On the back panel of the Altec 1566a, there is no plug in for an XLR jack. You must wire the mic by hooking up individual wires to various screws. You can change the ohms of the mic, depending on where you connect the mic wires. The options quoted from the manual are "high impedance microphone", "120/200 ohm microphone", and "30/50 ohm microphone".
My main use for this would be Royer R121 and Beyer M500 ribbon mics, but I would like to try it on other mics as well.
What I want to know is where people are hooking them up (which input) and what results they are getting. Also what kind of mics are you using and do you like the sound?