VC panner missing high end

[Troubleshooter]

Hi all,

I just built the first section of the VC-panner-mixer, the panning cirquit but the sound is very Lo-fi. All air (12-15Kz) content seems to disappear. Probing on the cirquit it seems the good sound disappears in the LM1700.

Any suggestions?

[Hubaswift]

Where did you source your LM13700s? I've often encountered fakes. If you bought from aliexpress, ebay, or some other cheap Chinese source I'd suspect them. Other than that I'm not sure I can be of too much help. The Yusynth output mixer is one of the few Yusynth modules I havenot built, and I still don't understand transconductance amplifiers (LM13700) as well as I'd like.

[Troubleshooter]

I solved the problem, taking out (bypassing) the output buffer transistors on pins 7,8,9,10 made the whole thing go from lo-fi to hi-fi. In many other designs peope leave them out for the same reason I figured out. A few other modifications needed to be made offcourse... I don't fully understand them either.

[Hubaswift]

Glad you got it sorted
Do you have a link to the post about modifications you mention? Might be handy for anyone reading or myself if I decide to build this module.

[Troubleshooter]

No there is no link. The mods are in my my head. I actually didnt build the whole yusynth mixer. I designed a mixer for an oberheim 4voice clone I am working on and used the the panning part of the yusynth to pan my voices in quadrature lfo mode. I changed a lot for inplementing it in my own mixer. It comes down to replacing the transistor buffers to opamp buffers and changing impedances for best sonic results. finding the sweetspot between signal to noise levels and distortion levels is challenging when using lm13700s.

[Hubaswift]