Schoeps

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Thats an interesting one thanks Tony , I like the way the designer avoids cathode resistor and cap by tapping the heater voltage for grid supply, U47 does something similar and I suspect it may well contribute to the gracious overload .
 
The late Ing. Dr. Schoeps also used the DC heater voltage biasing on some versions of the M221 mic using the AC701 tube... I like having the bias fixed rather than dependent on the current through the tube... I didn't see any heater voltage regulation...but 6AU6 tubes don't cost as much as a AC701....

I like the Neumann NKM supply...both the heater and HT voltages are regulated.  I like the way the HT sees the 150B2 regulator tube first...voltages across the capacitors are held constant...  A clean modification to run up the heater voltage slowly and regulate it can be made to those old supplies...
 
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