[avahifi]

XLR Jacks come either with the three pins exposed, or with them in three holes.

It would seem rational to use the unexposed jacks for outputs, to protect against shorting the output of the equipment powering the jacks.  However I have seen production equipment with this reversed; the exposed pins on the outputs, the protected pins for inputs.  This seems kinda backwards.

Is there a normal convention for which should be used for outputs and which for inputs.  Also what is the convention for the + signal and the - signal and the ground connection?

Thanks,

Frank Van Alstine

[mgalusha]

Frank,

The standard pin out is pin 1 ground, pin 2 +, pin 3 -. All the pro gear I've used has the males (pins exposed) as the output and the female as input.

mike

[Speedskater]

Think of the one with pins (the male) as the signal source. With the female connector as the receiver (input) of that signal.

[macrojack]

Yeah, the male is the injector, just like in reproduction. Some companies, for some reason, wire their stuff with pin 3 as positive. This does no harm but does reverse phase.
XLR (balanced) connections offer 3 benefits over RCA (single) according to what I've been told.
1.- Connectors lock very securely.
2.- Less signal loss over long distances.
3.- Better noise cancellation due to presence of both polarities.

None of those 3 advantages would seem very meaningful in the typical home stereo model except possibly number 3.

[Wayner]

If we are to go by industrial standards, such as suggested by NFPA79e, the use of the pin XLR as an output is a violation of code. The pins carry signal (voltage) and are susceptible to shorts.

However, the industry has gone the other way, with pins being the output, receptacles being the input. I think what Frank is really trying to ask is should we continue to abide by what the industry is doing, or do it the right way with the pins as the input, receptacles as the output.

Personally, I think mic manufacturers started the problem putting pin-outs on the mics and the chain just kept going that way, even if it was wrong.

Wayner 

[macrojack]

That seems to make sense. My wall outlets are female.
But there sure is a hell of a lot of stuff out there that would need to be retrofitted for a change to succeed. We're talking about revolution, range war, blood in the streets. Could be that this is one of those situations where the cure would be more disruptive than the disease. The 2 or 3 pin positive is pain enough. Having to change one end of every cable and all inputs just isn't likely to be accepted out there in pro world. The question reflects intelligent thought, though. Maybe that's what's wrong with it.

[Davey]

For signal purposes, using male pins as outputs is not an issue (with regards to shorting) because inside all equipment will be a built-out resistor in series to decouple capacitive loads.  You could short the output pins to ground and no damage will occur.

For AC wall power, and other forms of power connections, yes, it is a normal practice to use female connections for voltage sources.

Cheers,

Dave.