Balanced output from your guitar...

[earthtonesaudio]

Seems so simple to do, and easily un-done, that I am suspicious I'm missing some important detail...

The output of a typical magnetic/passive guitar pickup is two out-of-phase AC signals plus a shield.  In most guitars one side of the pickup is grounded and the other side goes through the volume/tone/switches and on to the output jack.

What if you used a stereo output jack, and instead of grounding one side of the pickup, attach it to the ring connection of the TRS jack?  Your volume/tone controls would now be common-mode instead of ground referenced, and the output would be balanced with a shield, just like a typical dynamic microphone. 

The first pedal could have differential inputs and thus eliminate common mode noise between the guitar and the pedal.  This seems like a good thing.   

Of course, if you plugged in a standard mono cable, the ring would short to the sleeve and it'd be electrically identical to the "normal" setup.

Crazy or no?

[Ripthorn]

Been a long time since I poked around in my guitars, but seems to make sense to me.  I just may have to give it a go.  You could even have a standalone box at the front of your pedalboard or something to invert one signal and sum together, should take just an opamp really.

[R.G.]

It is indeed simple and easy in theory. There's a slight issue of what "ground" is.

If you did this right, you'd wind a center tapped pickup, ideally bifilar wound,  and use the CT for signal ground. That gets you the interference cancellation you're looking for. If you only use a single coil, you're going to have to somehow reference the signal to the nominal zero volts of the remote signal ground and the shield. Without some kind of centertapping and ground reference, you don't get all the advantages of cancellation you're looking for. It's worth dinking with, but I think the single coil used as a floating differential source may give you some problems.

The other way to do this is with an onboard single-to-double ended converter. This takes the single ended signal and converts it to a low(er) impedance signal which does satisfy the needs of a shielded twisted pair connector and input.

I've often speculated that the guitar world would have been much more hum-free  if early tube designers had used one more half of a duotriode to make the front end a diffamp instead of a single ended gain stage. Of course, we're completely straitjacketed by history. With all the single ended guitars and amps in the world, and the degree of guitar ancestor worship that exists, there's slim to none chance to go make guitars balanced output now.

[edvard]

Interesting idea.
R.G. is right though. Take a lesson from the early days of residential AC electricity. They "floated" the output and it picked up DC offsets sometimes in the thousands of volts range. That's why two-wire AC today ALWAYS has one end earthed and people write in BIG RED LETTERS on bipolar hot/cold/ground equipment to never plug in if the ground lug is damaged or missing.

With the single-ended guitar systems we have now, there's no drift because one end is always grounded.
Without a dedicated ground reference, the differential signal will drift and you'll be quite prone to picking up enough DC to do anything from giving you a mild shock to becoming your own personal light show depending on the gear you're playing through and atmospheric conditions where you're gigging.

That said, how about doing it with humbuckers? One end to ground and the other ends feeding the equipment?
How would you hook up the tone controls, etc? Dual pots on everything?
Sum the output with an opamp just like Ripthorn suggested and you should be good to go with any single-ended gear.

[Minion]

You could use a opamp buffer then go into a DRV134 Ballanced line driver , could make it small enough to fit in yer guitar and run off of a 9v battery or even Phantom power .....


Cheers

[jimbeaux]

Gibson produced a Les Paul "Recording" Model - that featured Lo-Z pickups back in the 60's - 70's?

I did a quick search & found these links that might help.

http://www.guitar-parts.com/images/lespaul.jpg

http://music-electronics-forum.com/t3737/

http://www.ntw.net/~w0ui/family_webpage/linkpages/music/music_lespaulrecording.htm

- Jimbeaux

[wavley]

I know that this is a dead thread.

I'm not sure of the details but I remember seeing the bass player of the Violent Femmes using a balanced bass rig for his electric, XLR on the bass and XLR on the amp, as to how this was wired and if it was truly balanced, I don't know, I never asked and I was just a dumb drunk kid back then so I'm not sure I would have understood anyway

[edvard]

Didn't he play an acoustic?
If so, there might've been an actual mic in there, so an XLR would make sense.

[earthtonesaudio]

Cool stuff.  I got distracted by low impedance pickups.     I think the "center tapped" humbucker would be cool to try.

[wavley]

Didn't he play an acoustic?
If so, there might've been an actual mic in there, so an XLR would make sense.

He plays an electric too, I always wondered if he just had an xlr on the electric just to match the output configuration of his acoustic or it was actually a balanced output.