my response... You won't find a vintage Neve with unbalanced outputs because of the risk of ground loops.

Transformers rule!

[hollywood_steve]

Just to explain the situation:


my new API 7800 has a feed for connecting external meters on the stereo bus. Unfortunately, they decided to put both the left and right signals on a single XLR, which then needs to be split out to a Left XLR and a Right XLR for connecting to my meters.

[Geoff_T]

Originally posted by hollywood_steve
Just to explain the situation:


my new API 7800 has a feed for connecting external meters on the stereo bus. Unfortunately, they decided to put both the left and right signals on a single XLR, which then needs to be split out to a Left XLR and a Right XLR for connecting to my meters.

Hi

Is the meter box one of your own build or an OEM model?

The signals must be unbalanced (two hots and a common) so it rather depends on how your meter box is wired.



PS I assume that your meters match the output's +4dBu = 0VU and that the 3600 ohm series resistor is in your box and not the API?

[aurt]

If your meters are wired with the coils between pins 2 and 3, then you'll have to short pin 3. I had been thinking that the cable was going the other way.

[hollywood_steve]

The meters are Dorrough 40-A2 combo peak+VU meters; the same model you find in about half the studios in the world.

[Geoff_T]

Originally posted by hollywood_steve
The meters are Dorrough 40-A2 combo peak+VU meters; the same model you find in about half the studios in the world.

Hi

Nice meters but I suspect the Sifam 22/32AF/AL range that Neve, SSL, etc., used better fits that title.

[Tim Farrant]

I would wire it with balanced cable as follows. By not connecting the sheild at both ends you will avoid earth loops.

Cheers
Tim

[Geoff_T]

Originally posted by The Buzz
I would wire it with balanced cable as follows. By not connecting the sheild at both ends you will avoid earth loops.

Cheers
Tim

Hi Tim

I totally concur with your sketch.

As a general hint, I think this thread could have been half the length if it had been posted what the cable was to be used for...

ie From what device's output to what device's input.

That would eliminate a lot of guesswork!