0dbfs
Well-known member
Hi, I have a pair of SDC Tube Mic's exactly like these:
http://www.carillonaudio.com/products/tube/26/carillon-tube-100-kit/
I have purchased AMI Bv13 / T13 transformers and am planning to rebuild these into something different with fixed bias, 5840 tube, and AMI's T13 transformer.
I wanted to make them like a KM54 but there a couple issues with doing that.
1. The KM54 is a nickle skinned diaphragm.
2. The capsule in the KM54 headbasket is isolated such that both the diaphragm and back-plate are electrically isolated from chassis.
3. In the KM54 the backplate feeds signal to the grid and sits about 2.5V above GND while the diaphragm is biased with 40VDC as well as what looks like an NFB path from the plate.
Anyway, the doner-mic has the backplate connected to chassis/GND in the headbasket so it's not isolated.
I have started working this schematic up with (hopefully) some clever ideas borrowed from other mic's. I'll have to work out some component values but you should get the general idea.
I also am interested in using other capsules, or perhaps some sort of adapter to fit other capsules.
Any comments are appreciated!
Best,
jb
http://www.carillonaudio.com/products/tube/26/carillon-tube-100-kit/
I have purchased AMI Bv13 / T13 transformers and am planning to rebuild these into something different with fixed bias, 5840 tube, and AMI's T13 transformer.
I wanted to make them like a KM54 but there a couple issues with doing that.
1. The KM54 is a nickle skinned diaphragm.
2. The capsule in the KM54 headbasket is isolated such that both the diaphragm and back-plate are electrically isolated from chassis.
3. In the KM54 the backplate feeds signal to the grid and sits about 2.5V above GND while the diaphragm is biased with 40VDC as well as what looks like an NFB path from the plate.
Anyway, the doner-mic has the backplate connected to chassis/GND in the headbasket so it's not isolated.
I have started working this schematic up with (hopefully) some clever ideas borrowed from other mic's. I'll have to work out some component values but you should get the general idea.
I also am interested in using other capsules, or perhaps some sort of adapter to fit other capsules.
Any comments are appreciated!
Best,
jb