FOTM: 5-pin Headphone Jack

[luvdunhill]

heh, but seriously.

If you only have room for a single jack, and want to support balanced (4-channel bridged) and single ended cans, what do you do?

Two options as I see it.

Use 4-pin jack and tie ground to the shell and/or case or use a 5-pin jack and have a dedicated pin for ground. If the first case, I'm not sure if there are 4-pin female jacks where the where the "shell connection" can be isolated from the case. If this isn't possible, then is 5-pin the only real option?

I cannot believe this hasn't come up before. Thoughts?

[cetoole]

I think there is some standard, IEC or something, which specifies a 5 pin xlr for balanced headphones. It does make a good deal of sense.

[grawk]

It would make sense if anyone else did it. Go 4 pin or go home

[luvdunhill]

It would make sense if anyone else did it. Go 4 pin or go home

meh. I'd like a way to convert to single ended and only have a single jack...

[justin]

sorry, no way no how can you convert 4-pin to single ended.

what if your amp design allowed the 2 minus outputs to be shorted

[luvdunhill]

heh, you're quick. I cannot see why that wouldn't work, but then again, I could imagine designing for that condition..

Edited February 1, 2010 by luvdunhill

[Dusty Chalk]

I cannot believe this hasn't come up before. Thoughts?

Yeah, what are you doing with the 5 connections? I understand 4 of them: +/- L/R, but the 5th one eludes me. I'm with grawk -- 4-pin, a la AKG K1000.

[grawk]

Oh, it's L+/L-/R+/R-/GND so that you can tie in just L+/R+/GND for single ended and not cross grounds.

[luvdunhill]

right. otherwise, there isn't a way to connect a single ended headphone to a 4-pin jack.

[grawk]

You said the method at the top. Tie the shell to ground. But I don't think I'd go out of my way to provide that option anyway.

[luvdunhill]

I'd be worried about noise in that case. If the shell cannot be isolated from the outer connector, it could be a source of ground loops and other nasties. Why not go through the trouble of supporting single ended headphones?

[grawk]

So make room in the case for a single ended jack?

[luvdunhill]

So make room in the case for a single ended jack?

I only have room for one jack

[grawk]

back panel

[luvdunhill]

back panel

no room. Top is completely covered too

[grawk]

I see room on the sides

[Dusty Chalk]

Oh, it's L+/L-/R+/R-/GND so that you can tie in just L+/R+/GND for single ended and not cross grounds.

right. otherwise, there isn't a way to connect a single ended headphone to a 4-pin jack.

You mean, three-connector, right? Because all dynamic headphones are two single-ended drivers. It's just a matter of how easy it is to access that point where the 3 wires become 4, right?

I agree with "provide a separate jack" for those.

[grawk]

I think he means without rewiring the headphones, or reterminating, etc.

[Dusty Chalk]

No, I don't think he means that, since he's talking about a 5-pin jack -- he'd have to do that anyway.

[grawk]

adapter cables

[luvdunhill]

wait, I thought about this... even if you can do this (which by the way, I thought of a case where you could do this, a concertina output 'cause I did this in my preamp, but not much good at driving much of anything), how would this work with a single 4-pin jack? just because you can short the minus to ground, doesn't mean you can short them to each other and get a usable reference

and, Dusty I just mean use a single jack. You need a ground reference for the single ended headphone option. Adapters are fair game.

All this to say, I think finding an isolated four pin jack with a separate shell connection is the way to go...

[Dusty Chalk]

Alright, so the two hots go to L/R +; ground gets split and sent to L/R - of the drivers. Right so far?

On the amp side of the same sitch, where does L/R - go? Unterminated? Loaded? Switched-in-loads? Switch out those half of the amps (so that they don't present some weird load, and yet are green and don't consume power at the same time)?

The case I am discussing is the unreterminated single-ended headphones discussed earlier.

[swt61]

Not sure about that shell connection.

[mypasswordis]

Acoustic Revive RGC-24 Ground Conditioner

A blend of special ores is clearly the solution

[luvdunhill]

Dusty:

Yeah, that's right. So far. So, you're asking the same question on the amp side. The L/R- is unterminated. I definitely don't want a switch there.

So, in summary the problem is with a 4-pin jack, or even two 3-pin jacks, that are used on the output of a four channel design, you cannot "convert" this using any combination of adapters, custom or otherwise, for use by a single ended terminated headphone. You need a ground reference.