Hi Stefan, Thanks for helping me out ! I followed your advices, but the problem was still not solved. I then decided to troubleshoot the module, by following the traces and injecting audio and modulation signals into channel 2. I discovered that the modulation input on PIN 3 of OTA 4 was not receiving any PAN modulation signal, which led me to identify LED8 as the source of the problem : it appears that the PAN LEDs are in series with the modulation signals, which is not obvious at all! Probably due to the fact that the OTAs use current and not voltage for the signals. I replaced the LED, and problem was solved, et voilà ! A dead LED is a first for me! Looking forward bulding other modules : already bought Shikensa, Clipping cat, Push, Matrico and Dirty Dan. Thanks again for providing us with these great modules, I whish you the best. Christian.