DC Voltage Doubler From Phantom Power

[sr1200]

I'm trying to figure out the best way of going about getting somewhere near 100v to polarize an old mic with the least amount of components.
Can I build something to double the phantom source, or should i build a dedicated power supply? (was thinking a DC-DC boost, but cant find one that will take 48v, but could knock down the 48 to something lower to work with the constraints of something like a UC3843/UC3845.
Other details: Its an old Grundig Mic that needed around 100v to polarize but didn't need a "pre" pre.

 

[ccaudle]

Don't forget that the 48v is sourced through 6.8k resistors, so it is not actually 48V available to use once you start drawing any current.
If you want something simple Analog Devices has some high voltage charge pumps which may work. Might depend on how "near" to 100V you actually need, but doubling voltage is pretty straight forward with a charge pump.

 

[ruffrecords]

Many condenser mics have a simple very high frequency dc/dc convertor based on a few CMOS gates.

Cheers

Ian

 

[sr1200]

Don't forget that the 48v is sourced through 6.8k resistors, so it is not actually 48V available to use once you start drawing any current.
If you want something simple Analog Devices has some high voltage charge pumps which may work. Might depend on how "near" to 100V you actually need, but doubling voltage is pretty straight forward with a charge pump.

I have no clue how much current this would draw. The high end of things pulls 10mA (earthworks). Since this thing is probably in the neighborhood of 70 years old, there isn't much documentation on it. The capsule supposdly has a 50-15K response. Im just really curious as to what it sounds like more than anything. Not expecting anything great at all.

 

[sr1200]

Many condenser mics have a simple very high frequency dc/dc convertor based on a few CMOS gates.

Cheers

Ian

Anything you know of that gets up to about 100V?

 

[ruffrecords]

Anything you know of that gets up to about 100V?

The Rode NT1A for example creates 73V from an internally derived 15V supply.

Cheers

Ian

 

[ccaudle]

Anything you know of that gets up to about 100V?

The design is scalable, it is a CMOS gate configured as an RC square wave oscillator, and the AC waveform drives a diode/capacitor ladder to form double, triple, quadruple, etc. voltage.
This is a copy of the article which inspired most of the designs:
https://gyraf.dk/schematics/Voltage_multipliers_with_CMOS_gates.pdf
You can make that style of design with one or two gates if you want to use single gate packages and really save space, but when the original article came out single gate packages were not available, so using hex inverters was an easy way to also get additional current capability (which isn't needed if you are just biasing a microphone condenser capsule).

Its an old Grundig Mic that needed around 100v to polarize but didn't need a "pre" pre.

By using the term polarize I assume you mean it is a condenser mic, but what do you mean by it doesn't need a pre pre? Any condenser mic needs a buffer stage because of the high impedance of a condenser capsule. Or are you referring to something else?