You’re saying you’re adjusting clockwise and then counterclockwise and you’re back to where you started. Well of course you are.
See if the two pitches are more than or less than two octaves apart. Turn the trimmer one way and check both pitches again, see if they’re closer to two octaves apart than they were or further. If they’re further then you need to turn the trimmer the other way. Now that you know which way it should turn, keep turning it that way and checking both pitches. They should get closer and closer to two octaves apart.
If the spacing between the notes doesn’t change when you change the trimmer position in a single direction, no matter how much you turn it, then something is wrong, but I doubt that.
So the frequency ratio is 3.95, less than two octaves.
Now the frequency ratio is 3.93. It’s further from two octaves. The fact that C4 is in tune and C6 is flat isn’t relevant. Don’t pay attention to the pitch, only the pitch difference.
You got further from two octaves, so turn clockwise. It’ll get back to 264 and 1046 (3.95 ratio). At this point C6 is in tune again but that’s not important. Keep turning it further clockwise. Both frequencies now will be out of tune but the ratio will get closer to 4.00. When it reaches 4.00 you stop. And now you put both in tune by adjusting the center frequency trimmer.
Ok I made some progress but now the octave switch is off.
I adjusted the tracking trim pot to get the octave span correct. Then I adjusted the center frequency trimmer like you said, but now the octave switch is not calibrated (which was before).
I tried adjusting the octave switch with the instructions on the quick start guide using the “center” trimmer" but then it throws off the pitch tracking that I just calibrated.
In that case the reference voltage (the 4v) may be off or the pitch cv you are sending in isn’t accurate. In the former case, adjust the REF until the test point on the back reaches 4v. If the latter, you can still make it work by adjusting the reference to be more or less than 4v in accordance with how off your keyboard or sequencer is, but that’s definitely fiddly. Did you measure the voltage of the incoming signal ( the data is OK for this, but a digital multimeter with more digits is better). If the input CV is accurate, it must be the reference voltage that needs calibrating.
I’m sorry you’re having this issue, I know it’s not how you want to spend the time when you get a new module. We’ll get you there.
I checked the reference voltage and it was at 4.06. Adjusted it to 4.0
The issue persist. My keyboard tracks pitch correctly, but the octave switch is now off. As you go from the lowest setting to the highest, it gets progressively sharper.
Before I attempted calibration, the octave switch was the only thing “tracking” correctly. But now the reverse is true, pitch is correct but octave switch is incorrect.
I calibrated it again based on the video. I got the octave switch correct, but now the pitch is drastically out of tune again when using any CV 1/oct keyboard. Right back where I started. Do I have a faulty unit?
I was able to get pitch tracking to work, but then the octave switch doesn’t work.
I got the octave switch to work, but then the pitch tracking doesn’t work.
Reference voltage adjusted to 4 from 4.06, but that didn’t seem to help.
I did verify my pitch sources (Akai MPC, Arturia Keystep, and Eloquencer) and tested those with other modules and with the Mordax, and those are submitting correct pitch/CV up and down the key range.
One thing you might want to check is if the control voltage is accurate while it is plugged into the VCO. The VCO has a 100k input resistor and if the CV source has something like a 1k output resistor then a 1 V difference measured when not plugged in will become about a 0.99 V difference when it is. My Mother-32 behaves that way and I got around it by boosting the CV with an external amplifier (a buffered multiple with tunable gain). But since you mention multiple CV sources including the Keystep, and my Keystep evidently doesn’t have that 1k output resistor, that might not be the issue.
If the CV really is accurately 1 V/octave when plugged in, and the Vref really is accurately 4.00 V, and when you calibrate with one the other doesn’t track, then I’d suspect R19 and R22 aren’t well matched.
A workaround is to calibrate the VCO to work with the CV sources, and then tweak the Vref trimmer to make the octave switch produce octaves.
I sent you an email from your website since I can’t find the DM option here.
Let me know if you received it so I can reply back with the details requested.
@space, the issue was a bum voltage reference. Every so often, one of them will be near impossible to get to exactly 4v, I must have missed this one. I switched it out and no calibration issues.
For everyone else’s information, I just sent a fresh one as a replacement and got the other one back. Once I tried tweaking the reference voltage, the issue was pretty obvious.
I’m really glad to hear it! I thought I sucked at calibration or that I was going crazy. The replacement module is amazing and I just ordered the GRRR filter to go along with it. Thank you so much for helping me out! I’ll be getting a second VCO after the GRRR filter!
I like these knobs, my synth is completely covered in them (or the Tayda clones at least), but also i can never look at them without thinking they make it look a bit like the world’s most complicated stove.
Hi Christian,
Not sure where to post this but hopefully this is ok. I also got one of these (via thonk) and everything appears to be great, sounds great, the 4v ref is fine and I got it in tune across the the octaves using the switch, except I’m also having a tracking issue.
My one is that over the span of 6-7 notes it goes from C to outside the audio range, no matter where the tracking trim is set. I’ve looked at the incoming CV voltages and they’re normal (and other oscillators are fine with it)
I’m assuming I’ve done something crazy but I’m not sure where to look, do you have any thoughts on where to start looking for something like that?
To make sure we understand: Are you saying the octave switch works, changing the pitch by octaves as it should, but the control voltage input changes the pitch by way too much?
If so that sounds like the input resistor is too small a value. It’s supposed to be 100k. As I understand it the kit version comes with the SMD resistors already soldered, so if it’s wrong, it’s presumably a factory mistake.
Does it happen with both the V/Oct input and the CV input, or just one? If both then it seems like two resistors are wrong.
It should be possible to check this with a multimeter since there’s nothing in parallel with those resistors. If that’s what it is, fixing it would require unsoldering the resistors and soldering correct ones.
Hi,
Yup it was the DIY kit, with the SMD components already soldered
The octave switch works as expected and the CV one seems to as well, but yeah the control voltage input seems to be pretty odd
Is that resistor R22? I’ve not been able to find a schematic for the eurorack modules
The schematic is almost the exact same. To me this sounds more like an issue with the tracking trimmer. I find it unlikely that there would be an issue with the SMD resistor, but is there any chance you accidentally desoldered any of the SMD components? That happens to the best of us.
Morning (in NZ),
It’s definitely possible I’ve desoldered something, but I was just checking, the schematic says that R22 should be 100k, and my MM says it’s 10k (and is 01C), so do you think it’s worth having a go at switching that out?
I think I have some 100k SMDs around, otherwise I can maybe wrangle a through-hole on there somehow
That’s honestly horrifying. I only made one batch and looking at the boards I have left, R22 is 01D and measures 100K. I’m not sure how a 01C would get placed in the factory.
