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R/E/P => Klaus Heyne's Mic Lab => Topic started by: srs4164 on November 27, 2015, 04:45:54 PM

Title: AKG C61 work with an AKG N12A?
Post by: srs4164 on November 27, 2015, 04:45:54 PM

Will a N12A PSU power a C61 without modification, or does the extra circuitry for the pattern selector, which a N61A doesn't have, keep this from working?

Title: Re: AKG C61 work with an AKG N12A?
Post by: klaus on November 28, 2015, 03:55:26 PM

The N12A was designed to power the Nuvistor-model C12A. The C61 uses the same Nuvistor with same heater and B+ supply voltages, but a different connector.

B+ (high voltage) is only marginally affected in a C61 when you click through the N12A pattern selector, and only ifyou move the selector after you have calibrated the supply to deliver a perfect 120VDC for your C61. A slight voltage dividing effect will vary a couple of volts of B+ as you click between patterns.

A more permanent solution: disconnect R11 (variable resistor) in the power supply at the the junction of R6, C6 and R7.  At that tap, a wire connects to the pattern selector. No connection, no voltage drain. You effectively have bypassed the circuitry for the variable voltage.