I am new to this forum. Just found out that there are quite a few threads on the Nakamichi microphones (=Teac, Tascam, Altec, all manufactored by Primo). I would like to modify my own set of CM-300. The output level is too low in my set up. The output transformer reduces the output from 8 to 1.6 mV. Please, look at the schematics below:
A is the original circuitry of the CM-300.
B is a revised circuitry with a raised supply voltage as suggested by Stephen Sank.
C would be the front end of B. Without transformer not the very best for driving long cables. What difference will there be between C and D?
What about E, can it be used? Sure, also problematic with long cables. F is taken from the homepage of Scott Helmke. It uses a P48 phantom power supply. As I would like to run my microphones on internal batteries maybe a P12 would be suitable? Is my schematic G correct? The components are sometimes added, for what reasons? What about the values of the drain and source resistors to suit the 2SK118-O with an Idss=1mA?
Roger Gustavsson