[RAILhead]

I have a 1/8 stereo male that I want to split into left and right channel XLRs. I'm doing this to send audio from my computer to my subwoofer, then on to my studio monitors. I had Mark Stoddard at Lavacable build me one, but it's not working -- and he's already tried to fix it once.

With his cable, I can pan left and right and get audio, but when I move the balance to center, I get just garbled, odd audio. I'm thinking phase inversion...?

Further, my multimeter is showing signal from the tip of the 1/8 to BOTH XLRs, and it's also showing signal from the ring to BOTH XLRs. Shouldn't it be one or the other?

All that said, how should this cable be wired? I can see how to wire the tip and ring to the left/right XLR, as well as a common ground -- but I don't know what to do with the XLR return.

Anyone have a diagram they can post or draw for me?

[Doofy]

Radial Engineering - JPC Computer / A/V Direct Box

(Going unbalanced to balanced is a serious headache otherwise)

[RAILhead]

No, I can't do that. I have a piece of crap Hosa that's going 1/8 stereo to left and right 1/4, and it works — but it's a piece of crap. My sub supports XLR, too, so that's what I want to go with.

I'm thinking there's some kind of phase inversion going on...

[Doofy]

Originally Posted by RAILhead 

I'm thinking there's some kind of phase inversion going on...

Yes. There's gonna be, because that's the point of XLRs - positive phase on the hot, negative phase on the cold. Unless you can find a way to feed those cold pins with an inverted phase signal from the hot, there's probably going to be problems.

Essentially:
Sleeve -> ground.
Tip -> XLR 1 hot.
Ring -> XLR 2 hot.
What's feeding XLR colds? You might be able to ground them to the sleeve but whether it works or not is a crap shoot - depends on the gear design, IIRC.

[nerd]

I do this all the time at work. You can tie pins 1 and 3 together at the XLR end so the low isn't floating. As others have said an matching transformer is best but you can get by without one.

XLR Pinout:

1 Ground
2 High/Tip
3 Low/Ring

[RAILhead]

Sounds like I should just not worry about the XLRs, and just go 1/4"...

[nerd]

You'll run into the same problem if your 1/4" cables are tip, ring and sleeve. It could be possible that your cable was wired out of phase; tip to XLR pin 2 on one and ring to XLR pin 3 on the other. This all depends on the receiving circuit if you'd hear it or not.

XLRs are balanced audio so pins 2 and 3 are 180 degrees out of phase of each other (the transmitting equipment does this). On the receiving end they are put back into phase and mixed together. Any noise that got introduced on the wire goes through this process as well. The noise that was introduced into the line is in phase so now when the receiving end is putting the audio you want to hear back into phase the noise is now 180 degrees out of phase and is canceled out at the mixing stage.

Wire it this way:

1/8" Tip - #1 XLR Pin 2
1/8" Ring - #2 XLR Pin 2
1/8" Sleeve - #1 & #2 XLR Pin 1

Then jumper Pins 3 and 1 together on both XLRs so the unused pin 3 isn't floating.

[RAILhead]

I'm only needing to go from stereo 1/8" to left and right, not 1/4" trs.

[nerd]

What connection is on the other end of the 1/8"? XLR only?

[RAILhead]

Yes, it's a splitter. 1/8" stereo going to a left XLR and a right XLR, males.

[nerd]

You'll be fine wiring it the way I outlined above. You mentioned your current cable metered out with tip and ring going to both XLRs so it was wired wrong.

[Doofy]

Originally Posted by RAILhead 

Sounds like I should just not worry about the XLRs, and just go 1/4"...

Yep. Much easier.