VCO frequency increases when plugging in Midibox CV

[LetterBeacon]

I've just finish building a Midibox CV to control my modular and I'm having a slight problem with the pitch of my DIY VCO when I plug the Midibox CV out into the CV in.

When I plug the Midibox CV Out > VCO CV In, the pitch of my VCO increases by a few octaves, despite there being no voltage present out of the Midibox CV. Is this normal?

Should there be a difference in pitch from when the VCO is free running (i.e. with nothing plugged into its CV in) to when there is a cable plugged into the CV in but with 0.00V present?

I've checked with a multimeter and there is no potential difference between the ground of my VCO and the ground of the Midibox.

Should I just recalibrate my DIY VCO trimpots so it's lowest frequency is C0 when the Midibox is plugged in?

[Sebo]

Hi:
I have a MIDIbox CV, and when I patch it to my Yusynth VCO the pitch of them
goes up, I'm not shure how much, but is not a problem.
I calibrated the initial frequency of the VCOs with the 1V/Oct input tied to ground
(as Yves stated in the calibrating procedure). When I plug the MCV and hit
the bottom C note
(0V) I got the same frequency I get in the calibration.
I think that MIDIbox CV is outputing some voltage when is turned on.

[LetterBeacon]

Thanks for that Sebo. I'm pretty sure I tied my VCO to ground when I calibrated but maybe not!

I might try calibrating the initial frequency again and tie the 1V/Oct to the output of my MBCV when it's outputting 0v.

Thanks!