Audio Pro B2-50, Руководство по обслуживанию

Страница: 7 / 15

1.6 Power Amplifier
The input signal to the Power Amplifier is DC decoupled by
capacitor C414, and is amplified linearly to the output (test
point G).
The output signal is fed back negatively to the input via R511,
C503.
When the output signal is large, negative feedback is also
obtained via a diode - resistor network. The amplitude of the
output signal is compared to the supply voltages (+40 V) in this
network, and about 2 volts before clipping, the output signal is
rounded off by the diode network so clipping will be soft.
The differential input stage (V503, V506) is supplied via a
current generator (V504). Transistors V501, V502, V505 form
a current mirror, so the output stages from V507, V509 are
symmetrically driven.
The output stage is of triple darlington type with transistors
V512-V517. AC gain is 1. V508 senses the temperature of the
output transistors and assures constant bias current.
V510 and V511 filter the supply voltages to the input stages,
removing hum and transients.
NOTE: If there is a"click" in B2-50 when it is switched on,
the cause could be a short circuit in one of the tran-
sistors V510, V511.