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A32 Functional Description
Features
The Primare A32 power amplifier is a fully balanced design, this means that the negative
speaker terminals are active, not ground as on an unbalanced design. When performing
measurements, test equipment (such as Audio Precision) that can handle balanced
amplifiers must be used.
The input impedance is 15K and the gain is 26dB. It is possible to obtain just above 250
undistorted watts at an 8R load (both channels driven). The frequency response are flat,
the A32 will drop down only -2dB at 100Khz.
Standby
The A32 is equipped with two standby modes, where standby mode 2 is the power save
mode. In power save mode only the standby circuit will be powered by the small standby
transformer placed on the digital PCB.
Digital control and monitoring
When power is first applied and the standby button on the front panel are pressed down
the A32 are going to initiate the startup sequence. Relay K1 will be turned on where after a
small delay will follow before relay K2 goes active to disable the inrush limiters. At the
same time bias are turned on by shutting down the voltage supplied to the optocouplers on
the amplifier channels. After a 20 second startup delay for the amplifier to settle down the
speaker relays are turned ON. During the startup sequence all safety parameters such as
DC-offset and fuses will be monitored, if an error is spotted the amplifier will refuse to start
and the standby LED will flash rapidly to indicate that an error has occurred. The error
code can be read out by pressing the error check switch (SW1). Description of the error
codes can be found on the next page.
If the standby switch is pressed when the amplifier is in operate mode it will go to standby
mode 1, which means that bias and speaker relay will be switched off. The standby LED is
going to half light intensity to indicate that the amplifier is in this standby mode.
If the standby button are pressed down for more than one second the amplifier are
shutting down into standby mode 2 which means that bias, speaker relay and the two
power relays K1, K2 are switched off. Only the standby circuit is still powered consuming
just a few watt of energy.
Temperature protection
When temperature has reached 70 centigrade at the temperature sensors the speaker
relay and bias are going to be switched off, when the temperature have decreased 10
centigrade the A32 are going to be restarted. In practice this will mean that the warmest
part of the heatsink will be around 75-80 centigrade when over- temperature protection
cuts in.
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