Phantom for pedals

[Doug Siddons]

I was discussing custom stage boxes etc on another forum and this idea came to me.

 

The scenario is a player at front of stage with his effects board at his feet requiring power. Now most of these pedal effects are 9-12v dc, would it be possible to run these with a custom plug and necessary resistors and filters in line etc from phantom power or would the current draw be too much?

 

It is just a theoretical exercise and I'm aware of the need for different polarities for different pieces of kit etc but the its just the basic idea

[nb705]

You'd have to check the current draw on the pedals, but there's a fairly good chance it'd be too high

[Richard P-W]

5 Pin XLR lead wired with starquad cable and then breakout leads each end from XLR to Jack and DC power connectors. No need to phantom anything...

[Shez]

You can only draw a few milliamps from phantom power - there's very little chance you could run pedals from it.

[MarkPAman]

There's about two thirds of a Watt available from phantom IIRC.

 

The smallest pedal PSU I can find in my box is 3 Watts.

 

So that's a no!

[Simon Lewis]

The PSU might be able to source that overall, but the maximum per channel is typically 14mA in a short circuit situation. The standard calls for 10mA max.

[Stuart91]

A church I know were very keen on a clean stage, so fed the power for pedals down XLR lines into floor pockets. It caused carnage. I didn't get to the bottom of the problem for them, but soon proved that the pedal setup was causing all kinds of noise.

 

The setup was that the guitarist had a radio pack. The receiver was sitting on top of his amp, behind him at the rear of the stage. The effects loop of his amp plugged into a pop-up floor box beneath it, with an unbalanced line running from there to a floor box at his feet. Short patch lead out of floor box, into pedal, then another one back into the other line on the floor box and back to the amp.

 

Meantime the power for the pedal is running down another line, with the wall-wart PSU wired into the stage box under the amp, and a skinny line running to the the floor box at his feet. The last remaining space in the box is used for an XLR line for his vocal mic.

 

It looked good, but sounded terrible. I had a hunch that the pedal was misbehaving due to voltage drop on the long supply line, and a long unbalanced run was inducing lots of noise. In the end we had to give up on the pedal entirely. They might have found some other way to implement it afterwards.

[dbuckley]

The answer, of course, is MIDI, which goes quite nicely down mic cables and multicores, and, as the receiver is opto-isolated, MIDI plays well with other earths in the system...

[Stuart91]

The answer, of course, is MIDI, which goes quite nicely down mic cables and multicores, and, as the receiver is opto-isolated, MIDI plays well with other earths in the system...

 

But wouldn't the device generating the MIDI signal need a power supply of some kind?

[dbuckley]

Yep, and "phantom" MIDI leads are available, albeit not 48v phantom. An XLR cable has three pins, which is enough for power and MIDI with a bit of careful (albeit standards-bending) arrangement. But its still a lot easier than trying to get guitar signals through fixed cabling.

[Mixermend]

The limitations of Phantom power have been correctly detailed above, but one of the constraints is surely that the pedal outputs won't be connected to microphone mixer inputs - from where the Phantom is available.

 

MIDI uses a 5 pin 180 degree DIN plug and socket system, with the 2 outer pins 1 and 3 being unused. There is a 'standard' which connects +9 to 12 volts on pin 3 and uses pin 1 to return.

 

Some commercial products, are wired ready to accept this (MIDI foot pedal controllers for example) - which enables connection to them simply with one MIDI cable. It is easy to make a 'break out' box to feed the power down the cable - voltage drop is not a factor, as there will be 5 volt regulation within the pedal. Important to ensure that the MIDI cables have all pins connected though!

 

Certainly I think that is is very desirable to keep mains away from the feet of the musicians, especially 'wall wart' type power supply units.

 

Guitarists pedal boards are a different matter - but neat and safe powering schemes can be provided easily.