Old Sennheiser MD 421, version/wires...? With pictures

[mysterio]

Hi!

I have an old Sennheiser MD 421 microphone and I could use some help. My goal is to understand this microphone so I can get an adapter cable and end up with a fully functioning mic.

Basically, all I know about it is it's an old MD 421. The Little Plate with the model name is missing, but it has the "klein tuchel" connector so I am assuming that it's either the "N" version or the "HL"/"HN" version with the varying impedance.

So, in order to find out what I have I started taking it apart. When I took out the connector part to look at the round metal thing for a model number there it seems to only say "MD 421." but it's a little bit hard to make out.

When I looked at the wiring inside the microphone there seems to be only two wires soldered to the connector part, one red and one blue. This makes me a bit suspicious. I don't know that much about electronics and microphones really, but I thought that these were supposed to be balanced microphones, so shouldn't there be three wires and not two? One hot, one cold, and one ground?

So basically I have two questions:

1) Can anyone tell if this is the "N" or "HN"/"HL" version of the microphone?

2) Is there something wrong with the wiring inside the microphone, like it missing a ground wire? Based on what I've read I would have expected it to have a black wire for ground in addition to the red and blue ones.

I tried attaching some pictures of the microphone that I hope can be helpful.

Appreciate any help

[Drew Stephenson]

Picture links aren't working for me I'm afraid.

[Hugh Robjohns]

... it has the "klein tuchel" connector so I am assuming that it's either the "N" version or the "HL"/"HN" version with the varying impedance. ... inside the microphone there seems to be only two wires soldered to the connector part, one red and one blue.

Sounds like it's the N version to me. The switchable impedance version uses a transformer and that would probably mean three wires down to the connector instead of just two direct from the capsule.

... But having said that, I'm no expert on MD421s! There is a 'service manual' here: https://www.manualscenter.com/manuals/sennheiser/md421-service-manual.html#.XQYuNFVKjRY And that shows two wires coming from the filter block to the connector. So it seems the wiring is normal.

I thought that these were supposed to be balanced microphones, so shouldn't there be three wires and not two? One hot, one cold, and one ground?

The ground you mention is only for an electrostatic shield or screen; it plays no part at all in transferring the signal. So there will only be two wires coming from the moving-coil
capsule which generates a 'floating' (ie not referenced to ground) balanced output. Those two wires will go to pins 1 and 3 on the Tuchel connector. Pin 2 is the ground pin and that will be bonded directly to the mic's metal case some how to provide the (Faraday) screening.

[Janneman]

Ask Sennheiser. They are very helpfull.

[mysterio]

Oops, seems I screwed up with the pictures!

Hope it works now:







Hugh, thanks for the great post. What you're saying seems to make sense. As I'm a bit of newbie to this I still don't exactly understand how it all works, but I'm learning lots!

[Mike Stranks]

... and should you need them there are numerous Tuchel-XLR adapters available on EBay...

[DGL.]

And sennheiser do a replacement XLR connector that solders in place of the Tuchel connector https://www.thomann.de/gb/sennheiser_um ... md_441.htm