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I
N T R O D U C T I O N
The Hafler P4000 is a three rack height, two channel professional power amplifier suitable for use in any
situation where a moderately powered compact amplifier is required. The P4000 is particularly attractive for
use in monitoring situations. Our trans•nova circuit topology and MOSFET output stage ensures trouble-free,
long term operation and is backed by our five year warranty.
This manual contains information on using the P4000 amplifier. It is organized into three main sections.
"Installation" covers the location and connection of the amplifier in the system. Like many precision
components, careful attention to the initial setup can yield dividends in higher performance and trouble-free
use. "Operation" covers the controls and features of the amplifiers and how to use them to get the best effect.
The "Technical Reference" section contains field service information; in addition to the schematic and parts
list there are block diagrams and circuit operation explanations useful for technicians. We strongly urge
reading over the Installation and Operation portions of this manual before putting the amplifier into service.
The circuitry used in the Hafler Professional power amplifiers is our trans•nova (TRANSconductance Nodal
Voltage Amplifier, U.S. Patent 4,467,288) circuit. The P4000 also utilizes our proprietary DIAMOND
(Dynamically Invariant AMplification Optimized Nodal Drive, patent pending) transconductance driver stage
which combines the linearity of Class A operation with the current headroom of a Class B system. When
combined with the robust output stage used in the P4000, DIAMOND yields lower high frequency distortion
without the sonic degradations associated with increasing the negative feedback. We have been using
MOSFETs in our power amplifiers since the 1970's. During this time they have proven to be extremely fault
tolerant, even in abusive situations. This ruggedness enables the amplifier to drive reactive speaker loads
without the performance and sound degradations imposed by elaborate Safe Operating Area protection
schemes.
Other specialized circuits which prevent damage to the amplifier and speakers have been carefully imple-
mented. A soft start circuit prevents sending potentially destructive turn-on and turn-off transients to the
speakers. A thermal sensing network continuously monitors the heatsink temperature and shuts down the
amplifier to protect it from excessive operating heat. The need for internal fuses has been eliminated; a sensing
circuit monitors the output and shuts down operation when it detects a short at the output.
Each channel of the amplifier has been built as a self-contained module. This modular arrangement simplifies
construction and improves service accessibility. The circuit board assembly makes extensive use of surface
mount components in the low power portion of the audio circuitry. Automated equipment is used to place and
solder the components which yields greater uniformity and reliability.
The front panel has controls for input level adjustment and the power switch. In addition, LED indicators give
a visual representation of the operating status of each channel. The THERMAL and SHORT indicators light to
show when these protection circuits have been activated. The CLIP indicator helps prevent damaging the
speaker by showing when the amplifier is overdriven. The SIGNAL indicator lights to show the presence of an
audio signal.
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