I have two Sennheiser MD 421-HN Microphones, and have been trying to figure out the correct wiring now for a while. They are currently wired unbalanced with a Tuchel to 1/4" cable which works, but the grounding is incorrect. I want to use the correct Tuchel to XLR configuration, but have not been successful at all. I've looked on forums everywhere and this is what I see posted:

Pin 1 is + 1500 Ohms
Pin 3 is + 200 Ohms
Pin 2 is -/common (for both impedance)
Connector casing/body is ground/shield

I tried this configuration and it doesn't work. (Note- I used Pin 3 @200 ohms instead of Pin 1@ 1500 ohms). There is a ground problem. You can hear it even without the Mic hooked up to the cable. When the mic is hooked up, it works and sounds good but don't touch the screen or you'll get a small shock.

There is no way this could be correct because a normal mixing board is expecting a ground from the one of the XLR pins. If the ground is only on the casing, how can a normal mixing board get the ground from the pin? Maybe these mics were used with some special German mixers or something, or maybe I'm missing something. PLEASE HELP!!!! THANKS

*Also, if anyone knows whether this is an unbalanced or balanced mic, please let me know. About 5 sources say unbalanced and about 3 sources are saying it can be wired balanced. Was it meant to be balanced or unbalanced??? Extremely confused....

randyj wrote:Pin 1 is + 1500 Ohms
Pin 3 is + 200 Ohms
Pin 2 is -/common (for both impedance)
Connector casing/body is ground/shield

Correct. Make sure you are referring to the pin numbers of the correct connector - ie. Tuchel or XLR. They have different pin-outs.

Works for me (and many others). Sounds like you have wired it wrongly or have an issue elsewhere.

There is no way this could be correct because a normal mixing board is expecting a ground from the one of the XLR pins.

The ground pin on a mic is connected to the body/grill. That's the whole point of it being there - to keep the body at ground potential. Using the body / tuchel barrel is a fine way to connect the earth.

*Also, if anyone knows whether this is an unbalanced or balanced mic, please let me know. About 5 sources say unbalanced and about 3 sources are saying it can be wired balanced. Was it meant to be balanced or unbalanced??? Extremely confused....

It's balanced. They wanted to give it two available output impedances balanced, but only had three pins - so, they decided you could use the metal barrel on the connector for earth instead which is fine despite annoying to solder.

Thanks for your reply, this must be where I'm getting it wrong. I assumed that the pin configuration below is for the Tuchel connector. Maybe this is for the XLR side, or is it for both? I know that 1 and 3 are normally reversed for the Tuchel, but would that apply to this situation since the ground is being connected to the case?

Pin 1 is + 1500 Ohms
Pin 3 is + 200 Ohms
Pin 2 is -/common (for both impedance)
Connector casing/body is ground/shield

XLR pin2 goes to Tuchel Pin3

XLR pin3 goes to Tuchel Pin2

Solder the shield at the Tuchel end to the housing barrel. Solder the shield at the XLR end to pin1.

O.K., I can figure that out, I'll be testing it shortly, thanks a million!

Finally, I got these Mics working right!!! They sound sweet!!! Thanks!!!!