Audio Amplifier Circuit - Eiki ESL SERIES Service Manual

C.
Audio Amplifier Circuit
The input from the solar cell or magnetic head is accomplished through the 5 pin connector
and switched to their appropriate impedance loading circuit. Models with optical sound
capabilities only have amplifiers without the opt/mag switch. The input signal is routed
through the MIC jack and coupled to IC-1 (AN-370) via capacitor C-3 and resistor R-6.
R-8, 9 and 10 C-8 and 9 form the opt/mag input equalization network, with feed back from
the tone controls V R-1 and V R-2.
Tone control equalization is accomplished by R-13, 14 and 15 and capacitors C-13, 14, 16
and 1 7.
From the tone controls the signal is coupled to the pin 2 of IC-2 (AN-370) via C-18 and R-15,
and IC-2.
The output of IC-2, pin-6 is coupled through C-23 and R-20 to VR-3 (volume control}. The
wiper of VR-3 is coupled through C-25 to the base of TR-1 amplified and coupled to the base
of TR-2, from TR-2 the signal is phase split to intermediate drivers TR-3 and TR-4 respec-
tively. The final complimentary drivers TR-5 and TR-6's emitter are coupled to R-36 and
R-37 through C-33. The final driver to the speaker jack is from the negative side of C-33 and
ground. Note that the output to the rear cover speaker jack is switched through the external
speaker jack.
600 ohm un-balanced aux line output is available through the external speaker jack provided
a "stereo" 3 conductor phone plug is used.
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