Supply power to guitar through cord?

[taang]

Hey all,
I'm fairly new to pedal wiring/electronics, etc. and I have a fairly crazy idea. Here it goes: is it possible to run a power supply through a stereo guitar cable to power on-board effects on the guitar? I'd like to do this because there's no room in my guitar for batteries AND effects, and routers are scary.

The thing stopping me from just trying it is that I'm not sure which type of cable to use, or whether or not it's okay to shield a DC current (if I use a mic cable or something).

My idea is to have a box on the floor that would add the power to the cords. Here's a diagram:

EDIT: whoops, I realize that the LED is wired completely wrong. Just pretend it's a fancy jumper or something.

Any thoughts?

[G. Hoffman]

I'm pretty sure I wouldn't want to put power through your pickups.  I've got a feeling it wouldn't be very good for them (42 gauge wire is pretty damn small, and can't handle much current!).  You could, I suppose, block the DC with a cap, but you are still going to have problems with the guitar signal modulating the power to your effects. 

If you are thinking this is something like phantom power for mics, it's not.  Phantom power runs +24 volts on both sides of the balanced line.  Because one of those lines gets inverted prior to any of the electronics, it gets canceled out.  I have to admit, I'm not entirely sure how they keep the audio from messing with the DC, but at a guess it has a lot to do with the much higher voltage, and the much lower voltage and impedance of mic signals.


Gabriel

[GibsonGM]

The only real issue I see with providing 9V to the on-board stuff is possibly coupling noise into your signal path. But, it can be done w/a stereo cable as long as signal and power are kept separate, sure.
 
However, the basis of stability, IMHO, is simplicity!  It's easier to throw a malfunctioning pedal off your pedal board rather than have it hard-wired into the axe.  Jerry Garcia used to run a stereo cable that sent his signal out to the effects, then back to the guitar before his volume pot - so the level would be the same regardless of vol. pot setting.  That is more 'logical' in terms of 'what if something goes wrong?' than having your guitar dedicated to the effects.  If you have to have stuff on board, good batteries might be more 'forgiving' than being tied to a wall wart.

Just my 2 cents!   

[Mark Hammer]

If you want super long-lasting power, get yourself a plastic box of suitable size, and stick a half-dozen C-cells in a suitable battery clip, and run the "phantom power" up to the guitar via a stereo cable.  While you're at it, you can feed that same 9vdc to your pedals too.

[Processaurus]

What is the DPDT switch in the guitar supposed to do?  It looks pretty wrong, whatever it is, ha ha.  Power's getting hooked up to either the guitar pickups or the output of the effects...  Also you don't put an LED in series with the power (+) to show it's on, you put it in parallel (between the + and - from the wall wart).

What you're trying to do is super simple, I think you have it, you just run +9v up the ring on a TRS cord to the guitar's effect's power input.  You run the effects out down the tip.  Grounds are all connected on the guitar and go to the sleeve.  Power supply (-) is connected to the sleeve in the box on the floor.  Ba da bing.

Only hitch is that if a mono plug ever gets plugged into the box it will short out the power supply.  There should be a tiny value fuse or circuit breaker or something, or use a power supply that has built in short circuit protection.  Or use an XLR cable instead of TRS.  You could even put one of those fancy 1/4"/XLR jacks on the guitar so you can play it with a regular TS cord as a regular effectless guitar.

[terminalgs]

I suggest a ghostbuster style back pack with a large power supply.

you could do it with a single conductor regular guitar cable:

guitar pickup --> audio AC signal (0vdc) -->  coupling capacitor  --> AC signal + 9vdc --> guitar cable -->  pedal -->  AC signal + 9vdc  -->  coupling capacitor  --> AC signal  (0vdc).

inject the the 9vdc at the pedal  on the cable side of the coupling cap,  pickup the 9vdc on the guitar on the cable side of the coupling cap.  DC can't go through a cap, AC can.

AC signal will ride on top of the DC.   off hand I don't think you'll have a problem.  condenser mics let their AC signals ride on top of 48vdc phantom power in some cases from the preamp to the mic.   

you'll have to use fairly large coupling caps as to not discriminate against the full spectrum of frequencies your pickups will produce.   you could try a .01uf or even a .1uf if you have space.   use quality caps too.

I don't think it'll effect the sound,  but it might.  try it.  with coupling caps, your pickups will be safe.

depending on the length of the cable, you  might have a low current 9vdc at the other end  if your supply is a 9vdc battery,  i dunno,  but you'll have that with any  of the idea that you devise.  (except the ghostbuster backpack).

[taang]

Thanks guys. So the DPDT is for in the case that if I wanted to use it as a regular guitar. I'm considering the backpack idea, or the 1/4" TRS/XLR jack idea.

I'm thinking about putting some sort of EQ booster (i.e. red ranger) and some custom fuzz box in it... I guess if the pedals have a super low current draw, then batteries seem the best way to go. Does anybody know how to measure power (current? amps?) draw?

(and don't worry about my pickups... they're cheapo ceramics. I need new ones...)

[Gus]

http://www.aronnelson.com/gallery/main.php/v/gus/9pp.GIF.html?g2_imageViewsIndex=1

In the gallery for some time

[chi_boy]

There's a commercial solution too:

http://www.guitarelectronics.com/product/PMTXBAT9/9_Volt_External_Battery_System_for_Active_Electronics.html

[grapefruit]

you could do it with a single conductor regular guitar cable:

guitar pickup --> audio AC signal (0vdc) -->  coupling capacitor  --> AC signal + 9vdc --> guitar cable -->  pedal -->  AC signal + 9vdc  -->  coupling capacitor  --> AC signal  (0vdc).

The problem with this is that any power supply noise will be added to the guitar signal. This is avoided in mic phantom power arrangements because they have quiet power supplies and the mic cabling is balanced, so any power supply noise is cancelled out when it gets to the mic preamp.

IMO the easiest/best way to do it would be with a 2 conductor shielded cable (mic cable) with a TRS socket on the guitar. I'd put an XLR on the power box but that's up to you. If you keep the signal on the tip then you won't have any problem plugging a regular guitar cable into the guitar and plugging it into an amp or whatever without using your on board effects (if you have a way of bypassing them).

Cheers,
Stew.

[FiveseveN]

"Phantom power" has come up around here before and I personally find it great, which is why I recently wrote a more detailed article about my take on it: http://xonedesign.ro/ip/2009/12/guitar-phantom-power/
Hope it's useful.

[Mick Bailey]

Have a look at this;

http://www.till.com/articles/PreampCable/index.html

Now consider the preamp circuit being built into your guitar and you have the basis for a design.