If memory serves, those looked like a cross between a mini Sennheiser 421 - and an electric razor.. LOL...
I remember hearing at one time that Norelco made the body for them - although that might have just been a myth based on their appearance and similarity to an electric shaver.

Beyond that, I don't know much more about them; other than that Beyer has always had a solid reputation for making great mics..

Niels Münster, post: 443386, member: 50080 wrote: Could the problem be in the tuchel-XLR adapters

That's where I would look first. You may want to contact Beyer and make sure that the Klein-Tuchel adapter will work on that model; because even if the adapter physically fits the socket, that doesn't necessarily mean that it will work for this particular model; if the pin-out wiring is different between the mic, the jack on the mic end, and the jack on the preamp end.

Niels Münster, post: 443386, member: 50080 wrote: Or did I simply buy a pair of lemons

Well, yeah, I suppose it's possible, if you bought them from someone who had perhaps attempted to mod them in any way, or perhaps to fix a faulty connection or something, without really knowing what they were doing... it wouldn't be the first time;
But the fact that both mics suffer from the same problem(s) points ( to me IMO) in the direction of the KT cable you are using.

Besides that, have you looked at the connections on the KT/XLR jack ( on both ends) to make sure there aren't any faulty solder joints?
You mentioned buzz/hum/noise... which is it? Because there is a difference - diagnostically speaking - and the type of noise can often be a good indicator of the source of the issue(s).

Generally, "buzz" will indicate a grounding issue ( but not always)... "hum' and "noise" can indicate a bad cable, or one improperly wired.

I'm also assuming that the "GAP-73" you mentioned is a Golden Age Neve-style 1073 mic pre? That pre should have plenty of gain...

I'd start with contacting Beyer and asking them about the Tuchel. They may have a list of their older mics which will - and won't - work with that type of adaptive cable...

http://europe.beyerdynamic.com/contact.html

beyond what I've mentioned, I'd hand the ball off on this one to Boswell ( Boswell )
or Dave ( dvdhawk ); these two guys are far more savvy with electronics and repair than I am. ;)

-donny

Hi Donny,

Thank you so much for your more than merely fulfilling response. I have written to Beyer now and will await response - and post the result here.

Best regards,
Niels

I've never used an M81, but I do know that the wiring on their Klein Tuchel connector is not the standard as used on the M69, so it's unlikely that any of the readily-available Tuchel-XLRs adaptors will work. If you manage to get the pinout information from Beyer, we can suggest how you could re-wire your existing adaptor.

I'm pretty certain there were 3 versions of these - Hi impedance, unbalanced, medium impedence (250-600) balanced and a balanced low impedance one which I think was 25-50 Ohm. The Shure 545 which was similar period had the medium and high impedance selection, and in the 70s, when people dug these up, they often had all sorts of noise and tone issues when using them in the wrong mode. From your description I bet they're high impedance versions - plug them into a guitar amp and see if they produce hum free output.