AM 320-01-808
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11. AF 40 (Audio Board)
The output signal of EF 40 (ORGAN 1, ORGAN 2) is led
to the AF 40, controlled in its volume by IC 1, a VCA
(voltage-controlled amplifier); the volume level is de-
pendant upon the control voltage at pin 5 or 10. This
voltage is adjusted with the swell pedal (05 3), the control
current of which (0 to 0.6 mA) is converted into a voltage
of 0 to 2 V by two OPAMPs (IC 10).
With P 3 you can adjust the minimal volume level that can
be heard with the swell pedal at minimum volume. The
LED will be illuminated as soon as the control voltage
reaches 2 volts which should be the case when the swell
pedal is fully depressed.
The organ signal now adjusted in volume is routed to the
reverb summing amp IC 15 (via R B & R 11) to the chan-
nel amplifier IC 12 left and right (via R 9 & R 12) and to
the multi-channel output (via R 7 & R 10).
The rhythm signal from the drum board DSP 160 uses a
similar path; the only difference is that the control signal of
the VCA (IC 3) consists of the control voltage VOLRH and
a small portion from the swell pedal.
The reverb summing amp leads the organ/rhythm signal to
the reverb board DH 11 where the signal is reverberated
and - via lines REV 1 and REV 2 - sent back to the AF 40.
This signal's amplitude is controlled by IC 7 and added to
the original signal via R 39 & R 40.
The organ/rhythm/reverb signal (AF 4/01, AF 4/02) is
routed via the main volume control on the connection panel
CB 45 (where the overall volume is adjusted) and returns
on lines AF 40 Ii and AF 40 12.
Now the signal is split up; one portion to the headphone
amplifier (IC 14, T 1-T4) and one portion to the tone
control stage (IC 9, P 1, P2).
The tone control section is followed by a relay with which
the audio signal can be switched off.
The remaining portion of the circuitry is responsible for the
audio supply of the Leslie. One half of the VCA (IC 11)
routes the Leslie signal (W 1/LES, W2/LES) to the Leslie
amplifier (IC 15, T 5, T 6), depending on the swell pedal
position, while the other half adds another reverb signal
generated by an external reverb unit.
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