Condenser mic capsule polarizing supply

[DOSCAT]

Hi guys i just finished building my first Large diaphragm condenser mic, and I'm starting work on my second, but I have a problem. My first was a tube design and with that I had a 100v supply to use for polarizing the capsule, with my second mic I'm going for a phantom powered fet design which does not have a convenient 100v supply.
I'm no that experienced with DC/DC converters, so could any of you give me some advice? I need to step up 48v phantom power to at least ~80v preferably closer to 100v, but i only need to draw a couple of miliamps at the most.

[Osvaldo de Banfield]

I have a circuit to convert usual 24V to 100V for industrial use. I have made 2 of them, and none has failed. It uses a 1mHy ferrite core rescued from PC monitor, a UC3842, a IRF510 or similar, a diode, and few resistors and capacitors. The board is 3cm per side. It has a 30mA output capacity. I can draw and send you next week, if you can wait for it.

[DOSCAT]

That sounds perfect thanks.

[nazaroo]

Originally Posted by DOSCAT

Hi guys i just finished building my first Large diaphragm condenser mic, and I'm starting work on my second, but I have a problem. My first was a tube design and with that I had a 100v supply to use for polarizing the capsule, with my second mic I'm going for a phantom powered fet design which does not have a convenient 100v supply.
I'm no that experienced with DC/DC converters, so could any of you give me some advice? I need to step up 48v phantom power to at least ~80v preferably closer to 100v, but i only need to draw a couple of miliamps at the most.

I was wondering why you felt you needed more than 48v for polarizing the diaphram? What is the advantage there?

Also, aren't you worried about raising the noise-floor by adding more active circuitry to a circuit which by nature
will be the most difficult and exacting of designs to keep quiet?

If an ultra-low noise design is needed anywhere it would seem to be here...?

What special steps did you take in your tube circuit to drop the noise floor?

[SY]

And what kind of capsule are you using?

[DOSCAT]

To answer bothe questions I'm making my own capsules from scratch, and I found by experimentation that the normal polarizing current of ~60 or so volts used by most large diaphragm studio condensers was giving me to low a gain do to my lack of being able to build the capsule as precise as needed.

[nazaroo]

Originally Posted by DOSCAT

To answer bothe questions I'm making my own capsules from scratch, and I found by experimentation that the normal polarizing current of ~60 or so volts used by most large diaphragm studio condensers was giving me to low a gain do to my lack of being able to build the capsule as precise as needed.

I'm surprised that large diaphrams use more than 48 volts,
since this is the Newmann standard, and most 3rd party phantom supplies use 48 or less!.

But do you refer to microphones which provide their own proprietary cabling and power supplies?
I did not know they pumped in more than 50 volts to the diaphrams.

I knew that many tube circuit preamp sections (built into the mics) required anywhere from 150 to 450 volts DC for the tubes,
but was unaware that they fed much of this to the diaphrams as well.

Can you give an example of a large-diaphram microphone (0r two) that actually apply high voltage to the condensor capsule?
and what exactly are the voltages applied?