CM-311A, CM-311AE, CM-312AE and Sennheiser Evolution transmitter
Will the Crown CM-311AE or CM-312AE work with a Sennheiser Evolution transmitter?
Reply: The Crown CM-311A microphone (with the belt pack) will work if you connect its XLR output to the Sennheiser transmitter. XLR pin 2 = mic signal, XLR pins 1 and 3 = shield or ground. Put a 4.7 uF capacitor in-line with pin 2 to block DC from the transmitter, with the + side of the capacitor toward the transmitter.
The Crown CM-311AE or CM-312AE headworn mic works with Sennheiser's new Evolution G2 transmitter. You'll need to solder a 3.5mm (mini) stereo phone plug to the end of the mic cable, ideally using a locking phone plug from Sennheiser. Solder the mic-cable red lead to tip, white to ring, and shield to sleeve.
Use the transmitter's menu to change the sensitivity from 30 dB to 0 dB. The mic will work dependable for at least 10 hours without changing batteries. The mic might start distorting as battery power drops, and a fresh set of batteries should fix the problem.
The transmitter's battery life can be extended if you modify the transmitter’s electronics. Sennheiser supplied a diagram that shows how to do it.
To see wiring instructions for other transmitters, go to this link: Technical Bulletin #3
If the signal level is too low, Sennheiser has suggested wiring the white and red leads to the phone-plug tip. However, the EQ circuit that is inline with the cable does not work with that wiring. To get a higher output signal, you could cut off the EQ circuit, then solder the white and red leads to tip. Then the bass will be very weak. You will need to turn up the bass (low frequencies) on your mixer EQ to compensate. That might be an acceptable solution.