Adding Phantom Power to MIDI cable from Lexicon MX200 to remote footswitch for program change?

[DC-Choppah]

I need to be able to switch the programs on the Lexicon MX200 from a remote switch at the pedal board.

To do that, I need to add phantom power on the MIDI cable to power the foot switch.

I have this foot switch: http://www.tech21nyc.com/products/effects/midi-mouse/
which connects to the MIDI In of the MX200.

And the Lexicon MX200 is this: https://www.telonics.com/products/proau ... nual_B.pdf

So I want to put DC power on pins 1 and 3 of the 5-pin MIDI connector that goes to the switch.

The goal is to have the footswitch powered by the MIDI cable, so I can do remote program changes. This all works great if I power the switch from 9v. But DC power is limited at the board so I would like to use the MIDI cable for power too.

Any advice is appreciated.

[Sam Spoons]

I did this with a home built combo which had a 2U rack guitar rig built in (Boss GX700 and Marshall Mosfet power amp) with a breakout cable from the midi plug at the combo end to the midi pedal's PSU, it was a simple job to modify the Boss FC200 internally to connect pins 1 and 3 to the back of the power connector. You could make a midi cable with breakout connectors from both ends if you didn't want to go inside either unit. If you want the Lexicon to power the midi pedal that's a fair bit more complex and probably not something I would want to attempt.

[DC-Choppah]

I did this with a home built combo which had a 2U rack guitar rig built in (Boss GX700 and Marshall Mosfet power amp) with a breakout cable from the midi plug at the combo end to the midi pedal's PSU, it was a simple job to modify the Boss FC200 internally to connect pins 1 and 3 to the back of the power connector. You could make a midi cable with breakout connectors from both ends if you didn't want to go inside either unit. If you want the Lexicon to power the midi pedal that's a fair bit more complex and probably not something I would want to attempt.

Right. That was exactly what I was trying to decide. Do you modify the Lexicon to put 9v power onto pins 1 an 3? Or do you use a breakout cable and a 9v adapter cut into the MIDI cable?

When I searched for this on the SoS forums, I did find that some folks were recommending to modify the sending box to put 9V power onto the MIDI cable. This would end up nice and clean too. No need for another power adapter.

There is no need for a breakout cable at the footswitch. Just have to add 9V power to pins 1 and 3 back where it plugs into the Lexicon.

But I guess I should make sure that pins 1 and 3 are not connected inside the Lexicon since it may not be happy with 9V on those pins?

[N i g e l]

The only thing Ive seen phantom MIDI on was the Rocktron Replitone preamp.

The MIDI in was 7 pin [ is that some kind of standard ?] and was designed to power the Rocktron MIDI floor switch box.

The preamp only took ~1A but the PSU was ~3A a.c.

My main worry about powering a unit from the Lexicon would be putting a strain on the PSU/regulators or introducing noise into the audio.



[edit] better photo..

[Sam Spoons]

I did this with a home built combo which had a 2U rack guitar rig built in (Boss GX700 and Marshall Mosfet power amp) with a breakout cable from the midi plug at the combo end to the midi pedal's PSU, it was a simple job to modify the Boss FC200 internally to connect pins 1 and 3 to the back of the power connector. You could make a midi cable with breakout connectors from both ends if you didn't want to go inside either unit. If you want the Lexicon to power the midi pedal that's a fair bit more complex and probably not something I would want to attempt.

Right. That was exactly what I was trying to decide. Do you modify the Lexicon to put 9v power onto pins 1 an 3? Or do you use a breakout cable and a 9v adapter cut into the MIDI cable?

When I searched for this on the SOS forums, I did find that some folks were recommending to modify the sending box to put 9V power onto the MIDI cable. This would end up nice and clean too. No need for another power adapter.

There is no need for a breakout cable at the footswitch. Just have to add 9V power to pins 1 and 3 back where it plugs into the Lexicon.

But I guess I should make sure that pins 1 and 3 are not connected inside the Lexicon since it may not be happy with 9V on those pins?

Yes, if the connections are external I'd avoid the power getting onto the Lexicon. IME pins 1 and 3 are not routinely connected in midi devices (don't take that to be a universal truth), but they are usually connected in the midi cable. I actually made a breakout lead with a male to female 5 pin DIN with only pins 2 & 4 connected to the male which connected to the GX700 preamp/fx unit, the female also had 1 & 3 connected to a coax power connector for the FC-200's PSU. All I needed then was a 'midi' cable with all 5 conductors and the 'spare' pins 1 & 3 supplied DC power.

FWIW I would do the same again if I ever used a similar system (and I do have a couple of Boss VF-1 ½ rack guitar processors and the old FC-200) rather than risk messing with the internals of the processor, the control pedal was pretty simple to modify.

[N i g e l]

pins 1 and 3 are not routinely connected in midi devices (don't take that to be a universal truth),.

Ive just buzzed out my bought "STAGE LINE" MIDI cables & theres only 3 wires.
I would expect that to be the norm for current day, engineered to a price, cables.

5 pin DIN audio cables should have all wires connected.

[Sam Spoons]

You may well be right these days, I bought a few 'midi' cables back in the day and they all had all 5 pins connected, maybe in anticipation of 'midi mk2'?

[ef37a]

I have no knowledge of the gear involved but would like to make a few observations?

First off, I don't think "Phantom Power" is the correct term here? PP would imply +9V on BOTH pins 1 and 3 ref ground (P2) . I am sure you mean + 9V and zero? Polarity?

Yes, pins 1 and 3 could well be connected to something that would mind 9 volts but most likely O/C or connected to chassis/ground.

Safest way IMHO is a break out box so that the 9V only goes to the the device it is intended for.

How much current is required? "Switching" as a control usually need but micro amps, if a LED is involved a few mA. You want the supply to be S/C proof ('it'appen) so use current limiting resistors.

Dave

[N i g e l]

How much current is required? "Switching" as a control usually need but micro amps, if a LED is involved a few mA. You want the supply to be S/C proof ('it'appen) so use current limiting resistors.

Dave

"approx 15mA". It has a 2 1/2 digit LED display with "screen saver mode"

[ef37a]

How much current is required? "Switching" as a control usually need but micro amps, if a LED is involved a few mA. You want the supply to be S/C proof ('it'appen) so use current limiting resistors.

Dave

"approx 15mA". It has a 2 1/2 digit LED display with "screen saver mode"

That is not an insignificant current so I would use a 12V supply and one of these...https://www.elfadistrelec.pl/en/linear- ... p/17300123

Gives a very clean 9 volts with short circuit protection.

Dave.

[Sam Spoons]

I just used the unused pins 1 & 3 conductors as an extension from the original PSU...

[DC-Choppah]

I have no knowledge of the gear involved but would like to make a few observations?

First off, I don't think "Phantom Power" is the correct term here? PP would imply +9V on BOTH pins 1 and 3 ref ground (P2) . I am sure you mean + 9V and zero? Polarity?

Yes, pins 1 and 3 could well be connected to something that would mind 9 volts but most likely O/C or connected to chassis/ground.

Safest way IMHO is a break out box so that the 9V only goes to the the device it is intended for.

How much current is required? "Switching" as a control usually need but micro amps, if a LED is involved a few mA. You want the supply to be S/C proof ('it'appen) so use current limiting resistors.

Dave

The foot pedal says that it needs 8-15 VDC with any polarity, and 100 mA.

[N i g e l]

Ive just buzzed out my bought "ssnake" 9m MIDI cable [from Thomann] & surprised to find that all 5 pins are wired up. max current spec unknown.

[ef37a]

Ive just buzzed out my bought "ssnake" 9m MIDI cable [from Thomann] & surprised to find that all 5 pins are wired up. max current spec unknown.

From RS Comps' : 100V 2A per pin. That is for top quality and connector only so 1 amp easy for a cable?

Dave.

[N i g e l]

thats for the DIN pins tho ? what about the wires in the cable. MIDI is a 5mA current loop but Mr Choppah wants to put 100mA power down there. Probably ok for voltage drop ?

[BillB]

If it is any help, the manual states:

“PHANTOM” POWER OPERATION VIA MIDI CABLE
The MIDI Mouse will accept power via a standard 5 conductor/pin MIDI cable through Pins 1 and 3. Consult the owner’s manual of your processor for its phantom power support capabilities and specifications.
NOTE: Power must be between 8 and 15V DC, any polarity.

There is also a little pin-out diagram. I was surprised at the 'any polarity' part.

[ef37a]

thats for the DIN pins tho ? what about the wires in the cable. MIDI is a 5mA current loop but Mr Choppah wants to put 100mA power down there. Probably ok for voltage drop ?

Ooo! Any wire a bit thicker than a human hair will cope with 100mA I think (look at the wire in a 1A glass fuse?)

Voltage drop? You need a fair bit of 'signal sized' wire to get even one Ohm so that would be 0.1 volts AKA naff all. If you have 'buzzed out' the cables you could try to measure their resistance but I bet it is so low you won't get a reliable reading on a stock DMM?

Dave.

[James Perrett]

II was surprised at the 'any polarity' part.

I guess they've gone to the expense of putting a bridge rectifier on the power input.

[BillB]

II was surprised at the 'any polarity' part.

I guess they've gone to the expense of putting a bridge rectifier on the power input.

My rudimentary understanding of electronics made me think that a bridge rectifier was for converting AC to DC. Didn't know one could be used for converting +/- DC to +DC.
Clever stuff. Why doesn't everyone do it? - no more fried DC inputs after wrong polarity 'experiments'

[Hugh Robjohns]

Why doesn't everyone do it? - no more fried DC inputs after wrong polarity 'experiments'

Because it adds to the build cost. It requires physical space on the circuit boards, it consumes some energy and loses some volts... and because most people are intelligent enough to use the right power supplies with the right devices.

[ef37a]

II was surprised at the 'any polarity' part.

I guess they've gone to the expense of putting a bridge rectifier on the power input.

My rudimentary understanding of electronics made me think that a bridge rectifier was for converting AC to DC. Didn't know one could be used for converting +/- DC to +DC.
Clever stuff. Why doesn't everyone do it? - no more fried DC inputs after wrong polarity 'experiments'

The answer you might know. cost. Yes a wee 1 amp bridge rectifier might be less than 50p but the beancounters always have an eye on the competition.

There is also a technical reason, you are putting extra diode volt drops in the DC feed which means the upstream voltage has to be a bit higher and more volts means more money...again!

Hi Hugh, we crossed qwertys with the same story. Not sure I agree with "Most people are smart..."!!

Dave.

[BillB]

Because it adds to the build cost. It requires physical space on the circuit boards, it consumes some energy and loses some volts... and because most people are intelligent enough to use the right power supplies with the right devices.

Thank you both.
Obviously it was the other poor stupid people I was thinking of