|Here's the KISS rig's
microphone input-preamplifier and balanced modulator
The JFET input-amplifier stage is under test for the first time.
|The LF386 mini-DIP 8-pin op-amp socket is now mounted, along with its miniature gain-setting pot.|
|The JFET is coupled to the
op-amp, and power (+12-V) is simultaneously applied to
both stages for preliminary testing.
Oscilloscope probes are attached to the input stage (right-hand probe) and output coupling capacitor (probe at upper left-hand corner).
|It's a long way from Shockley,
Bardeen, and Brattain.
A 1-kHz tone is fed into the JFET input coupling network (top trace). Its level is about 100-mV.
The bottom trace shows the output of the op-amp into a 10-kohm temporary resistive load. Output level across this load is about 8 Vpp. This test was repeated at increments from 100-Hz to 5-kHz.
|Here's the messy workbench (ca. 2005) after melting solder and making the microphone amplifier/buffer preliminary tests.|
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