P12 (not T-Power) Phantom from a P48 supply?

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mylesgm

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I've a lead on a few schoeps mics that use P12 phantom which is not T-Power but I can find very little to no info on this and there don't seem to be any commercially available converters for powering these mics from a P48 supply while there are heaps of P48 to T-Power supplies.  Any ideas or leads?

 
mylesgm said:
I've a lead on a few schoeps mics that use P12 phantom which is not T-Power but I can find very little to no info on this and there don't seem to be any commercially available converters for powering these mics from a P48 supply  Any ideas or leads?
The difference between P12 and P48 is the former uses 680r resistors instead of 6.8k, with an open-circuit voltage of 12Vdc instead of 48. The max current is 15mA for P12 vs. 10mA for P48.
Typically, a P12 mic draws more current than its P48 counterpart; the result is that many P12 mics will operate correctly under P48 (the contrary is not true).That's probably the reason why nobody makes adapters...
Can you get some more info about these mics, particularly their current draw? Then it would be easy to evaluate the voltage drop. In case the voltage drop is not enough, resulting in excessive supply voltage to the head amp, there is a risk of damaging components, in particular capacitors that may not be sufficiently rated.
Now, if you look at the Schoeps schemo, and these mics are somewhat related to the CMC5 type, you may see that all versions are quite similar, except for one resistor (R10); instructions are printed on the schemo.
The capacitor is rated 40V, which makes operation with P48 safe, because the current draw is about 9mA, so the voltage drop is 9x3.4, or about 30V, resulting in about 18V at the transistors' emitters.


while there are heaps of P48 to T-Power supplies. 
Really? I'd be curious...
 
It's for the Schoeps CMT34 microphones and there's some info on them here: http://www.schoepsclassics.de/1965_cmt30_40_50.htm
But there's no info on the schoeps website and very little info elsewhere and that info is confusing (you can power them with p48/You can power them with a high current p48 but it will burn out lower current supplies/you can't power them etc).

There are lots of P48-TPower adaptors on ebay, conversion barrels, in-line bricks, etc.  Just search T power adaptor on ebay and see.
 
mylesgm said:
It's for the Schoeps CMT34 microphones and there's some info on them here: http://www.schoepsclassics.de/1965_cmt30_40_50.htm
OK, so that's the one I referred to. I've just posted the schemo in the Technical Documents folder.
On P12/P24 versions, R10 is shorted, for P48, you just need to remove the short.


But there's no info on the schoeps website and very little info elsewhere and that info is confusing (you can power them with p48/You can power them with a high current p48 but it will burn out lower current supplies/you can't power them etc).
Don't believe all that's on the internet... :)


There are lots of P48-TPower adaptors on ebay, conversion barrels, in-line bricks, etc.  Just search T power adaptor on ebay and see.
I didn't know there was that much...
 
abbey road d enfer said:
OK, so that's the one I referred to. I've just posted the schemo in the Technical Documents folder.
On P12/P24 versions, R10 is shorted, for P48, you just need to remove the short.
Really? It's that simple? Does that solve the issue of higher current draw?

abbey road d enfer said:
Don't believe all that's on the internet... :)
NEVER!!
 
mylesgm said:
Really? It's that simple? Does that solve the issue of higher current draw?
With the mod the current draw is 4mA.
Anyway, without the mod, the current draw would be 9 mA, which should not be an issue; it may have been an issue at the time, before the P48 norm was modified to increase current capability from 5 to 10mA.
 

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