I have a mic I've owned almost 50 years- a Syncron AU7. As near as I have been able to discern, it was (is) the first American-made LDC mic. It is solid state but not phantom. It requires two 8.4 volt batteries to to power the amplifier, and two 22.5 volt batteries to polarize the capsule. Plugging the Amphenol connector completes the circuits to power up. It physically resembles a reduced-size u67. (Further info and pictures can be found at coutant.org. )
I always liked this mike, even though it had no bells and whistles like low end roll-off, output pad, pattern selectivity, etc.
I had a devil of a time tracking down suitable batteries, and then I find it is a high-qualty emitter of a frying sound. The capsule is original, not gold (nickel ?) with blue plastic surround and backplate. It is original, and is covered with what you would expect from that time.
My question: what kind of capsule will adequately perform at the 45 volts of polarization.
My interest in this mic is purely sentimental, though when I used it in the 60's and 70's the general consensus of all who came through the studio was that it sounded pretty good.
