CV Tune Issue: Pyramid - Roland MC-202?


#1

I’ve got a curious issue.

I’ve been using and enjoying the CV inputs and outputs on the Pyramid for years now. Squarp guided me through the modification required to remove a few of the SMD components and correct a problem with the CV outputs from the first generation of Pyramids, and so far I haven’t had any trouble. Love my Pyramid so very much.

Recently I restored an MC-202 and thought I might like to use it live in place of the Roland Boutique SH-01A.
The CV inputs are quantized, so they sound really bad. To correct this I added a modification which provides proper CV and Gate input. The modifications went well, and the device is beautifully restored and functional. Great story, right?

Well… for reasons which I can’t understand the tuning of the MC-202 is correct internally, it is correct using the Arturia Keystep’s Pitch and Gate outputs, it is correct using the Roland CSQ-600 as the sequencer, but when I connect the Pyramid is goes completely wrong.

At middle C is G3 plays the C3 note.
At C1 - it ls just a little flat.
By C5 were are on the moon.

The calibration tools provided within the Pyramid to adjust for CV mis-calibration don’t correct the problem. I can use them to tune the C3 to be a C3 - a few coarse steps, and then some fine % until it’s right, but by the time we play away a few notes it begins to come out of tune again.

Normally I would open the MC-202 and recalibrate it - set the spread correctly, and internally tune it to the proper voltage and then assume that the problem was the MC-202. Makes sense.

But this problem is only with the Pyramid. Everything else plays nearly 5 octaves in tune.
Further, the internal CV voltages (not using my modification inputs) do play correctly, but you can hear the CPU quantizing, and attempting to adjust the incorrect voltages from the Pyramid to the correct notes of the CPU. It becomes totally Vocalign, and unusable.

What the heck is going on?

The interesting thing is that using the same Pyramid, same cables and same pitches with an SH-101 there is no problem at all. It’s just fine. With Eurorack gear it’s also fine. No problem.

This is the first CV/Gate device which has not been what I would call “compatible” with the Pyramid since being guided through the correction to adjust the CV/Gate outputs and inputs years ago.

Nuts.

I’d love any input or thoughts you might have. Has anyone else encountered anything like this?


#2

Dumb guess: maybe CV OUT TYPE is set to the wrong value in CV/Pedal settings.


#3

Right. Yes that was the first thing I investigated.

1V/Oct and all is set correctly.

HERE IS THE WIERD PART
The same settings work just fine with an SH-101 (effectively the same device)
And what’s weirder is that using the Arturia Keystep to sequence the MC-202 it works fine too.
It’s only the Pyramid CV/Gate outs that are weird with the 202 (nothing else.)

Baffled.


#4

Well, it seems like for one reason or another, the CV droops in the MC-202 and it doesn’t in the SH-101, or between the Pyramid and other devices.

I’ll try putting a buffered multi between the Pyramid’s output and the MC-202’s input and see if this corrected the droop. If it does it seems that I’ll need to concoct some way of buffering the input for the 202, rather than adjusting the Pyramid.


#5

I’d try an active buffered multi before i do any recalibration again, what you describe could be because of that. Is the 101 input circuitry different from the 202?


#6

Tricky to diagnose, but it would seem to be an issue with the new 202 CV inputs impedance.

I’d suggest measuring the CV out on the Pyramid with a voltmeter, say middle C, the octave below, and the octave above, then measure the same notes on the Keystep CV outputs, obviously a 1v difference between the readings would just mean that the voltage assignments for a given note between Pyramid and the Keystep are different, but if it is the same otherwise (that is to say within less than about 0.03v deviation) then it is almost certainly an impedance mismatch.

You could try adding an inline resistor between the CV socket and the wire inside the 202, try between 100ohms - 1k and it might provide enough resistance to negate the need of a buffer.

Just a theory, but that is what I’d try.


#7

curious…Having same unique issue with a 202 and Hermod (strange pitch droop)… 202 is modded w/ Kenton cv/gate kit and pitch is perfect with Eloquencer.


#8

I’ve resolved the problem by using the CV.OCD as the midi/CV interface for the MC-202.
I dont regret modifying the 202 with proper CV/Gate inputs, and have been looking into how to include buffers to prevent the droop, there IS a buffer on the pre CPU CV/Gate inputs stock, so it’s possible to make this work, however, there isn’t much room inside the small space (even flipping the components from just on the other side of the mock 3.5mm jack spaces from the top of the board to the bottom.)

I don’t know why it works without droop using the CV.ODC or other sequencers and not with the Pyramid.


#9

I have the same issue : MC202 internal tracking is fine, but trying to use it with the Pyramid output doesn’t track properly.
The Pyramid can sequence other external gear fine.
The MC202 features a mod allowing for proper cv/gate inputs.


#10

The MC-202 has a CPU which quantizes external CV input and makes it sound terrible.
So this means that the external CV/Gate inputs can only handle really basic patterns, I have gotten it to work, but I’ve never been really happy with it.

I performed the “proper CV and Gate” mod on my MC-202
I chose to flip the components behind the unused jack indentations on the back of the MC-202 to the bottom of the PCB to make room for two more jacks and added the “proper CV/Gate” mod there.
This is un quantized, and it sounds fantastic.

Here are a couple of links to the mod:
One form Din Sync

And one from Subatomic
https://www.subatomicglue.com/202l0g/SubatomicMc202Mods.html