Crown Audio CE2000TX User Manual

For the sake of simplicity, only channel one of 
the amplifier is described. 

Signal is presented to the CE 2000TX through 
one of three connectors when using the stan-
dard 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 balanced 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.

Next the signal enters the error amplifier circuit, 
where it is mixed with a small portion of the 
output signal in such a way as to control the 
amplifier’s overall output perfomance.

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 
bootstrap current source, drives both predriv-
ers 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.

The output transistors are protected by the Time 
Dependent Voltage & Current circuit. This cir-
cuit protects the devices from extending 
beyond their safe area of operation, but allows 
the devices to provide high bursts of peak 
power with music, allowing your amplifier to 
deliver more punch. When all is said and done, 
this amplifier output topology offers a good 
combination of low quiescent amplifier heating, 
great distortion performance at high powers, 
and relative simplicity, with impressive reliabil-
ity and value.

All output power is delivered through 4-circuit 
Speakon

®

 connectors. These connectors have 

been wired in such a way as to allow you the 
most versatility. The Channel 1 and 2 connec-
tors are cross wired so you can cover all 
options, from dual cable stereo (typical), to 
Bridge-Mono in one connector, to running a bi-
amp speaker with one amplifier and one cable 
per speaker cabinet.

The output relay, in conjunction with input sig-
nal mute circuit, assures the amplifier will be 
well-behaved during turn on and off. In the 
event of an amplifier output failure, a triac will 
activate to turn off the offending channel and 
protect your speakers.

The turn on delay circuit functions to keep the 
output relay open until all the voltages are up 
and stable, both in the amplifier, and in all the 
components in the system ahead of the 
amplifier.

Heatsink temperature is monitored by a thermal 
probe attached to the heatsink. As the tempera-
ture rises, the probe sends a proportional cur-
rent to the proportional speed fan circuit which 

starts the fan. Should the power transformer 
reach its maximum safe temperature, an inter-
nal thermal switch opens and the fan circuit 
turns on full speed to quickly cool down the 
amplifier. It also disconnects the load via the 
output relay, removing any output current and 
further speeding a cool-down cycle. Extra care 
was taken during the design stage to set this 
point both to protect your investment and to 
guard against nuisance tripping.

Whenever the heatsinks or the transformer 
reach a maximum temperature, or during the 
normal turn-on delay window, the front panel 
Fault LEDs will blink to get your attention. 

A modular jack is mounted on the back panel 
(same type as used on telephones). Pins 2 and 
5 are connected to an opto-isolator which is 
always in a low-resistance state whenever the 
unit is on and happy. Should a fault be detected 
or should the amplifier lose AC power, the 
opto-isolator will change to a high resistance, 
allowing the user to remotely detect the status 
of the amplifier.

The Signal Presence Indicators tap the signal 
chain just before the level controls and prior to 
the power amplifier chain. They are not ampli-
fier output indicators and should only be used 
to indicate the presence of signal to the ampli-
fier front end.

The Clip light is driven from the output of the 
compressor circuitry and lights to indicate the 
onset of audible distortion.

The Power LED is driven from the low-voltage 
supply.

A positive and negative regulator form the ±15-
volt power supplies. Add to that the main trans-
former, a full-wave bridge rectifier, and high 
energy electrolytic to form the main power sup-
ply. They are protected by the front-panel line 
circuit breaker and controlled by the front-panel 
power switch.