WhitakerAudio JC Whitaker 20 W Stereo Integrated Audio Amplifier, Manual

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20 W Stereo Integrated Audio Amplifier
left channel gain control on the preamplifier PWB (R157) to produce 10 V rms output. With
a 1.0 V rms input, the typical position for R157 is fully clockwise.
4) Adjust the generator to produce 0.0072 V rms at 1 kHz. Move the Balance control to the
center position. Move the generator to the left channel Phonograph input. Switch the Input
control to Phonograph.
5) Adjust the Left Phono Level control (R120) on the preamplifier PWB to produce an output
level of 10 V rms. The typical position for R120 is 2/3rd clockwise.
6) Move the voltmeter from the left channel speaker terminals to the right channel speaker
terminals. Move the signal generator input from the left channel Phonograph input jack to
the right channel Phonograph input jack. Confirm that the signal generator is still set to
produce 1 kHz at 0.0072 V rms.
7) Adjust the Right Phono Level control (R110) on the preamplifier PWB to produce an output
level of 10 V rms. The typical position for R110 is 2/3rds clockwise.
8) Move the signal generator to the Front Aux input jack. Apply a 0.3 V rms signal at 1 kHz.
Set the volume control fully clockwise. Set the Balance control to center. Switch the Input to
Front Aux. Adjust the right channel buffer gain control R164 to produce 10 V output at the
right channel speaker terminals.
9) Move the signal generator to the left channel of the Front Aux input and maintain the 0.25V
rms 1 kHz signal. Move the voltmeter to the left channel. Adjust the left channel buffer gain
control R171 to produce 10 V rms output at the left channel speaker terminals.
10) Remove the input signal and disconnect power from the amplifier.
During adjustment of the preamplifier gain levels, the proper positions for the on-board
potentiometers should be nearly identical between channels. Minor gain variation between
channels is normal.
The foregoing settings should provide a good starting point for use of the amplifier. Touch-up
adjustments using program material can be made later if needed. Attach the bottom chassis plate
using the four #6 sheet metal screws.
The preliminary tests and adjustments have now been completed.