Odd XLR Wiring........

  • Thread starter Thread starter blazingstrings
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blazingstrings

dgatwood can **** himself
Hey all,
I was looking through the manual for my Fostex model 812 mixer and noticed a weird part about the XLR connections on it.

It says:

"35. XLR input jack
This is an XLR Type Jack. It is intended for a balanced in-
put signal(3rd pin is HOT)."

Now from everything I have learned and read online and from people, I thought that Pin 2 was hot, Pin 3 was Cold and pin 1 was ground.......... :confused:

So why would this mixer say that? Or am I looking at a foren manual?
I hope that I have been wiring things the right way or I'm gonna geta few calls from folks...... :o

I also have plugged a few condensor mics into that mixer with a store bought XLR cable and used the internal Phantom power of the 812 and had no issues.

So is the manual wrong or am I wrong?

Thanks for any help.

-Blaze
 
A LOT of manufacturers had their own ideas on pin out. You have to be aware of that. Pin 2 is normally hot but sometimes not.
 
Hey track thanks for the input.

So heres a question if I have plugged in mics and they worked does that mean that everything is fine or does it mean I can still damage something?

-Blaze
 
Ok so what I read is that I would need to switch the wiring just for the Fostex.

Meaning Wire Pin 3 as hot and Pin 2 as cold and then wire the patch bay the right way with pin 3 going to the tip on a TRS and pin two as cold on the ring.

Does that sound correct or am I doing that wrong.

The manual shows pin 3 as hot in a diagram.

I also read that the issue was with phasing, that if wired backwords I would have phase reversal. Does that sound right?

Just wanna get this right on that mixer.
I doing this tonight, so any answers that can be provided in a timely manner ofcourse gain rep points HAHA! :D

Thanks as always

-Blaze
 
It won't hurt anything, it just inverts the signal but that has potential of being a big problem (polarity wise). I ran into the same thing when I got my Tascam console. Pin 3 is hot on it but everything else in the studio is pin 2 hot.
 
Cool thanks for the help man! This place never leaves me high and dry.

I guess I'll wire it the way the manual says and hope that avoids and headaches.

Thanks again.

-Blaze
 
blazingstrings said:
I also have plugged a few condensor mics into that mixer with a store bought XLR cable and used the internal Phantom power of the 812 and had no issues.
Click to expand...

Not familiar with that mixer, but does the manual say the mic in's are pin-3 hot? Or are you talking about XLR line in's being pin-3 hot? Just curious.
 
Confused......

Ok so I called a friend who has built more than a couple of studios......
He said "Plug in a regular(pin-2 hot) xlr cable into the mic in and a condensor, turn on the phantom" So I did that and the mic worked fine.
He said if the mic doesnt work then flip the wires.
I fliped the wires anyway to see if it worked that way and it did.

So to clarify, a XLR cable with pin-2 hot and pin-3 cold worked
and a XLR with pin-3 hot and pin-2 cold worked as well..... :confused:
So! Am I ok doing it any which way?

Raw-Tracks, Its the XLR Mic input that can be phantom powered.......

Theres a XLR in and a TRS line in as well, I'm using the XLR mic in.

And the manual says what I posted above.

Thanks for any help.

-Blaze
 
One more odd question.

I want to wire a TS plug to a TRS plug for the unbalanced direct outs on my 812 to connect them to a sound card with balanced ins.

According to the links I have read I need to:
Conect both the hots to each other and the sleave of the TS to the Ring of the TRS and then the sheild to the sleave of the TRS.

Is that info correct?

Thanks again.

-Blaze
 
I find that very strange that the XLR mic in's are wired pin-3 hot, but it doesn't surprise me. Almost all, if not all, mics are wired as pin-2 hot. Now, this may be something that doesn't really matter at all to you. A pin-2 hot mic pluggeg into this mixer will have it's polarity invertered. However, if all of you mics are plugged into this mixer, then all of their polarities will be inverted. Therefore, relative to each other, their polarity will be the same.

For clarity's sake, you mention that your friend told you to plug "a pin-2 cable" into a mic to test it. There is no such thing as a "pin-2 hot cable". A cable is generally wired pin to pin and only carries signal. The same cable will carry a pin-2 hot signal just as easily as a pin-3 hot signal. It's the gear at either end of the cable that determines which pin is hot.

My guess is that your friend was talking about using a cable where pins 2 and 3 are crossed, a polarity inverting cable.
 
Raw-Tracks, you and my friend are right.
You mirrored what he said.

When He said a "Pin-2" hot cable he ment a cable that was wired pin to pin, meaning pin-2 was wired to pin-2 at both ends.

But what I did was wire the cable so pin-3 was the hot at the mixer end and pin-2 was hot at the other.

I am still lost on wiring the un-balanced 1/4" direct outs of my mixer to a balanced patch bay and then conect that to the balanced 1/4" ins of my M-Audio delta 44............. :confused:

Thanks again!

-Blaze(up to my ears in wiring crap)
 
In the early days, there was no standard on XLR pin assignments.

You'd be surprised at the number of pieces out there that require pin 3 to be hot.

In the case of the phantom power, alot of condensor mic will work that way since they're transformers (essentially) and the juice will pass either way.

I have an old stereo 31 band EQ where pin 3 is hot. I just made a couple of conversion cables. Red wire to pin 2 on the conventional piece to pin 3 for the EQ.

FOR TRS connectors, do the same. Pin 3 will go the tip instead of pin 2. Pin2 will go to the sleeve, and 1 to the shield.

BE SURE TO LABEL THOSE CABLES AS PIN 3 HOT!!!

God knows, I was troubleshooting like hell one day when I grabbed a converted cable by mistake only to have almost no audio coming outta that channe!
 
alien said:
In the early days, there was no standard on XLR pin assignments.

You'd be surprised at the number of pieces out there that require pin 3 to be hot.
Click to expand...

That is true for line level devices. However, in my experience, it is extremely rare to see mic's and/or preamps that are wired pin-3 hot.
 
I no for sure that many consoles and amplifiers were wired for pin 3 hot back in the day. I have some old Crest and QSC amps kicking around that are pin 3 hot, and my old Allen Heath system 8 was pin 3 hot. Making the adaptor cables is the best way I can think of to fix the problem. Please make sure that you do clearly label them like mentioned above though:) Also, if all of your tracks are phase reversed, there would not be any major issue. However, if you lay a track or two through an outboard preamp, then some problems may start to creep in. This is why it is a good idea to correct the prblem once and correct it right away. Then it will never be an issue for you:)
 
blazingstrings said:
Raw-Tracks, you and my friend are right.
You mirrored what he said.

When He said a "Pin-2" hot cable he ment a cable that was wired pin to pin, meaning pin-2 was wired to pin-2 at both ends.

But what I did was wire the cable so pin-3 was the hot at the mixer end and pin-2 was hot at the other.

I am still lost on wiring the un-balanced 1/4" direct outs of my mixer to a balanced patch bay and then conect that to the balanced 1/4" ins of my M-Audio delta 44............. :confused:

Thanks again!

-Blaze(up to my ears in wiring crap)
Click to expand...

If the Direct outs are unbalanced. Then just use a TS cable to the patchbay. Then use a ts cable to the ins on the soundcard. The patchbay will automaticaly recieve the signal from T and will sum The R+S due to the fact it makes contact with both already. As long as the soundcard can take an unbalanced signal it will work fine. Just avoid long cable runs. Like I said before A DI inbetween would work to impedence match for use with balanced devices hooked up to the patch bay. To do it with only unbalanced cables would render the entire patchbay unbalanced so to speak. Because you would not be able to use a balanced cable for any other pieces that are going to be put in the path of either of these devices. Furthermore it also depends on Normal/half normal or denormaled use
 
petermiller said:
If the Direct outs are unbalanced. Then just use a TS cable to the patchbay. Then use a ts cable to the ins on the soundcard. The patchbay will automaticaly recieve the signal from T and will sum The R+S due to the fact it makes contact with both already. As long as the soundcard can take an unbalanced signal it will work fine. Just avoid long cable runs. Like I said before A DI inbetween would work to impedence match for use with balanced devices hooked up to the patch bay. To do it with only unbalanced cables would render the entire patchbay unbalanced so to speak. Because you would not be able to use a balanced cable for any other pieces that are going to be put in the path of either of these devices. Furthermore it also depends on Normal/half normal or denormaled use
Click to expand...

Thanks again Peter. the patch bay is sort of a weird one, Its actualy just a ton of stereo neutrik jacks mounted in an old gutted patch bay(what was in it was horible).
Nice thing is I can decide how I want to wire each point.
I guess I'm not to versed on normal/half normal or denormaled........ :o

Hah! My buddy just left me an e-mail to say pretty much the samething you said! Wait......... Is that you Anthony? :D


xstatic said:
I no for sure that many consoles and amplifiers were wired for pin 3 hot back in the day. I have some old Crest and QSC amps kicking around that are pin 3 hot, and my old Allen Heath system 8 was pin 3 hot. Making the adaptor cables is the best way I can think of to fix the problem. Please make sure that you do clearly label them like mentioned above though Also, if all of your tracks are phase reversed, there would not be any major issue. However, if you lay a track or two through an outboard preamp, then some problems may start to creep in. This is why it is a good idea to correct the prblem once and correct it right away. Then it will never be an issue for you
Click to expand...

I did just as you said there xstatic, I wired all pin-3's as hot and then back to normal(pin-2) after that.
My friend also mention that in his e-mail to me(dang, all the info at once) that the pre amp would be pahse reversed if wired wrong. I have a tube mp for ocational use and wouldnt like problems.... HAHA!

Thanks to all who have helped.

-Blaze
 
Track Rat said:
It won't hurt anything, it just inverts the signal but that has potential of being a big problem (polarity wise). I ran into the same thing when I got my Tascam console. Pin 3 is hot on it but everything else in the studio is pin 2 hot.
Click to expand...

Shouldn't matter as long as you consistently use the balanced inputs and outputs, since it would be inverted on both ends. Of course, if you're mixing unbalanced gear, those lines will be phase inverted from what you would expect.
 
Above at some point it was mentioned that if a connection is unbalanced, to just use a TS cable. Most of the time this is OK, but it is not correct. Unbalanced and TS and balanced and TRS are not inherently tied together. Unbalanced is not ALWAYS -10, and you cna have +4 unbalanced. I had a console that sent a -10 signal once off the ring of the jacks. In this case a TS cable would not have been what you want to use. Once again, in general this works, but try and not take it for law just because most manufacturers happen to do it.
 
In days gone by, most American stuff was pin 3 hot; most European stuff was pin 2 hot. Europe won, so now virtually all XLR stuff is pin 2 hot. The least fun, but most sensible, way to handle this with older gear is to take it apart and CHANGE all XLR's to pin 2 hot; then you can stop thinking about it til another piece of vintage gear shows up.

The reason phantom worked either way, is that both low and high (pins 2 and 3) get the SAME phantom voltage, and pin 1 gets the ground - this lets the twisted pair that's connected to 2 and 3 also cancel any noise that may ride on the phantom supply, so the mic doesn't get noisy power. Switching 2-3 won't change the power, but it WILL change the polarity of the mic.

Ideally, each mic in a studio should be wired so that a positive pressure at the diaphragm results in a positive voltage (first half-cycle) at the output of the mic, and this polarity should be maintained throughout the signal chain. Every once in a while you'll find a mic that's wired backwards, and if you end up using it with another for stereo, you'll lose bass and get some comb filtering artifacts in the stereo pair.

HTH... Steve
 
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