Cathy75

Thanks. Yes, the one called "OUTPUT L/MONO". Can it be different? Yes. I have checked it with an electric device for that purpose. It shows all OK. The noise is not permanent. It is only noisy when dynamics escalates. I put all on a very low volume in order to test. If I increase volume on Theremin it gets very noisy. Now I have checked. I connected ONLY theremin into Behringer and it works without problem. I still suspect that I have one cable that is not good. I might try buying a good one. Is it just called "guitar/line cable 1/4 shielded"?

Many thanks that is indeed very very helpful. I still cannot figure what the problem is. 1. My theremin needs grounding. There is a grounding outlet and I have checked that the grounding is implemented. 2. Theremin is connected to Line6 Helix FX, to INPUT/L. 3. Line6 Helix is connected from OUTPUT/L to the Behringer UPHORIA UMC204HD - line input. 4. Behringer is USB powered via computer. 5. From Behringer I let line go through (not via computer) directly to the outputs. Output is balanced. 6. I use KRK Rokit4 speaker that is powered. I connected it to Behringer via balanced input on the speakers. There is no noise otherwise when I use the speaker (for playing music from the computer). That is completely true. * An additional question: Since I plan to give a setup to a another performer that will play this piece I compose, he will use a normal guitar amplifier. Theremin -> Line6 -> Amplifier So I guess I will need only these (two pieces) for the setup. Many thanks!

Actually I connected it now with cables I have, some are "speaker" cables, another are "guitar" cables, I try to figure out which are working. I am not sure which one is the correct. I use a very low volume to test it, but I get "buzz" all the time.

Thank you. The sound card is Behringer UPHORIA UMC204HD: https://www.thomann.de/gb/behringer_u_phoria_umc204hd.htm This is how it looks at the front, I have possibility to switch LINE/INST /PAD:

Hello friends! I have just got Line 6 HX and want to play with my theremin. It is Moog Theremin: https://www.thomann.de/gb/moog_etherwave_theremin_plus.htm Now, I want to connect the theremin to Line 6 HX, and than Line 6 HX to my sound card, thereafter to the speakers. What CABLES do I need: audio (for speakers) or instrument (such as electric violin, guitar)? I don't want to destroy my electronics... Thanks. s.m.