Poorly implemented EXP-2 expression pedal - CV control

roger2600 · Post by **roger2600** » Fri Dec 14, 2012 5:24 pm

Thanks you guys, yes I understand the problem and know electronics very well as i am an electrochemist by day. The EXP-2 pedal I have is brand new and I did not feel like opening it and modifying it. What seapea means by swappint the pots does not mean changing the polirity, he means he took the tree wires solderd to one potentiometer and swapped them with the three wires soldered to the other potentiometer. My question is more related to what all Korg CV pedal inputs are looking for. If the 90K pot works on a Kronos properly (I still don't believe it does actually) than why not on all Korg instruments. Like I said they have been using the same pedal since the M-1 you would think it would work exactly the same on all Korg products. I believe you guys. I believe the Krome wants to have a 50K linear pot (I will find out soon when the Yamaha pedal comes in.

As far as my EXP-2 is I am certain of my findings. the jacks meant for audio is 0 to 48K linear and the slider on the side adds 50 K to everything when at 10. I agree this sounds wrong for an audio pedal and I never tried it for audio. The output 2 was 90 K and i did not make a graph of it but it seems log.

What I want Korg to do is report the specification of the EXP-2 so I and they would know if China is making the pedal wrong. Then I would like them to tell me what the Krome (and all Korg keyboards) specifications are that make the cc values go from 0 to 127 properly (hopefully all are the same???). This stuff should not be of a proprietary nature i wouldn't think so why not report it?

seapea · Post by **seapea** » Fri Dec 14, 2012 6:39 pm

.Jens wrote:[. But I would be still interested if your pedal now still works correctly in the audio path. If so, the only logical conclusion would be, that by swapping and re-soldering the pots you also corrected the wiring of the expression pot - intentionally or not
...

Hi Jens. I had not bothered to reconnected the audio path, in/out 1, as I never use this, but in the name of science and world peace

, I whipped off pedal's bottom, and reconnected. Result was as you suspected, was not a truely "linear" increase in volume. There was still not as much level increase in 2nd half of travel, as in first half, but still significantly more increase than experienced using this 90K pot as the expression controller. So for me, using the linear 50K pot for expression, works just like a Yamaha FC7. Cheers

.Jens · Post by **.Jens** » Sat Dec 15, 2012 12:08 am

roger2600 wrote:hat seapea means by swappint the pots does not mean changing the polirity, he means he took the tree wires solderd to one potentiometer and swapped them with the three wires soldered to the other potentiometer.

Yes, I think I got his point - I just assume that by doing this, at the same time he may have corrected an additional error. But we'll never know - it doesn't matter anyways.

My question is more related to what all Korg CV pedal inputs are looking for.

It's the way I wrote earlier: "Expected" is a linear pot with sleeve and tip wired to the "ends" of the pot and the ring connected to the slider. Resistance values don't really matter, as long as they are in the kOhm-range. I have successfully tested pedals from 10k to 100k - they all work the same. So practically all available models should work, as long as they are linear and wired as above.

One remark: To avoid confusion, you should note that a CV pedal and an expression pedal are not the same technically, even if they serve similar purposes. Maybe that could be part of misunderstandings, but CV pedals usually are "active" (with their own power supply), and delivering a voltage of typically 0...10V to the synth (single ended). Older (passive) "swell" pedals - often called CV pedals as well - had a single ended output, too; and that's the point where the resistance value matters (because the counterpart for the voltage divider is built into the synth). Expession pedals all have three "pins", and all are required to make them work correctly.

If the 90K pot works on a Kronos properly (I still don't believe it does actually) than why not on all Korg instruments.

It does. It works on the Kronos and will work on M1, M3, Krome... The only reason that your pedal doesn't work on your Krome (and M1) is that either your pedal is wired incorrectly (which I assume), or there is something wrong with your cables.
Believe me, it makes no sense that Korg recommends the same pedal for all their products and change their specification. When my EXP2 works on all Korg gear I had ever tested, and your EXP2 doesn't work on all your Korg gear, then both our pedals are obviously different.

I agree this sounds wrong for an audio pedal and I never tried it for audio.

There is no "right" or "wrong" regarding lin or log for audio. Both kinds work, there are models for both types available and finally this is just a matter of taste.

The output 2 was 90 K and i did not make a graph of it but it seems log.

Just two questions: 1) you measured between which 2 pins? There are three possible pairs on a TRS jack... 2) When you say "log" - this should make either around 22k or 68k on the pair you chose for your measurement, when the pedal is in middle position. Was it more like 22 or more like 68?

What I want Korg to do is report the specification of the EXP-2 so I and they would know if China is making the pedal wrong.

Well, an official spec would be helpful, agreed. But if yours is made in China, I think you own a fake. All the genuine Korg pedals I know are made in Japan...

.Jens · Post by **.Jens** » Sat Dec 15, 2012 12:15 am

seapea wrote: Hi Jens. I had not bothered to reconnected the audio path, in/out 1, as I never use this, but in the name of science and world peace , I whipped off pedal's bottom, and reconnected.

Wow, thank you - that's what I call commitment

Result was as you suspected, was not a truely "linear" increase in volume. There was still not as much level increase in 2nd half of travel, as in first half, but still significantly more increase than experienced using this 90K pot as the expression controller.

What you describe sound perfectly normal to me when using a linear pot on an audio path. If the perceived nonlinearity on the audio part is now less than on the expression part before, you definitely changed the wiring "on top" of changing the pots. If you just had swapped a log vs. a linear pot as you wrote, the perceived nonlinearity on the audio part would be stronger... But that's good to know, as (in my opinion) the case is rapidly narrowing down to a QC issue at Korg's manufacturing site - just two misplaced wires...

danatkorg · Post by **danatkorg** » Sat Dec 15, 2012 12:36 am

roger2600 wrote:As far as my EXP-2 is I am certain of my findings. the jacks meant for audio is 0 to 48K linear and the slider on the side adds 50 K to everything when at 10. I agree this sounds wrong for an audio pedal and I never tried it for audio. The output 2 was 90 K and i did not make a graph of it but it seems log.

What I want Korg to do is report the specification of the EXP-2 so I and they would know if China is making the pedal wrong. Then I would like them to tell me what the Krome (and all Korg keyboards) specifications are that make the cc values go from 0 to 127 properly (hopefully all are the same???). This stuff should not be of a proprietary nature i wouldn't think so why not report it?

In general, I cannot discuss technical details which are not already available to the public. This is a support issue, and the way to communicate with Korg about such things is to contact your Korg Distributor. They should be glad to help you!

The other thing to note is that, with A/D inputs like pedals etc., calibration is usually required. It's always possible that the keyboard needs to be re-calibrated. For the KRONOS this would require service; I don't know about the KROME, but again your Korg Distributor should know.

Dan

roger2600 · Post by **roger2600** » Sat Dec 15, 2012 1:28 am

Well I recieved the Yamaha FC7 today:
1. It works perfectly as a foot pedal should on a keyboard; 0 at bottom, 64 at 1/2 and 127 at full, very linear, feels nice.
2. The build quality of the FC7 is at least twice as good as the EXP-2 Not even close.
3. The Sweetwater cost of the FC7 is 49.99 and the EXP-2 is 69.99.
4. Korg has issues I hope they correct, I like Korg but they got spanked by Yamaha on this one.
5. If anybody out there wants to plug a foot pedal into a Korg, buy the FC7. I recommend it totally over EXP-2.

O.K. finally I will let it go now, sorry for being a prick. You forum guys helped me a lot on this one.

bobco631 · Post by **bobco631** » Mon Jan 07, 2013 2:03 am

I've had an EXP-2 for like ten years, never worked satisfactorily, exp vol was like 45 to 90, swapped the three wires from one pot with the next, side by side like they are, tested it, and voila! 0 to 127! Great, thanks for the suggestions!

craigx · Post by **craigx** » Thu Jan 10, 2013 4:19 am

I already posted my question somewhere here in the forums and got an answer from an awesome member. However that didn't get me to fix my prob. I just want to ask what kind of cable should i use for my korg ps60 when using boss fv500l exp pedal? As of now im using trs and its not working.

danatkorg · Post by **danatkorg** » Thu Jan 10, 2013 4:24 am

roger2600 wrote:Well I recieved the Yamaha FC7 today:
1. It works perfectly as a foot pedal should on a keyboard; 0 at bottom, 64 at 1/2 and 127 at full, very linear, feels nice.
2. The build quality of the FC7 is at least twice as good as the EXP-2 Not even close.
3. The Sweetwater cost of the FC7 is 49.99 and the EXP-2 is 69.99.
4. Korg has issues I hope they correct, I like Korg but they got spanked by Yamaha on this one.
5. If anybody out there wants to plug a foot pedal into a Korg, buy the FC7. I recommend it totally over EXP-2.

O.K. finally I will let it go now, sorry for being a prick. You forum guys helped me a lot on this one.

Note that the EXP-2 also works as an analog volume pedal, audio in to audio out. The FC7 is nice too, but it works only as a control signal generator.

.Jens · Post by **.Jens** » Thu Jan 10, 2013 9:18 am

craigx wrote:I already posted my question somewhere here in the forums and got an answer from an awesome member. However that didn't get me to fix my prob. I just want to ask what kind of cable should i use for my korg ps60 when using boss fv500l exp pedal? As of now im using trs and its not working.

If I am right assuming that all Korg instruments require the same specs for expression pedal, then a TRS cable with the wiring of tip and ring swapped on one end should do the job. At least that did the trick for me with the Kronos and exactly the same pedal (Boss FV500L).

craigx · Post by **craigx** » Thu Jan 10, 2013 11:47 am

.Jens wrote:
craigx wrote:I already posted my question somewhere here in the forums and got an answer from an awesome member. However that didn't get me to fix my prob. I just want to ask what kind of cable should i use for my korg ps60 when using boss fv500l exp pedal? As of now im using trs and its not working.
If I am right assuming that all Korg instruments require the same specs for expression pedal, then a TRS cable with the wiring of tip and ring swapped on one end should do the job. At least that did the trick for me with the Kronos and exactly the same pedal (Boss FV500L).

Thanks, Jens! Im gonna try your suggestion... I would just like to point out that my boss fv500l works well with my korg x5d using a regular TRS cable... Thank you!

.Jens · Post by **.Jens** » Thu Jan 10, 2013 11:52 am

craigx wrote: Thanks, Jens! Im gonna try your suggestion... I would just like to point out that my boss fv500l works well with my korg x5d using a regular TRS cable... Thank you!

I'd bet it will work even better with a crossover cable - give it a try. Mine "worked" with a regular TRS on the Kronos, too, but the response was rather nonlinear...

craigx · Post by **craigx** » Sat Mar 02, 2013 6:54 am

Greetings! Took long but i finally tried the crossover cable. had a hard time calibrating the pedal, when successfully calibrated, everything's working fine. However, i have to repeat the calibration everytime i turn off my ps60...i dont think my input jack is broken, it works fine when i use it as switch/sustain... Thanks

rs.felicio · Post by **rs.felicio** » Fri Sep 12, 2014 3:38 pm

Guys,

Is there any Kronos user with experience with Moog EP-3 Expression Pedal?
I´m comparing EV-5, EXP-2, FC-7 and EP-3 and Moog looks like a heavy option for a good price.

Thanks

Puptentacle · Post by **Puptentacle** » Tue Feb 07, 2017 12:33 am

.Jens wrote:
roger2600 wrote:hat seapea means by swappint the pots does not mean changing the polirity, he means he took the tree wires solderd to one potentiometer and swapped them with the three wires soldered to the other potentiometer.
Yes, I think I got his point - I just assume that by doing this, at the same time he may have corrected an additional error. But we'll never know - it doesn't matter anyways.

My question is more related to what all Korg CV pedal inputs are looking for.
It's the way I wrote earlier: "Expected" is a linear pot with sleeve and tip wired to the "ends" of the pot and the ring connected to the slider. Resistance values don't really matter, as long as they are in the kOhm-range. I have successfully tested pedals from 10k to 100k - they all work the same. So practically all available models should work, as long as they are linear and wired as above.

One remark: To avoid confusion, you should note that a CV pedal and an expression pedal are not the same technically, even if they serve similar purposes. Maybe that could be part of misunderstandings, but CV pedals usually are "active" (with their own power supply), and delivering a voltage of typically 0...10V to the synth (single ended). Older (passive) "swell" pedals - often called CV pedals as well - had a single ended output, too; and that's the point where the resistance value matters (because the counterpart for the voltage divider is built into the synth). Expession pedals all have three "pins", and all are required to make them work correctly.

Just wanted to say thanks a million .Jens for the tip about crossover cables. I can confirm that the BOSS FV-500L expression pedal also needs a crossover TRS cable to function with the Korg M3 workstation.

Less than two minutes work with a soldering iron to swap ring and tip on one end.
You the real MVP

Korg Forums

Poorly implemented EXP-2 expression pedal - CV control

Re: To Jens:

Re: To Jens:

swapped the EXP-2 wires and voila!