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CV out calibration

CV out calibration
« on: July 12, 2020, 09:37:27 AM »
Anyone have tips for calibrating the CV outs for eurorack 1v/oct? 
Iím using a mod slot with note number as the source and CV1 out as the destination with amount at full.  I canít get a full octave in tune.  Tried playing with DC offset and scale in the global section but after an hour I gave up.

W07

Re: CV out calibration
« Reply #1 on: July 18, 2020, 06:22:52 AM »
1.Set note number as source, CV out as destination at maximum amount.
2. Connect to V/oct input of your oscillator, play a low note, about the lowest note you'd want to play, (but once tracked it will give a nearly perfect octave below as well)
3. use a tuner to tune the oscillator to this low note.
4. Go up an octave, see how much the tuning of the oscillator is off, probably it'll be lower.
5. Go to CV scale, and increase the amount until the osc hits the exact octave higher note. If you go up another octave, you'll probaly need to adjust a bit more. Go back and forth or up and down the the octaves till all of them get hit as close as possible. Don't forget to go back to the original low note to see if it still tuned dead on, if not you can use the cv out offset to compensate.

I usually end up with 4 to 5 octaves that track decently, depending on the oscillator. usually my cv scale offset is somewhere between 24 and 32. If it is a lot more off, the oscillator might need calibration itself.

not all oscillators will respond equally, so if another osc is detuned a lot, you might want to use a different CV out and repeat this process.

Some soundsources, like loquelic iteritas use a higher voltage as C1, so in this case you might want to set CV out offset to +64 first, and then do the calibration as described above.
« Last Edit: July 18, 2020, 06:28:06 AM by W07 »

chysn

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Re: CV out calibration
« Reply #2 on: June 11, 2021, 05:29:07 AM »
W07's procedure is good, and will get you in the ballpark. But both an electronic tuner and an oscillator will introduce inaccuracies. Using a decent multimeter will improve your CV calibration.

Use your multimeter to find the voltage of the lowest C of transpose setting 0, which should be close to 0V. Adjust the offset value a little until you get exactly 0.00V.

Now play two octaves up. You're probably close to 2V here, but go to the corresponding output scale value and adjust that until you're at 2.00V. After this step, you'll be really close, maybe as close as you need.

But the scale adjustment will have affected your 0.00V key, so go back and see how close 0.00V is again, and adjust the offset again, if necessary. Once you get 0V and 2V nailed down, proceed up to 3.00V (highest C at 0 transpose).

You'll need to leave Global to choose another transpose setting, but check the -1 setting, and check for negative voltages at various Cs (-1.00V, -2.00V).

On my Pro 3, I had nearly perfect calibration from -4V to 4V after only two passes, but it may require more.

Note that all four of your CV outputs will have different values, so if you want to use them all, you'll have to calibrate them all independently.

Consider writing down your scale and offset settings, in case your Pro 3 gets wiped for some reason.
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Re: CV out calibration
« Reply #3 on: June 13, 2021, 04:38:40 PM »
Just more insight into this matter.

I noticed all DC coupled interfaces have some DC offsets, my Pro 3, Expert Sleepers ES-8 etc.

Seems inherently unavoidable hardware issue ...

ES-8 have a plugin in VCV Rack called Silent Way to do soft-calibrations. Meanwhile, there isn't anything similar for Pro 3 ...

Otherwise, just tune your oscillator or use a MIDI to CV interface for v/oct
« Last Edit: June 13, 2021, 04:48:05 PM by Wavtekt »