External Polorisation Voltage ........

[gary o]

Is there any reason not to send 60 to 80 volt from separate power supply to polorise a capsule in  FET a mic circuit like a U87 or any circuit that could bemefit from higher polar voltage....

I know it costs to make supply and extra wire is pain..... Or are there other  reasons to use DC DC converter of just phantom power?

 

[pasarski]

If one builds an external PSU, why use phantom power with it's disadvantages at all then?

 

[gary o]

Well thats my point...... Im thinking about using a power supply built for Elam/M49 mics 120V B+ to send power to a capsule in a KM84 circuit that is using a large diaphram.... was gonna divide the 120VDC into two using 2 X 1M resitors as in the M49 circuit for 60VDC...... shouldnt be a prob should it .......

 

[pasarski]

Well thats my point...... Im thinking about external power supply built for Elam/M49 mics 120V B+ to send power to a capsule in a KM84 circuit that is using a large diaphram.... was gonna divide the 120VDC into two using 2 X 1M resitors as in the M49 circuit for 60VDC...... shouldnt be a prob should it .......

Works if the PSU is regulated. If not, you'd have to adjust the voltage divider. You could power the FET also with that PSU, but for KM84 it wouldn't make a difference. But you could build a "better" circuit. That's what Gus was talking about lot a while ago.

 

[gary o]

Ok PSU isnt regulated its similar to a C12 an old time DIY friend tells me it kinda reulates itself ( I lack knowledge) but it work for my Elam/M49 circuits, I have copied M49 two 1M resistors to divide 120V into two, its working out to 56V at capsule, it seems to sound a little fuller if anything but not a massive amount.....

 

[RuudNL]

Is there any reason not to send 60 to 80 volt from separate power supply...

Don't go higher than 60 volts if you like to keep the capsule in good condition...

 

[gary o]

Thanks RuudNL ....its at 56V at moment..... I thought some capsules went to 80V ?

At 56V there does seem to be a little improvment in sound Im aware I might be imagining it BUT I have a faint hummm with my external 60V wpuld need to address that if Im gonna use external polar power ....

Thanks

 

[pasarski]

If I'm following you right and your PSU outputs 120V to a tube mic, it'll output more if you use it just for polarization because there's no tube drawing current and pulling down the voltage. That's why I asked if it's regulated. Check the voltage unloaded and calculate the divider for 60V from the unloaded voltage.

 

[gary o]

Hi Pasarski the PSU outputs 123V with no mic ..... output is taken across a resistance not sure what this type of supply is called my old timer electronics friends says its a simple but good design as it kinda regulates itself..... I dont know enough..... its unlike a power supply I buld for Maxes MK47 which outputs much higher voltage without the mic connected.... doe this make sense Im not great at explaining.... anywat with two 1 meg resistors across the 123V I get 56V at the junction of the two 1 megs ( like in a M49) Im sending tha 56V thru a wire to the KM84.

Thanks

 

[pasarski]

Cool, guess it's (semi?) regulated then. I like this idea, thinking out of the box

 

[gary o]

Thinking of boosting polar voltage in my KM84 circuit with 9 to 15volt batteries ....... still using the phantom supply just wiring batteries in series with the polarisation voltage..... I should check this doesnt effect the amplifier circuit I guess...