Crumb wrote:
Hi;

I have an old RCA ribbon mic in which I want to experiment with better
transformers. I have a few high-end matching transformers which will
match 1 or 2 ohms to 50, 150, 300, or 600 ohms. The freq response of
these transformers is 10-50KHz 1dB. The problem is the transformer is
approx a 4" cube. Is it feasible to run a balanced line directly from
the ribbon element to this transformer? OR, at this low level is the
common mode rejection of noise beyond the precision of the cable and
transformer involved?

The real answer is to just TRY it! Generally older ribbon mics
were built with a matching transformer right in the mic. That is
because the ribbon impedance is VERY low. I'm not sure 1-2 Ohms
is low enough. Because of that VERY heavy wire needs to be run
from the transformer to the ribbon element. All resistance quickly
adds up to heavy losses in signal.

If it were me, I'd try mounting the transformer right on the mic
stand. Preferably as close to the mic as possible. You'd try to
use as heavy a flexible wire as you can find to run between the mic
element and the tranformer (preferably not through a connector).
Then see if that works. If so, you can start backing off and see
what happens. Try inserting a connector at the mic. Try running
longer wires. Eventually try putting the transformer at the far end
of the mic cable. Each change should give you a feel for what you
can and can't get away with.

I know that in some of my ribbon mic experiments I was pretty much
surprised at how low the impedance of the ribbon was and how much
loss you got if the transformer didn't match it correctly.

Benj

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