FLXS1 CV out calibration?


Yikes that doesn’t seem good! How do your outputs track in Volts across octaves?


Now I’m even more confused. I’m comparing the flxs and the varigate. They are both putting out the same voltage and both are correct according to data???

I’m completely baffled. How does two sequencers putting out the same voltage affect the same osc in different ways???


You could be experiencing some impedance related variations.

Every device connected to FLXS1 draws a tiny bit of current from the outputs. The higher the input impedance of the device that you are sequencing, the less current they draw.

FLXS1 is well suited to oscillators and sound modules that have an input impedance of 100k or higher. Some modules have lower input impedances than that, which will result in a slight dip in voltage when they are connected, which will result in a slight dip in pitch. The more modules you connect to a single output, the more current they draw, and the bigger the voltage drop. If you connect through a voltage buffer, that buffer usually has a very high impedance, and will buffer the voltage so whatever you have connected to the chain after that will have current drawn based on the output impedance of that voltage buffer.

FLXS1 has 1k output resistors, which I modeled off of Mutable Yarns. In hindsight, I would have lowered this value to 500, or maybe even 250, but 1k generally works well for most situations. It is really apparent when you use FLXS1 with modules that have a very low input impedance (50k or less)

ALSO - very important. Make sure you are doing all your measurements and calibration after a good thorough warm up. Cold electronics do not behave the same way as warm ones do, so a good rule of thumb is to wait 10 minutes after you boot your machines to do any measurements or calibration. I learned this the hard way when had to recalibrate 50 FLXS1s during my initial kickstarter run after I did them all cold, and when double checking realized they were all off when they warmed up.


yes, i think its to do with the output resistors on the flxs1 .i was getting similar issue to ndoemusic above ,the correct voltage from flxs1 in to the mordax data and then “wrong” voltage in to a vco but if you put an attenuator or mixer between the flxs1 and the vco it works fine (after calibration )

thanks for all the input


My outputs are still running about 0.2v to 0.5v out after calibration. I started using my fluke multimeter for better readings. Any details to manually trim these?


Im not sure what to do here. I don’t have a single sound source that is tracking well with the flxs. I have tested the CsL, Akemie castle, ER-301, Plaits. I cant get any of them to track good enough. If i use my marbles,varigate or voltage block i can get better tracking, almost perfect.

I don’t want to use other modules to correct this issue as it is not what i intended. Also my tracking issue run each way +/- so if i correct with an attenuator it will not trim or scale it correctly only offset it. So id have to get something to scale each output to a specific sound source then if i wanted to change OSC id have to do it all over again. I know it can work but this shouldn’t be what i have to do to get it to work.

OK i had my rack on for at least 2 hours before i did any tests or calibration.

So Id like to know a good fix for this and would also like to know how to manually trim the outputs as well.


It is possible that there is something wrong with your module specifically, but I would not be able to know unless I took a look at it.

There are a few options here:

  1. Use a buffer - as you said, not ideal because you have to add gear.

  2. In the calibraiton menu, on the second page, it shows CV1a, CV1b etc etc. Those values represent the lowest, and the highest values sent to the dac, which represent -10v and +10v. You can adjust those manually to see if you can get a perfect tuning. That would be a very difficult thing to do for each individual module

  3. Send it in to me for evaluation. I can also replace the output resistors, which may help to a certain degree.

  4. Replace the output resistors yourself. This is a very advanced option which requires significant SMD experience. I am not going to post exactly what to do here, but if anyone wishes to modify their FLXS1, they may do so at their own risk. It would involve disassembling FLXS1, de-soldering 8 SMD 0603 components, and replacing them, and then testing.

Of course, FLXS1 should track for you, and it should track well, since it is a pitch sequencer. Its kind of an important job…

Justin, you can send me an email (you have my address) if you want to send it in. I just ask that you cover shipping expenses.


Since i experience the same i tried checking which serialnumber my flxs1 had, but noticed that the grey area on the bottom left is blank. no serial code is written.
i bought it secondhand from modulargrid from a user named vytis who is still selling flxs1’s after i bought one from him so was wondering also what that was all about.


I sent you an email.


What are you guys using to calibrate the FLXS one with?


It has an internal one but the code needs to be rewritten. I think it is in his list of stuff to do after super booth. But I can’t be certain of that


Hi, I think issue is related so if not I can start a new thread. I tuned by Spectrum Osc with o_C reference app to C0. Yet, when I fire up my FLXS1 I have to set pitches to C3 or else its 2 octaves under. Am I missing something here? Why is C0 on the FLXS1 more like C-2?


There is a way to set the output range for each track somewhere in the global menu.


Thanks, I set it to -2 to 8 range and that seems to work better.