Crown PSA-2 Service Manual

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7.13 Theory of Operation
General
The Crown PSA-2 and SA2 are two unique power
amplifiers which incorporate revolutionary design
concepts as well as high performance technology. Much
product research was done prior to the actual production
of these units. For example, self analyzing protection
circuitry was needed in order to meet the demanding
headroom requirements of very low impedance loads
(usually the result of paralleling speakers). Modular
internal construction was also needed in order to make
servicing more time-efficient especially for those users
involved in commercial sound. Delayed power-up and
low frequency (including DC) protection is a feature long
requested by loyal Crown users. For the cosmetically
sensitive audiophile, an elaborate dual function LED
display was developed and made standard on the SA2,
but also available for the PSA-2D and PSA-2DX.
As well as the above mentioned features, many “pro-
oriented” circuits such as balanced inputs, internal
crossover capability, limiter-compressor and remote-
control power capability were added to the PSA-2.
The SA2 and the PSA-2 amplifiers from Crown's
standpoint (as also from the customer's) were well worth
the many months of design research and hard labor.
Principles of Operation for the PSA2/SA2
Because the PSA-2/SA2 circuitry is different from any
other previously designed Crown amplifier, the following
explanation is provided in hopes that the service-person
will find it less confusing.
Shown in Fig. 7.32 is a diagram of the output
configuration used most commonly in all other Crown
stereo amplifiers. Note that the ground side of the load is
connected between the positive and negative Vcc supply.
In Fig. 7.33 the output configuration used in the PSA-
2/SA2 is shown. This topology is commonly referred to
as “the low side of the bridge” circuit. With this
configuration, the load terminals are reversed with
respect to ground (ground not connected between the
positive and negative Vcc supply). This was done with the
intent of making the output stage more readily controlled
and observable to the voltage amplifier stages and
Fig. 7.32 Common Output Configuration
OUTPUT
Fig. 7.33 SA2 Output Configuration
7-26

Crown PSA-2 Specifications

General

Brand	Crown
Model	PSA-2
Category	Amplifier
Language	English