Here's a link to a german site, i think you will understand the PDF even if the text is in german. http://www.sengpielaudio.com/Anschluss- ... ofonen.pdfIf your 421 were the "hi" version with the high output impedance then there would be a small transformer inside, which is not too complicated to take out btw. Here's another, just a picture:http://www.sengpielaudio.com/MD421HNoderHL.gifYou will find 421s with green/red or blue/red wires inside, as far as i have seen. On some the green wire is green-blue, to complicate things For good measure i throw in some more pictures https://www.tonstudio-forum.de/index.ph ... 21-01-gif/https://www.manualscenter.com/manuals/s ... Q9j-n5CQ4Mgreen (or blue) = hi = XLR pin 2red = lo = XLR pin3black = ground = XLR pin1