Phantom power for pedalboards? Would it work?

[Morocotopo]

Hi. I just finished my new plywood pedalboard, and I realized that I will have three cables going to it: audio in, audio out, and power. The power can be a problem, stepping on it could unplug it, dangerous, etc.
So I thought, if microphones work on phantom power, could stompboxes do the same?
Could be something like this:



I don´t know if phantom powering is possible only with balanced lines, in that case the "adapter" boxes should also convert unbal to bal and bal to unbal. This idea, I assume, implies a buffer for the audio at the pedalboard box, so you would lose the "guitar direct to amp" connection, available if you use all true bypass pedals.
Of course the boxes circuits have to be designed... (regulated) power supply, phantom feed, buffer(s)... I never investigated much phantom power circuits, but from the little that I read/saw, they don´t seem to be THAT difficult to do. Maybe I´m wrong.
Advantage: the power supply doesn´t have to be AT the pedalboard anymore, can be near the amp. Room for one more pedal (maybe).
What do you think? Dumb idea? Not possible? Too much effort to eliminate a cable? Doable? Too much red wine? 

Morocotopo

[petemoore]

  If it works for Mics why not?
  As long as the PS can supply the current...
  And it's the right DC voltage for what you want.
  Phantom is generally 48VDC ?, I don't know if there's a regulator which can convert 48vdc to 9vdc..perhaps more than one with heat sinks ?
  I can see where this would be handy if you were running the signal into a mixing board, but then you'd probably want to match impedance...and to run an amp you'd need the mixer or alternate power supply to run the pedals.
  Beside whether or not to, I'd look into the current rating of the phantom power, then what chips could be used to drop the voltage to what you want, matching impedance of pedal output to a mic channel input, actual wiring and stuff like that.

[Morocotopo]

 OK, I just thought of a disadvantage: the "adapter" box 2 would have a power transformer AND audio circuits inside, possible hum pickup situation.
Possible solution: put the transformer inside a box, and that box inside ANOTHER box with the audio circuits, with the 1st box grounded. What do you think? (Toroidals unavailable here)

Morocotopo

[petemoore]

  Transformers don't work with DC.
  See GEO, 'power supply for effects'

[sfr]

If you're worried about losing the power connection (I've had this happen - overzealous singer steps on the cable and unplugs your pedal power supply and you've got no signal!)  A quick protection against no signal is the setup EH uses in some of the Memory Men - (I believe that's who does it?)  a bypass setup with a relay; if you lose power, the relay closes, and you still get (unaffected) signal through. 

Should be easy to implement, surrounding your entire pedal chain, plus you could rig up a footswitch to drive the relay, and have a panic button to bypass all your pedals. (Which turns out to be useful at times - trust me)

[Morocotopo]

Thanks for the answers. Of course, the idea is NOT to use 48V as in mics phantom, but whatever voltage and current pedals require (eg, 9V 500-1000 mA), so the power supply/phantom circuits have to be designed for those values.
Pete, I don´t quite get your answer about transformers... will read GEO.
Sfr, my main concern/idea is to do away with the need for a power cable going to the pedalboard and the need of a power transformer at the board, the "drunken singer unplugging power" scenario is not the main problem to solve to me (of course there´s always the "dumb guitarist kicking the wrong thing and unplugging power" scenario to take care of  ), that was just an example, but thanks for the suggestions.

Morocotopo

[jakenold]

I am using such a thing myself for my board. As I am changing my gear pretty often, I wanted to be safe on the power side, so I have a big transformer in my rack, able to supply 20V AC / 10A.

I have a cable with 20V AC going to the board (not with the signal, that would be a bad idea) and into every of my effects (except the wah and octaver) which has built in 1:1 transformers and regulators. It works very well I must say!

[ADR]

Why not just get some of that plastic coil stuff to make a cablesnake?
http://cableorganizer.com/spiral-wrap/

That's what I do and have never had the cables kicked out cuz I velcro the snake to the board, kinda like an overall strain relief, so if it does get tugged, the whole board gets tugged with it. But that almost never happens. I was originally thinking of a custom multicore cable to do all this, but this was a lot simpler solution.

The power brick is by the amp and feeds a DC extension cable that is in the snake. The DC extension cable was $3, and a 15 ft/1/2" diameter snake coil was $7 at the local electronic supply store.  (I also have other footswitch cables inside the snake to toggle my tape echo unit by the amp and the amp's trem and reverb).

A tenner was all that was needed to wrap it all up cleanly.

[grapefruit]

That should work ok with either XLR or TRS jack sockets. Pin3 or Ring could be for +9V, Pin2 or Tip for signal, and pin3 or Sleeve for ground. If you use decent mic cable with hefty shield wiring sharing the power and signal ground shouldn't be an issue if you have a regulated supply.

If I was doing it I'd probably use a switchmode 110-240Vac to 12V plugpack or module, and then use a linear 9V regulator.

This is not phantom power. It's simply using another wire in the audio cable to supply power. Mic phantom power circuits rely on having a balanced input, and can't provide very much current. To be able to provide more current the input impedance would be reduced.

Stew.

[Morocotopo]

Thanks again all for the answers. Grapefruit, so it could be as simple as using a 3 conductor cable and sending power (DC) through one, with a shared ground /shield) (0V)?
What do you think about hum/noise pickup from having power and audio sharing the same cable? Would that work reasonably?
I don´t know what a switchmode plugpack/module is...  i guess it´s NOT a regular transformer. It wouldn´t work with a regular one?
If it did, I could have a regulated power supply (LM317) at the box near the amp, supplying 12V DC through the cable, right?

Morocotopo