Crown m120 Manual De Usuario

For the sake of simplicity, only channel one of 
the amplifier is described.
 
Signal is presented to the M120 and M240 
through one of three connectors when using 
the standard input module. Each channel is 
outfitted with a balanced XLR / phone jack, and 
a barrier strip. These connectors are wired in 
parallel, which allows daisy chaining when 
needed. The signal is then converted from bal-
anced to unbalanced in the Balanced Input 
Stage where it also receives RFI protection. 
Signal then flows into the Variable Gain Stage 
where the front panel level controls are allowed 
to affect the gain. 

Following this stage, the signal is put under the 
control of a full-time compressor circuit com-
prised of a symmetrical window detector, a 
buffer amplifier, and the gating op amp which 
uses several small components to set the com-
pressor’s attack and decay characteristics. The 
actual compressing is accomplished by an 
opto-isolator which affects the gain in the sig-
nal path.

The signal next enters the main amplifier error 
amp where it is mixed with a small portion of 
the output signal in such a way as to control the 
amplifier’s overall output performance. 
Following the error amp is the LVA stage, which 
is where the low-voltage referenced signal gets 
translated to the output high-voltage rails. The 

last voltage amplifier, in conjunction with a 
bootstrapped current source, drives both pre-
drivers and the bias servo. The bias servo is 
mounted in such a way as to translate the out-
put heatsink temperature into a controlled bias 
current to prevent thermal runaway and hold 
the amplifier’s notch distortion to a minimum.
The predrivers provide enough signal to acti-
vate the drivers, which together operate in the 
class AB range. For the major output current 
requirements, the drivers feed the various num-
bers of paralleled output transistors which 
operate in a class B mode. This we call the Tri-
ple-Deep Darlington Output Stages.