FiveFish Studios NK-72DI, Инструкция по сборке

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Copyright © 2016 FiveFish Audio NK-72DI Mic DI Assembly Guide
6. VOLTAGE OFFSET ADJUSTMENT
For best performance and maximum headroom, adjust DC voltage offset at output of Discrete OpAmp to Zero (0) Volts DC.
NOTE: Adjust RTRIM trimmer for closest to 0 Volts DC. Offsets of a few +/- millivolts are fine (less than 1mV is even better).
Several hundred millivolts is not acceptable.
While nothing bad will happen if you skipped this voltage adjustment procedure, (we have capacitor C19 to block any DC
voltage from reaching the output transformer), adjusting for minimum DC offset at this stage minimizes or removes any
popping sound when changing the gain selector switch (i.e. if you used the optional Selector Switch upgrade). But removing
any DC at this point will also help the potentiometer, and avoid any “pops” down the road when the potentiometer gets dirty or
it’s tracks worn out.
To perform this adjustment step, power must be
applied to the module. See section 11 for pinouts
on where to apply the V+ and V- voltages, and
ground connection.
** This step obviously needs a dual power supply. One can use a
500 rack or lunchbox to get power, but without a 3rd-party extender
card, it may be difficult to apply power to the module.
Connect the positive/red lead of your multimeter to
the OpAmp OUT pin as shown in the picture on the
right.
Connect the negative/black lead of your multimeter to
Ground. (See section 11 for pinout/location.)
Adjust trimmer RTRIM (located just beside the
OpAmp) and turn the screws until you can get as
close to 0 Volts DC, as best as you can.