12.1.4 Operation
It will be seen that the resonant circuit selected by S1, together with a series
resistor R2, can by means of S1, be connected across various amounts of either the
forward or the feedback circuit to give 2, 4, 6, 9 or 10dB of boost or cut at the
resonant frequency.
12.1.5 Output
The output is taken direct from the emitter of VT2 which has a potential of
about +0.5V. the output impedance is low. The output will deliver at least 1.8V
r.m.s. into 3k
Ω
.
The output is in anti-phase with respect to the input.
12.2 Bass
12.2.1 Component parts
There are two sections the complete circuit being shown on Drawing No.
AE.202. The active and reactive components are assembled on Board B51/3 as
used for the presence circuit.
The amount of bass is determined by switch S1 which is identical with switch
S2 used in the presence circuit.
12.2.2 Active Circuitry
This is identical with that used on the presence board with the exception that
the input and feedback capacitors C1 and C4 are each 4.7
µ
F.
This is necessary to prevent any tuning effect when either of them is in series
with L1.
12.2.3 Reactive Component
The frequency of operation is determined by a Ferroxcube Inductor L1 having
an inductance of 1.93H. This, with its resistance built out by R2 (750
Ω
) yields a half
lift or cut frequency of 500Hz.
12.2.4 Operation
Switch S1 connects L1 and R2 in series across various amounts of either the
forward or the feedback circuit to give a step function having a total boost or cut of
2, 4, 6, 8 or 10dB.
12.2.5 Output
This is identical with that of the presence circuit described in 2.1.5.
