VCO tuning and scaling issues

I tried playing my 400 VCO from Elektron A4 and noticed that the scaling is way off, can barely get 1 octave in tune on any of the VCOs.

Has anyone had any luck getting theirs to play in tune? I allowed it to warm up for 30 minutes after the first unsuccessful attempt, and obviously I was using a correctly rated power supply.

I know the VCO’s have trimmers on them but I’m reluctant to take it all apart if they are not going to solve the issue, also they are very small smt trimmers so pretty difficult to adjust.

Is there no calibration procedure ?

No, just a separate sheet which shows the trimmer labelled tune, no details in main manual.

To be honest it isn’t a deal breaker for me personally, as I have plenty of other oscillators that track well, but I think it will be a problem for some people, so I hope TE sort it.

BTW - Elektronauts down? @LyingDalai

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Mine appears to track about 2.5 - 3 octaves well - then it starts to get a bit wonky tuning wise. I haven’t touched the trimmers assuming it was set up correctly at TE.

Ide email their support to determine the procedure for the trimmers - but be prepared to wait a few days for an answer.

Have you also checked the A4 CV offset for tuning? - I’ve found mine all messed up before which prevented modules from tracking properly.

EDIT: I’ve noticed that upon firing up the unit, the tracking is pretty bad - understandably being an analog synth. After a few minutes of warmup, I find the tracking to be much smoother/steady across about 3 octaves.

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The saw wave has a second frequency running though it. Making it almost impossible to get one straight note out. The square and sine seem to track better because they are more stable. I was using an Agilent Technologies O-Scope and I did upgrade the power supply. But now that it stays on I can scope it and say that try playing with square and sine for things you want in tune, and the saw for more percussive or stuff you don’t mind about the tuning. That may help.

Time for a tune up with a trimmer?

its a bit more complicated.

There is a second frequency somehow running through the saw. I don’t believe it was intentional.
There is no way to get rid of it. My guess is a cap would do the trick somewhere on the board to
even out power supply ripple. But I’m not a for real EE so thats a guess.

Its like you always have something Sync FMing the Saw Oscillator.

Could be some kind of balance thing with internal trimmers, but i do not have the system 400.

The two trimmers are the center tuning frequency and Volt Per Octave.
There is not a third trimmer and it is a single oscillator. If it were a complex
oscillator like a Buchla 259 or Hertz Donut then I could see why there is
a second frequency floating in an oscillator path, but on a single oscillator
there should only be one frequency.

Maybe it is saw width modulation :slight_smile:

it sounds really cool and its not that bad its just not 100% stable with the saw.
This little modular has a lot of character. definitely a nice DIY project.
the square and sine seem to be pretty in tune over three octaves. Its
what I would expect from a small simple modular. Wish there were faceplates and
a way to get them out of this yellow thing and into a case. the back of the manual
has some info that says some type of chassis, but I dunno?

And after a while it doesn’t stabilize? Cause the osc are not heat regulated probably.
Well it can be a thousand things. Maybe a pot that is not well aligned. It sounds like something simple.
Good luck finding it.