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Midi MuRF in patchbay

Posted: Sun Aug 14, 2011 4:18 pm
by PHC
Hi

I've just put my 105M in a rack and connected it to a TRS patchbay (with a TRS cable) and there is a problem.
All my other racked foogers (101, 102, 103, 107) behave correctly (knobs work full range as if there were no cables pluged into the foogers - except some normalling that had to be done in the 102 and 103), but 105M is different.

When I plug the cables the knobs stop functioning or function in a very narrow (low) range. I guess it's like I've plugged an "empty" expression pedal, but it doesn't add to the knob setting, it just drops the value of the knob to the low range. When I plug somthing into the patchbay (eg. lfo) it controls the 105M correctly, it's just the empty patch cable into patch bay that causes problems. Any solution?

Re: Midi MuRF in patchbay

Posted: Sun Aug 14, 2011 11:18 pm
by jeepo
You could try using jacks normalled such that when nothing is plugged in they send a couple volts to the tip.

Re: Midi MuRF in patchbay

Posted: Mon Aug 15, 2011 3:44 am
by PHC
Now how do I do that?

I understand that it will fool the murf that an expression pedal in the heel position is plugged in?

Re: Midi MuRF in patchbay

Posted: Tue Aug 16, 2011 1:03 am
by jeepo
I think your unit is functioning as though it has a expression pedal plugged in. If I plug an expression pedal in its heal position into the rate jack of my murf it slows down. To counter this I would normal the jack to a voltage divider so that it acts like an expression pedal is plugged into the jack somewhere within its range when nothing is plugged in. I would start by using two 25k-ish resistors to build the following circuit (I was gonna attach it, but I don't know how, PM me if you want me to email it to you) then increase or decrease the resistor connected to ground to adjust the voltage.

Re: Midi MuRF in patchbay

Posted: Fri Aug 19, 2011 3:26 am
by PHC
Why am I having no issues like that with my other MFs? How is the MuRF different? (I guess something about how it handles the knob values to make it MIDI comaptibile).

Re: Midi MuRF in patchbay

Posted: Fri Aug 19, 2011 10:28 am
by Sir Nose

Re: Midi MuRF in patchbay

Posted: Fri Aug 19, 2011 12:19 pm
by PHC
Thanx. I must say that's really a bad solution. They should put some jumpers inside that might change the behaviour. Many people rack their foogers and it's really not up their alley. So I guess there is no solution (I don't know if a 2.5V normalling in the patchbay would solve this?)