Scaling a midi expression pedal

Hi guys,

Firstly - thanks for a great product and outstanding customer service!

So, I'm trying to use my Yamaha FC7 MIDI expression pedal with Ableton Live suite 10, via Bome Translator Pro.

The pedal has a 50k pot in there and should be replaced with a 10k pot but after seeing 2 repair/ mod guys, it's proving difficult to access the part to do the mod. I'm wondering if Bome can fix the problem.

The Problem is, if you step on the pedal from heel to toe, the midi message goes from min to max at not even half of the pedals full sweep range, meaning the latter 'toe-down' half does nothing as the midi message has already reached 127 when the rocker was halfway between heel and toe.

Any ideas? Thank you so much!

 

Kind Regards,

Benji M

Interesting, Benji, since I don’t think the FC7 sends MIDI at all. You must be running it analog through a CV to MIDI converter or a keyboard.  Can you provide more details on how you have it connected?

 

In the mean time you can certainly look at our tutorial on scaling.

Steve Caldwell
Bome Q and A Moderator and
Independent Bome Consultant/Specialist
bome@sniz.biz

P.S. Thank you for the kind words!

Also, the issue may not be the pot, yet the way it is wired. Different manufactures tie the wiper to a different connector on the TRS connector. See below:

https://www.soundonsound.com/forum/viewtopic.php?f=35&t=800#8037

Steve Caldwell
Bome Q and A Moderator and
Independent Bome Consultant/Specialist
bome@sniz.biz

Hi, see if your technician can just swap the tip and ring connects to the pot inside. I’m about 90% sure this will solve the problem.  If you don’t want to mod your pedal, get a couple stereo splitters as below and and connect red to black(or white) on the RCA end.

https://www.amazon.com/gp/product/B000068O5C/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B01CG4C7FS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

The cables or rewiring will simply swap the wiper connection with the Hot connection.

The pot value really will not have much relevance here. 10K to 100K should be fine.

See attached picture for use of cable for reversing tip and ring.

Benji, Did you resolve your problem? I’m pretty sure Bome can’t fix this. My FC7 pedals connect directly to my Yamaha products. I’d recommend changing the pot. One thing about original Yamaha MIDI products, like the 1st DX7, and probably the DX5, Yamaha screwed up and set the MIDI Vol to 0-100, instead of 0-127. Of course this CAN be fixed by Bome’s MT. Duhhhhh… Bad me….I forgot to mention, I’m not sure if the pots in my Yamaha pedals are exponential or linear. Makes a BIG difference. Check yours!! (I’m guessing they should be linear in this case….I’ll go check. In an audio amp pots are exponential….the way your ear responds. In MIDI…..pots are linear)

Thanks @SirLanceAlot! Unless this is a really old FC7, the pot should be linear. Before replacing it, I would rewire it as in the reverse position it will either not work at all or be EXTREMELY non-linear
(depending of the value of the POT). In the right terminal configuration, the POT value will not matter as much except perhaps on the EV5 which has an additional trimming (calibration) POT.

Having the wrong wiring puts the POT in a parallel configuration with whatever other resister might be used within the keyboard (or other device) that you are connecting.

Personally, I don’t like to solder which is why I went with the cable reversing solution. Also with the cable I can remove it to us my Hammond pedal with my Hammond SK2, and hook it back up to use with my Korg PA900, This cost about $15 which is less expensive than another expression pedal and less than having to pay a service tech the labor involved.

Once you get a full range of motion of the POT (MIDI Message continue through the full range of motion) , then we can look the resulting MIDI if necessary to make tweaks to the linearity.

Steve Caldwell
Bome Q and A Moderator and
Independent Bome Consultant/Specialist
bome@sniz.biz