MC6 Pro + Lehle expression pedals

This worked just fine on my older MC8, but after upgrading to the MC6 Pro, the same expression pedals don’t behave correctly. I can sometimes get them to a stable 0% or 100%, but all values in between it flickers between neighbouring values.

It also doesn’t give stable numbers in the calibration process. See gifs below. Using the 10k output.

This is with the heel fully down, not moving:
ezgif-20f4eb60b07cb

And this is with the pedal somewhere in between:
ezgif-2065c4bc1a574

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Turns out this is interefence from my Walrus Canvas Power, no issue here for you.

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Just to clarify (for other users experiencing this issue), changing the power supply resolved the problem for you? How did you find out it is an issue from the Canas Power?

I went through some troubleshooting steps:

I have two Lehle Dual Expression units, one 3 years old and one brand new, and all tests returned the exact same results on both of them.

I have both the Canvas Power 15 and Canvas HP. I tried powering the Lehle with both of these and the output values reported by the MC6 Pro always flickered.

Then I tried disconnecting every other pedal from both PSUs, same issue. I also tried powering the MC6 Pro from another source to make sure it was not interefering in some way, same flickering issue.

Then I tried powering the Lehle with an external standalone 12v power brick (Lehle accepts 9-15v), and there was no issue.

I have previously used this exact same setup with a Fender Engine Room PSU, with no issue.

Therefore it is apparent that the issue is with the Walrus Audio PSUs. The one thing I should have tested but was not able to would have been to measure the resistance output of the Lehle and not relying on the MC6 Pro to report the values. I’ll try to do this too.

I’ve seen a few people on this forum talking about Lehle issues similar to this, I wonder if it is all a matter of the PSU they use. Lehle have a long standing reputation as market and quality leaders in their categories.

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Thanks for sharing. I’m assuming the Lehle is using a digital potentiometer so it seems like maybe some noise from the power supply is being leaked into the circuitry. Would be interesting to see on an oscillosope

Yeah the Lehle doesn’t have a mechanical pot, they use a hall effect sensor. I don’t see the interference on my ohm meter, I don’t have an oscilloscope.

James, as requested by Joki, a technician at Lehle, I tested the exact same setup with another digital device that shows me the readout. The issue does NOT happen there. This complicates the matter somewhat. This points to there being an issue between the MC6 Pro and the Walrus Audio PSU.

I am returning the Canvas PSU today and getting a Cioks tomorrow. Since they are the tried and tested PSU market leaders I’m assuming all will be fine with that but will report back.

I do think there is something here that Morningstar needs to look into.

I’m sure you could fix this with a firmware update, filtering out the noise values and averaging them out to stay steady at one value unless you get bigger movement. But I’m also quite sure the root cause is not on the Morningstar end.

ezgif-40c1d924b1181

You can try setting the expression sensitivity to LOW and see how it works for you in this case. Let me know?

When you tried with the MC6 PRO, both the Lehle and the MC6 PRO powered by the Walrus?
How about for when you tried with the H90?

I’m thinking more of a ground loop when are connected to the Walrus, causing noise since the Lehle is active circuitry. Have you tried MC6 PRO powered via USB power or a different power source from the Lehle?

Just wanted to chime in that I have the MC6 Pro with the Lehle Dual Expression and a Cioks DC7 powering everything and I’ve never seen this issue myself.

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James, I’ve had sensitivity set to low the whole time. The H90 and Lehle were both powered by the same Walrus during the test in the gif above. Also it’s hard to draw any concrete conclusions from the H90 + Lehle test because I don’t know if Eventide is doing some kind of averaging magic behind the scenes.

Note that I have two Lehle expression pedals, so I’ve been able to confirm all the below findings with both of them.

The only thing that fixes it 100% is powering the Lehle with something other than the Walrus. See below:

Bad flickering/unusable:
MC6 Pro and Lehle powered on the same Walrus
MC6 Pro and Lehle powered with different Walrus (I have two units)

Much better, only flickering while “settling” on the number when the pedal is stopped, then steady:
MC6 Pro on USB power - Lehle powered by Walrus

Rock solid:
MC6 on any power source including Walrus - Lehle on anything OTHER than Walrus

Since I’m no electromagician I don’t know much here, but would a ground loop point to some kind of improper isolation thing with the Walrus PSUs?

Also, check this out, I went to the calibration screen, since that’s where you get the highest resolution read-out. This was with the MC6 Pro powered via USB from my computer, not plugged in. The Lehle is in full heel-position the whole time.

Lehle powered by a random walwart style PSU, only jumps +/- 1:
ezgif-5bb74b9817443

Lehle powered by Walrus, much bigger jumps:
ezgif-5bdea51b6299b

Thanks for the input, that’s great to know because I’m shipping the Walrus PSUs back to Thomann tomorrow and will be using Cioks DC7 instead :slight_smile:

This does sound like the Walrus isn’t as isolated as it should be. For sure, Cioks are world class and isolated properly.

I recently got the mc6 pro and had an issue with expression calibration–using a boss ev5. When i moved the pedal it behaved the same way. It took me a while to realize that i had plugged the pedal into the expression 4 jack on the Morningstar, but the unit was displaying calibration info for exp 1 when i moved the pedal. Once i changed the settings to reflect that I was plugged into Jack 4 all the problems disappeared and the pedal worked correctly. I didn’t realize that could happen, and it was a simple mistake on my part, but figured I’d mention it.

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Had the same issue with my Lehle Dual expression and the MC8 (plus Cioks DC7).

Were you powering both with a DC7? Did it disappear if you powered either one with something else? Did you find a solution or did you ditch something from that equation?

Hmm. Other things probably worth trying, as daft as they might sound: try different TRS cables. Have you got other expression pedals you can test with? I wonder if the problem goes away with a really simple unit that definitely works jitter and noise free (this works, is cheap and can be returned via Prime after testing! M-Audio EX-P - Expression Pedal for Keyboards, MIDI Keyboards / Controllers and Supported Guitar Effects Pedals, Black: Amazon.co.uk: Musical Instruments & DJ)

That pedal would most probably not have the issue since it’s fully analog. The issue has nothing to with the TRS cable, the only thing that fixed it was powering the expression pedal with something else than the Walrus PSU.

yeah, got rid of the expression pedal… :confused:

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That’s a shame, I really don’t want to go back to an expression pedal with a mechanical pot that gets dirty and wears out…