Open Theremin v3 Audio

Good morning from sunny SC USA! 

I recently built the OT v3 and have a question about the audio jack. 

What is the best method of connecting my OT to my Yamaha MG10XU mixer?

I’ve tried a normal male to male 3.5mm stereo cable to a y-cable with 2 1/8 males in to my mixer. Sound only is broadcasting from one channel. Is this correct? 

I’m hoping to create some interesting sounds with the built in FX features of the mixer. 

Thanks for all of the help. 

Yeah, it's a stereo jack, but a mono out. I use a TRS 3.5 to TRS 1/4 cable to a single mixer input.

I have some stereo panning eurorack modules that I use to get a stereo image...in conjunction with an LFO or other CV device.