Revox B 242 Owners Manual

Page 1

SW3 EE REVox', ;
3242

Bedienun s- and
Servicean eitung

Operating and
Service Instructions

Mode demploi et
instructions de service

Page 39

2.2 POWER AMPLIFIER

DH +_- ________________________ m L; 4 ~~~~~~ [1r @

LP-FILTER
0.1 Hz

IDLE CURRENT
ADJUST

RELAIS-L .
> mater-CD
pm __._..,____._ 0/0 mm
cmcun
(D @ 1 ® a} e - Q)
i
LH-L [> "A [> > : 5 «96 mun-p OUT'LEFT
DIFFERENTIA 7,, W, l
mamas mum? STAGE PMER run-nun OUTPUT
sue: nuts
1 - rean-
HEAT-L 4- _ 2] rifi-VEACK 4-7 -- «www ~7
' rm: crucun
TEKFERATURE
ssuson

Only the leftehand channel is described since the right-hand
Channel is identical
The input signal (CH-L) is taken through the cascade differential
amplifier (D. The driver stage @ comprises two puslrpull cascade
current sources
The AB class output star 9. (-1) with its 2 x 3 parallel connected power
transistors produces 2 O W driven into 8 Q or 4 Q (switchselect-
able). The protective clrcurt (D measures the collector-emitter volt-
age and the emitter current of the power transistors. It protects the
output stage from overloads by reducing the modulation,
The quiescent current of the tail transistors is set with blookét The
PON-L Signal switches the supply voltage of the driver transistors
on and oft
The RL.C output filter (n) keeps capacitive load impedances away
from the amplifier at elevated frequencies.
The output relay (I) disconnects the load from the amplifier output if
the heat sink is overheated. if DC voltage is present on the output.
and during the power-on delay.
The NTC resistor 6) measures the heat sink temperature and pro-
duces the HEAT-L signal,

17