Variable Pattern Mic Question.

Well, having looked at some Neumann and AKG tube mic power supply schems, I notice that they all use a row of resistors connected to a rotary switch but if I wanted to use a pot instead of all the resistors, whats the best way to calculate the value?
Would it have to be the same as the combined resistance of the individual
fixed resistors in the chain?
Comes out at a really odd value if it's say 8x 5.6k.
Sorry if this is a really dumb question.

Thanks

Any ideas or is this a sillier question than I realise?
Quite possible.

Thanks

If the switch is set up as a tapped voltage divider - and it probably is - you can substitute it with a pot.

8 x 5600 = ~45000 Ohm. Use a 50K linear pot. You'll be fine.

Peace,
Al.

Not silly. But resistor value is kinda unimportant - it is just a potential divider, you don't draw no current... Just keep the overall resistance high enough not to load the supply..

Jakob E.

[quote author="gyraf"]resistor value is kinda unimportant[/quote]

Unless there's a resistor already in series with the voltage divider to bring down the maximum polarization voltage. E.g., If you have a 200V supply, but want a maximum of 100V going to the capsule, you would strap a 100K resistor in series with a 100K pot across the power supply, to get a variable voltage between 0V and 100V. Change the resistance of the pot, and the voltage range changes with it.

Peace,
Al.

[quote author="alk509"]If the switch is set up as a tapped voltage divider - and it probably is - you can substitute it with a pot.

8 x 5600 = ~45000 Ohm. Use a 50K linear pot. You'll be fine.

Peace,
Al.[/quote]
AKG C12 use 8x56K on their pattern switch.

Yippeee!!!!

Thanks guys.
As usual I thought it was far more complicated than it actually was.

Huge thanks.