Topic by houston

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Topic: Sustain pedal polarity reverse

For years I've been using a simple on/off sustain pedal with my SL-990 controller. Finally decided to upgrade to a full-range pedal, and picked up a good deal on a Yamaha FC3A. I considered to pick up an AudioFront MIDI Expression, as it seems they will accept anything. But first, decided to give it a try it with the expression input on my old Kurzweil K2000. Then it's just a matter to insert the K2000's midi between the Fatar and the PC.

As mostly expected, it's in reverse: pedal up = full sustain, and pedal down = no sustain. I made a few attempts to power cycle the K2000, to see if it would readjust, but seems not to work.

The good news is that PTQ of course allows for a reversal, and together with the curves, I'm able to get it working just fine (and the old pedal defaulted to "soft", which is great). Except for one thing: the graphic of the 4 pedals still shows the pedal in reverse. Not a huge deal, but a bit distracting! Shouldn't reversing the pedal also reverse the graphic? Instead it shows the pedal normally down, even though the sound is with the pedal up.

It still would be more convenient for the pedal to work natively with the Kurzweil. Is it as simple as reversing the Tip and Ring on the plug? I planned to quickly build a simple adapter to try this (certainly it won't harm anything), but spent a bunch of time only to find out that I have dozens of mono 1/4" cables and plugs and jacks around, but almost nothing for stereo (TRS).

So if anyone is fairly sure that switching T and R will do the trick, then I'll pick up (completed or parts for) an adapter. Thanks!

Reply by Beto-Music

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Re: Sustain pedal polarity reverse

I remamber something about a progressive pedal of one brand fit to another brand, if a polarity change, or something easy and fast on circuit, was performed.

There was a video about...

I think it was this sort of procedure or a similar:

https://www.youtube.com/watch?v=Oi0TNTsR7OE

Last edited by Beto-Music (08-12-2020 02:23)

Reply by houston

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Re: Sustain pedal polarity reverse

Thanks @Beto-Music

In this case it would be a pot rather than a switch, and rewiring the pot is something I've been looking into as well (I need Normally Open rather than the current Normally Closed). However, if a simple adapter can do the same thing (which may very well not be the case, but would like to explore that first)...

Last edited by houston (08-12-2020 05:26)

Reply by houston

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Re: Sustain pedal polarity reverse

Ok, I figured it out. With the help of a TRS insert cable and 3 stripped hookup wires, first I tried switching the Tip and Ring. However that didn't seem to change anything. Then I opened up the pedal and noticed it's simply a single 10k pot, apparently wired as Sleeve on one side, Ring in the middle, and Tip on the other side. So I closed it back up, with the idea that it's those 2 outside leads that we care about. So I tried my loose wires again, this time with Sleeve and Tip reversed. Et voila!

So I can either order the parts to switch the Tip and Sleeve, or simply open it back up and re-solder them. Either way will be doing the exact same thing electrically. And since it's just the single, passive pot inside, rewiring internally would be extremely easy. As would building an adapter.

Reply by Stephen_Doonan

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Re: Sustain pedal polarity reverse

I also have a Yamaha FC3A pedal. There are several brands (such as Nektar and OnStage) of simple-switch sustain pedals (not half-damper capable) that include a polarity switch to exchange their tip-sleeve cable electrical signal, but wasn't able to find the same functionality for a tip-ring-sleeve half-damper capable pedal (a pedal which produces a range of electrical values that are interpreted or translated by the keyboard into MIDI continuous CC numerical values,  instead of being just an on/off momentary switch).

So after reading about the issue somewhere online, I just opened up the Yamaha FC3A, unsoldered the wires of the potentiometer, then switched and resoldered them. Simple fix; worked great.

Last edited by Stephen_Doonan (08-12-2020 15:42)
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Reply by houston

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Re: Sustain pedal polarity reverse

Thanks @Stephen_Doonan

The issue though is figuring out which wires to switch. There are plenty of "polarity reversing adapters" (short female-to-male 1/4" stereo cables) out there, but they all seems to switch T and R. Wouldn't it be unfortunate to spend $20-30 and a week's wait, only to find out it doesn't work?

So far I don't think I any of the adapters I saw were TRS to SRT.

And again to request to Modartt that it's great we're able to reverse the pedal in software, but please also reverse the on-screen pedal graphic to match it. Thank you!

Reply by Stephen_Doonan

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Re: Sustain pedal polarity reverse

houston wrote:

The issue though is figuring out which wires to switch.

After opening up the pedal and unsoldering the wires on the potentiometer, I believe that I connected the pedal's cable to my keyboard, and my keyboard's USB MIDI output to the computer, where I used a MIDI monitor (Pianoteq has one in its Options-->MIDI panel, but I more frequently use the app MIDIsnoop in Linux) to check the MIDI output of the pedal-and-keyboard as I moved and held the wires to different terminals, until the MIDI output matched what I expected and wanted; then I soldered the wires in that position, screwed the pedal and its housing back together, and used the pedal.

It seems to me to be a simpler fix than rewiring the cable or finding and buying a suitable adapter. However, the following TRS polarity switching adapter might work; although it was created to reverse the polarity of an expression pedal such as the Yamaha FC7, because an expression pedal and half-damper-capable sustain pedal both use potentiometers, it might work with the Yamaha FC3A as well.

Beat Bars TRS polarity adapter
https://beatbars.com/en/trs-extension-reversed.html

Edit: actually, this polarity adapter seems to be configured to switch tip-to-ring and ring-to-tip (like the others you found). Sorry.

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Last edited by Stephen_Doonan (08-12-2020 18:06)
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Reply by houston

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Re: Sustain pedal polarity reverse

Stephen, indeed the Beat Bars adapter was one of the more prominent ones I found. It's good that they show the wiring clearly, but most readers (like me 24 hrs ago, which prompted my posting here) may too easily assume this will solve their problem. Seems it should be in the company's interest (and I may write to them about it) to advise known devices it does and doesn't work with. Otherwise, they may have grumpy customers, as well as a lot of returns, which quickly become very expensive for a mfr.

Alternatively, it should be quite straightforward to make an adapter with 2 switches on it: one to switch T and R, and the other to switch T and S. This should then give you all combinations.

Also just to note, afaik a "half pedal capable sustain" like the FC3A really is just an expression pedal. Not in form factor of course, but at least electrically. My Kurzweil synth that I'm happily now using it with has no way to know that the other end of it just happens to look like a piano pedal, rather than a guitar wah / volume pedal or organ swell pedal. So I think it should be able to work with, say, a guitar mutli effects such as my Zoom G5n, which has an extra expression input. Not that there are necessarily practical applications, but perhaps could come in handy if one needed something with far less travel than the standard wah...?