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

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

Postby BillB » Thu Oct 22, 2020 6:20 pm

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

Postby ef37a » Thu Oct 22, 2020 6:22 pm

N i g e l wrote: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?

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

Postby James Perrett » Thu Oct 22, 2020 10:03 pm

BillB wrote: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.
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Re: Adding Phantom Power to MIDI cable from Lexicon MX200 to remote footswitch for program change?

Postby BillB » Fri Oct 23, 2020 3:15 pm

James Perrett wrote:
BillB wrote: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' :beamup:
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Re: Adding Phantom Power to MIDI cable from Lexicon MX200 to remote footswitch for program change?

Postby Hugh Robjohns » Fri Oct 23, 2020 3:43 pm

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

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

Postby ef37a » Fri Oct 23, 2020 3:47 pm

BillB wrote:
James Perrett wrote:
BillB wrote: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' :beamup:

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..."!!

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

Postby BillB » Fri Oct 23, 2020 3:49 pm

Hugh Robjohns wrote: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 :headbang:
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