premap front for 60 ohm mic

[user 37518]

I've worked with some B&K mics aswell for instrumentation purposes, they are rather odd, they dont work with the traditional phantom power but rather something like 200V, they have an external supply that feeds the DC to the mics, but the output of the supply is not amplified at all, it has unity gain and the outputs are MIC level BNC unbalanced with an output Z of about 25 ohms, a lot of gain is needed to bring the signal up to an optimum level, I actually ended up using an AD797 in a standard non inverting configuration, the Noise figure is a non-impressive 5dB due to the low source Z, but  it works quite well. I thought of adding a transformer after then BNC output, but I dont want to color the signal even slightly.

 

[kambo]

Which model of B&K did you get ?

still, playing with different microphones and preamps... hard to pick one up... looks like need more than one, depends on
how i would use them!
but, i think i am gonna go with 1/4inch 4939 with 1/4" preamp 100khz mic/micpre.
its kind a noisy compared to 1/2 mics, but on loud source its totally fine....
they do some other 40Khz and 70khz 1/2inch mics..
hopefully, will try those too... 

ps: jensen line trx 11p's r like a copper wire. u dont hear a thing! i used on my tube line mixer.