To me it’s a pity that it’s only the sustain pedal that can be configured as a rotary speed switch.
I’d prefer the left pedal for that purpose.
When I installed the enclosed anti-slip rubber I had to remove screws from the bottom of the Triple Pedal which made me curious how the whole thing might work.
So I removed the bottom cover and detached the encasement.
The attached images no. 01 to 05 show how it looks like.
The Triple Pedal doesn’t use simple normally-open-switches for its functions.
It’s got 4 resistors that control the half pedal functionality of the sustain pedal using the tip –> shield part of the TRS-jack and respectively one resistor for each of the other two pedals both using the ring –> shield part of the jack.
The related switches are rubber-mounted graphite stampers that simply connect two conducting tracks on the printed circuit board.
Each switch consists of two stampers that are attached at slightly different levels so that they don’t connect simultaneously.
The sustain pedal has got two of these double switches so that there are 5 operating conditions:
all open to all closed. That means that there are 3 possible half pedal states.
The electrical resistance between the tip and shield connectors goes from infinite (fully open) to something like 10kΩ to 3,2kΩ to 1,3kΩ to 0,5kΩ (which is recognized as no resistance) as you press the sustain pedal down slowly .
The related resistors R1 to R4 can be seen on the images no. 07, 08 and 10.
The middle pedal is wired up to the ring connector via a 10kΩ-resistor (R5).
The left pedal goes also to the ring connector but by a 5 kΩ-resistor (R6).
That’s why a simple open – closed foot switch is not suitable for controlling the Sostenuto and Soft Pedal functionality.
And that’s also the reason why the left pedal can’t control the rotary speed (unless an OS update might implement this) even if you connected the ring connector to the tip of an adapter cable and plugged it into the latch/rotor pedal input.
BUT:
If you bypassed R6 the left pedal could do what I would like it to do.
And that’s exactly what I did:
I soldered a wire onto each side of resistor R6 ( see the red arrows in picture no. 10) that I connected via a flip switch so that I can switch the bypass on and off.
Off means the Triple Pedal works as before, on means the left pedal can switch the rotary speed if connected to the rotor input.
I integrated the flip switch into the top of the Triple Pedal which actually looks as if it was meant to be like this (see pictures 11 to 14).
What you need additionally is a Y-adapter cable that splits the TRS jack into two TS jacks (stereo female to 2x male, e.g. http://www.thomann.de/gb/pro_snake_tpy_2003_bpp.htm ).
The tip-part needs to go to the sustain pedal input, the ring part to the latch/rotor pedal input.
The middle pedal is not in use in that mode.
At the moment I have to change plugs if I want to use the Sostenuto and Soft Pedal again.
So I think I might build a switch box that does that by another flip switch.
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