|PassLabs-Aleph3 pwramp.pdf||Pass Laboratories
Aleph 3 Service Manual
Aleph 3 Service Manual.
The Aleph 3 is a stereo 30 watt per channel audio power amplifier which operates in single-ended class A mode. The Aleph 3 has only two gain stages which are biased by current sources. Because of the inherent simplicity of the circuit, it is easy to understand and repair. There are no adjustments. Figure 1 shows the simplified schematic of the amplifier. Two p channel Mosfets form an input differential pair biased by a current source operating at about 20 ma. The drain of the input Mosfet is attached to the gate of an n channel power Mosfet which forms the active output stage. It is biased by a current source at slightly greater than 2 amps. The voltage rails of the supply are at 25 volts, and each channel draws approximately 100 watts. Figure 2 shows the actual schematic for the power supply and one channel. F1 is a slow blow fuse, set at 4 amps for 100-120 volt operation, and 2 amps for 220-240 volt ope|