Custom switcher advice

[IvIark]

Hi to you all

I'm a bit of a lurker here and basically I am making up a second rig consisting of a small rack for a combo amp I'm buying (4U with 2 processors and a rack tray for a couple of pre-amplifier pedals) and wondered if any resident experts could offer a bit of advice.

I want to make a two section switcher which will consist of a 3 button footswitch and a separate remote controller which will be in the rack. This will be setup as follows:

Stomp switch 1: Switch amp channels (2 channel amp only and so just a mono cable will do this)

Stomp switch 2: Energize a relay in the remote controller for a true bypass loop for the rack tray

Stomp switch 3: Remote bypass a rack effect (again as per SS1, just a simple mono cable with the stomp switch shorting between the sleeve and tip)

I want to connect the floor controller to the remote controller with a standard 5 pin MIDI cable (I already have the cable and connectors so it saves me getting a 7 pin connector) but ideally I would need 6 pins, 2 for each stomp switch.

Stomp switch 2 will definitely need 2 of the MIDI cores because I need to bring 9V from the remote controller, go through SS2 and then take it back to the relay, but my question is can I common up the sleeve on SS1 and SS3 and so just require 1 core for both switches? This would be perfect because then it will only use 5 cores of the MIDI cable. Can anyone think of any problems that this may give me? I don't think I have to have everything totally isolated because there is no audio signal passing down the cable and it is all simple control.

Thanks for any advice you can give.

[boogietube]

Here's a link-" remote footswitch bypassing system" from Geofex
http://www.geofex.com/
Also type ASMOP on this site and you'll open a whole new world.
Cheers
Sean

[Seljer]

Why would you need 6 pins?

3 for the on/off signals of each effect
1 for ground
1 for +9V (or whatever voltages the thing would run off)

the footswitches would be regular non-momentary SPDT footswitches, connect the cenre one to the signal, connect the other one 2 ground and +9V (or use DPDTs and use the other half if the switch for LED indicators)

then into the switch box you're getting the 3 signals from the footswitch which are 0V for off and 9V for on, with those you then control the 3 things you're switching

for the bypass loop
http://www.geofex.com/Article_Folders/rmtswtch/rmtsw.htm

the other 2 things could also be done with relays but I think you just as easily get away with a cheap transistor or MOSFET

[IvIark]

Here's a link-" remote footswitch bypassing system" from Geofex
http://www.geofex.com/
Also type ASMOP on this site and you'll open a whole new world.
Cheers
Sean

Thanks but my main rig is all MIDI controlled and this doesn't need to be complicated in anyway, I just need a 3 switch footpedal and the remote box as described.

[IvIark]

Why would you need 6 pins?

3 for the on/off signals of each effect
1 for ground
1 for +9V (or whatever voltages the thing would run off)

the footswitches would be regular non-momentary SPDT footswitches, connect the cenre one to the signal, connect the other one 2 ground and +9V (or use DPDTs and use the other half if the switch for LED indicators)

then into the switch box you're getting the 3 signals from the footswitch which are 0V for off and 9V for on, with those you then control the 3 things you're switching

for the bypass loop
http://www.geofex.com/Article_Folders/rmtswtch/rmtsw.htm

the other 2 things could also be done with relays but I think you just as easily get away with a cheap transistor or MOSFET

I need 6 cores because 2 of the switches aren't going to be switching 9V, they're simply making or breaking a contact between tip and sleeve of a jack in the rack mounted box.

Switch 1 is used for channel switching and so all it is doing is shorting between the tip and sleeve, the relay is in the amp.  2 cores required for the sleeve and tip connection.

Switch 2 will be switching 9V for a relay in the rackmounted box for a true bypass loop.  2 cores required for the 9V feed from the rack box and the return to energise a relay in the rack box.

Switch 3 is used for remote bypass of an effect processor and again all it is doing is shorting between the tip and sleeve, the relay is in the processor.  2 cores required for the sleeve and tip connection.

I know I can do this if I put 3 relays in the rack mounted box and then I would just need 4 cores, 1 to supply the 9V to the footpedal and 3 for each stomp switch, but because switch 1 and 3 are simply shorting across tip and sleeve I was hoping to be able to do it without having to use additional relays, i.e all the switching is done with the stomp switches.  And I can do this if I can common up the sleeve.

Thanks for your input

[Ardric]

This is kinda ugly, but I'll throw it out there anyways.

DIN-5 MIDI cables that I've used have 6 conductors.  5 pins, and the shield.  You could use the shield as your relay gnd.  One end of the relay is connected to +9, the other to the cable pin.  Shorting the pin to shield fires the relay.

Watch for ground loops.  Don't put +9 on the shield, because touching the cable to earth might short out your power supply.  And I suppose some cables won't be shielded and won't work.

For bonus points, use a pinout that won't fry any MIDI ports it's accidentally plugged into. 

[IvIark]

This is kinda ugly, but I'll throw it out there anyways.

DIN-5 MIDI cables that I've used have 6 conductors.  5 pins, and the shield.  You could use the shield as your relay gnd.  One end of the relay is connected to +9, the other to the cable pin.  Shorting the pin to shield fires the relay.

Watch for ground loops.  Don't put +9 on the shield, because touching the cable to earth might short out your power supply.  And I suppose some cables won't be shielded and won't work.

For bonus points, use a pinout that won't fry any MIDI ports it's accidentally plugged into. 

Thanks for the thoughts.  Is it pins 1 and 5 with MIDI that is usually used for phantom power?

[Ardric]

MIDI mostly pins 4 and 5 of the DIN5 connector.  I think the assignment is something like...

MIDI output or thru:
  1       n/c
  2       n/c
  3       gnd or n/c
  4       tx +
  5       tx -
shield  gnd or n/c

MIDI input:
  1       n/c
  2       n/c
  3       n/c or gnd
  4       rx +
  5       rx -
shield  n/c or gnd

The input pins 4 and 5 are basically a resistor and LED.  This allows complete electrical isolation between the devices, so no ground loop hum.  It's ok for pins 4 and 5 to have a big voltage on them relative to the rest of the pins and shield.  It's not ok to have a big voltage between 4 and 5, because you'll kill the LED.

If you use a transistor driver beside the relay, you can have a fair bit of resistance in series with the control wire, which might make things safer.

[IvIark]

Thanks a lot, you're a top man!