[Scott Dorsey]

Peter Larsen wrote:
Scott Dorsey wrote:

Null on the BM5 isn't bad but the output is very low.

I built a booster-amp for it with a Hitachi MC-preamp chip, works fine with
unbalanced input except for a bit of buzz from the upper capsule. Some of
the time I'm a coward, so I have NOT felt any inclination to disassemble the
mic-pair and investigate.

I would first rewire the mike for balanced output. The transformers are
inherently balanced; the only reason the output is unbalanced is that one
end is tied to ground.

I might also try and replace them with Royer's new designs.

Could be that it is a better idea to build a trannybox, I have a pair of
Sennheiser TM005's that I used to use in reverse as input transformers in my
A77 with input board bypassed, ie. directly to the rec-level pots. I should
have thought of ripping the input transformers from the becords that I had
no room for keeping and not only ripped the heads, but the TM005 is probably
better as a step-up.

You need gain. Stepping up the voltage means stepping down the impedance
and that's not going to make the ribbon happy.

And that pristine BM5 which has just about done nothing - I did use it to
record a voice improvisation in 1985, great sound on vox if not close, great
space just recording in a reasonable listening-room - but sleep in its fine
wooden box for 50 years? - should I not worry or stand the box on its end in
the mic drawer? - mind you, its precious, I paid DKK 250 for it and it is
one of the products Bang & Olufsen seemingly do not want to be reminded of
having produced, no info available from them.

I think they should be held upright so that the ribbons themselves are
vertical at all times.

B&O didn't actually make those, they just rebadged them. I don't recall
the whole story, but David Royer purchased the rights to the original
Speiden design which the B&O was adapted from and the current Royer ribbons
are mechanically very similar designs but with much better transformers
and magnets.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."