Poorly implemented EXP-2 expression pedal - CV control

roger2600 · Post by **roger2600** » Fri Dec 07, 2012 3:54 pm

Years ago I had a Korg T-1 and used the EXP-2 expression pedal with it. The pedal worked very poorly because the CC values it transmitted to the keyboard were all stuffed into the first 1/3 of the pedal and the last 2/3 of the throw on the pedal did almost nothing. Also it was not at all linear. Well sadly they have not done anything at all about this in 20 years. The CV control using Korg's own pedal and their keyboard is a terrible.
1. Korg can you please do a better job.
2. Does anybody know of a way to get a decent response with a CV pedal and a Korg instrument?
3. What do others experience when using the EXP-2 and a Kronos or Krome keyboard?

Thanks, I am a dedicated korg fan who needs better control with CV pedal.

.Jens · Post by **.Jens** » Fri Dec 07, 2012 4:07 pm

Just a few days ago, we had a thread about the same issue with a different pedal (also Korg).
I own a EXP-2 and it works absolutely perfect together with the Kronos. But I know the symptoms you describe quite well from other pedals.

So:
1) make sure you use the correct output of the pedal (OUTPUT 2 - the one with the green ring around it - that's for expression). Do NOT use the "OUTPUT 1" jack of the pedal - this is for analog audio control like an ordinary volume pedal.
2) use a TRS cable ("stereo" / "balanced"), not a standard 1/4" wire with only tip and shaft - you need the ring as well, a normal (unbalanced) guitar/instrument cable will not work.
3) make sure it is wired correctly. Tip has to be connected with tip, ring with ring, shaft with shaft. NO interconnects between tip and ring, ring and shaft etc.

And then - have fun

Scatter · Post by **Scatter** » Fri Dec 07, 2012 4:39 pm

This pedal sucks balls, fullstop. Moving the pedal from fully open to closed only turns the potentiometer about 2 thirds of it's range, meaning that a Linear tapered pot will flat out not work. So instead a Logarithmic pot is used that squashes most of the resistance into the beginning of the sweep and by the time the pedal bottoms out with a third of the pot left there is only something like 1% of the pots resistance left.

Unbelievably, the XVP-10 appears to suffer from this as well.

.Jens · Post by **.Jens** » Fri Dec 07, 2012 4:49 pm

Scatter wrote:This pedal sucks balls, fullstop. Moving the pedal from fully open to closed only turns the potentiometer about 2 thirds of it's range, meaning that a Linear tapered pot will flat out not work. So instead a Logarithmic pot is used that squashes most of the range into the beginning of the sweep and by the time the pedal bottoms out with a third of the pot left there is only something like 1% of the pots resistance left.

Hmmm. I use this pedal for almost 20 years now, a lot of synths, including the Kronos, and never had trouble with it. It has exactly the range and linearity I would expect, if you use the right cables and jacks.

However, the pedal behaves exactly like you describe it, if I use the wrong jack, a "mono" cable instead of a "stereo" one, or a cable with tip and ring swapped.

It may be true that there is a log pot (I have to check back at home, I recently measured it...), but if so, this is compensated within all the equipment I ever used.

Anyway, if I push the pedal half way down, I get expression CC values around 60 (as expected), ranging from 1 or 2 (essentially zero) to 127 at the extreme positions...

Unbelievably, the XVP-10 appears to suffer from this as well.

If the XVP-10 behaves like the EXP-2 when operated as intended, there is little to complain about.

Scatter · Post by **Scatter** » Fri Dec 07, 2012 5:06 pm

Welp, case closed. These pedals are a spendid feat of engineering prowess and everyone should buy one.

.Jens · Post by **.Jens** » Fri Dec 07, 2012 5:17 pm

Scatter wrote:Welp, case closed. These pedals are a spendid feat of engineering prowess and everyone should buy one.

No need to be sarcastic. I do not doubt that you don't like them, if for a reason or not. I can only share my experience, which differs from yours.

But I doubt that the R&D at Korg are idiots, and I also doubt that can build synths like the Kronos and Oasys and many more and are not able to design a simple pedal. You have to admit that it is much more probable that mistakes made by users lead to strange results, especially when others use the same equipment without problems.

I have had so many volume pedals under my feet over the years, almost every notable brand, including the built in swell pedals of Hammonds and other organs. The Korg pedals I had did not behave strange (in terms of range and linearity) or in any way different that other brands.

However, I agree that the EXP2 is too small, too lightweight and looks cheap - that's why I changed to a sturdier one. But despite I had never expected it to last that long, it's still alive after 20 years and hundrets of gigs.

.Jens · Post by **.Jens** » Fri Dec 07, 2012 8:04 pm

Just to state a few facts, to whom it may concern:

My EXP-2, which I bought new stock and never changed anything of the inner parts, has two pots (or more precisely a double layer pot, I think - I did not open it this time):
- One 50k linear pot for the audio signal path (IN-OUT1), which always reads 50kOhms on the IN jack, and ranging from 0k to about 47k over the pedal throw, middle position 26k (it's a bit difficult to find the exact half) - so: linear.
- The expression part (OUT 2) has a 90k linear pot, where tip (3) and sleeve (1) are the outer contacts (reading a constant 90k between those two), and the sliding contact goes to the ring (2). Again, middle position is about 47k.

This pin assignment is what Korg instruments "expect" as input. My Boss pedal, btw, is also linear with a 10k pot plus the adjustment knob, which is a 50k linear pot in series - works the same, even with the differing resistance values (as well as every other expression pedal with linear pots). Only difference: Roland/Boss have the sliding contact at the tip instead of the ring - compatibility can be achieved with a crossover cable.

If it comes to MIDI CC mapping, the EXP-2 connected to the Kronos gives CC#04 values (I configured the external pedal as CC#04, "foot pedal") ranging from 0 to 127, middle position yields around 60-70. The only nonlinearity I have found is that the last 5-10% of the throw (just before fully depressed / "flat") don't have an action - 127 is reached at about 90-95% travel. IMO that's better this way than being stuck with 120 or so in the dead stop.

If I swap tip and ring (I have a crossover cable in the toolbox for the Boss pedal), I get the steep increase within the first 1/3 of the throw, and more or less nothing beyond that point. So, my conclusion would be - if it doesn't work as expected, change the cable pin assignment and see if it works.

At the end, here's a list of expression values, taken from http://acapella.harmony-central.com/sho ... Pot-Values :

Bespeco VM18L - 20k
Boss FV-500 - 10k linear (expression pot)
Boss EV-5 - 10k linear
Boss EV-7 - 10k linear ("extra range" pot adds up to 50k ohms)
Boss FV-50L - 50k linear
Ernie Ball VP jr. (active) - 25k log
Ernie Ball VP jr. (passive) - 250k log
Korg EXP-2 - 50k linear
Kurzweil CC-1 - 20k linear
Line6 EX-1 - 10k linear
Mission EP-L6 - 10k linear
Moog EP-2 - 50k linear (reducable)
M-Audio EX-P - 10k linear
Pigtronix EP-1 - 20k
Proel Volume Pedal - 100k linear
Roland RV-5 - 10k linear
TC Electronic X1 - 25k log

danatkorg · Post by **danatkorg** » Fri Dec 07, 2012 10:04 pm

Thanks to Jens for the excellent and detailed explanations and suggestions!

I'll add that, if anyone is still having difficulties after reading the above, your national Korg Distributor (see my signature) should always be happy to help you to get up and running quickly. Talking with someone in real-time is often the fastest way to find a solution. Give them a call and let them assist you!

levioter · Post by **levioter** » Fri Dec 07, 2012 10:29 pm

Thanks Jens for you detailed info !
As always you are cristal clear !

I cannot understand why some guys are sarcastic about your answers !
I will not go further to avoid any polemic !

Thanks again.

Cheers

roger2600 · Post by **roger2600** » Sat Dec 08, 2012 7:01 am

I have the correct cable, it came in the box. I have owned a Korg T-1, an N1, a Triton Le and now I own a Krome. Everyone of the keyboards with the EXP-2 have had this same response (or similar). The reason I posted on the Kronos forum is because I knew I would get better responses than on the Krome forum. This pedal may indeed work correctly with the Kronos. I can assure you it does not work very well at all with all of the keyboards listed above and I just bought both the Krome and the EXP-2 pedal, both are brand new. I am using the supplied orange cable. There is no way the middle of the throw is 60 - 68 not even close (I used the sequencer to check with many tests) and I am of course plugging it into the correct jack, it doesn't even work with the other jacks. It definately does not work properly and I am sure the Korg guy who answered this post can verify this easily. I believe you if you say it works with the Kronos but it does not with the Krome (or the other keyboards I mentioned). 1/2 way up is about 115 and then it goes to 127 by 70% up

Mr. Korg guy can you please do some tests and report back here about the EXP-2 and the Krome?

.Jens · Post by **.Jens** » Sat Dec 08, 2012 11:09 am

Well this is definitely strange. Did you measure the resistance values? Corresponding to all references I found on the net the EXP-2 has a linear pot and therefore should work properly with all Korg synths (mine at least did as well with a Triton Extreme some years ago).

The only reason I can imagine is that there are some EXP-2 out in the field which have log instead of linear pots. Might be a batch released with the wrong pot inside, might be a fake product?

But we are definitely talking about this product?

Korg EXP2

Does yours have "made in japan" engraved on top of the chassis, below the heel end of the upper plate, and a metal baseplate mounted with 6 screws from the bottom?

geoelectro · Post by **geoelectro** » Sat Dec 08, 2012 2:10 pm

I use an Alesis F2. Had great service from it. Used it with my Triton Pro for both the Triton and my Software synths. Now, using it with my Kronos 61.

It works both as a pass-thru volume or as a voltage pedal with a TRS cable.

JPWC · Post by **JPWC** » Sat Dec 08, 2012 3:24 pm

I have two EXP-2's, both work fine, but they are not smooth high quality pedals I's hope they'd be.

Sound like the OP needs to return his pedal or just give up and use the roland D-beam as their CC device.

.Jens · Post by **.Jens** » Sat Dec 08, 2012 5:03 pm

JPWC wrote:I have two EXP-2's, both work fine, but they are not smooth high quality pedals I's hope they'd be.

Sure, there are a lot of pedals with a better mechanical "feel" and build quality. That's right.

I see a lot of Korg stuff in your signature - can you confirm that the EXP-2 work the same way on all the Korg products?

Sound like the OP needs to return his pedal or just give up and use the roland D-beam as their CC device.

Maybe, yes... I see a point where you can like a pedal or not - it's like keybeds, not everyone likes everything. For a matter of taste, OK.

But I think as long as you didn't get a cheap copy or (maybe?) a batch of the korg pedals is misfitted somehow, there is no "poor implementation" or "uneven response" in general.

Bruce Lychee · Post by **Bruce Lychee** » Sat Dec 08, 2012 6:45 pm

I have a few modified Ernie Ball expression pedals by Toneczar and Thru-tone. I ordered them for my guitar setups but use one on my Jupiter. Both have adjustable tapers. Toneczar has crazy waiting lists, so I recommend taking a look at Thru-tone. I have the EX-ULT.

http://www.thru-tone.com/Ernie_Ball_Exp.html