PassLabs-Aleph4 pwramp.pdf | | Pass Laboratories Aleph 4 Service Manual
Rev 0 8/18/1997
Aleph 4 Service Manual. The Aleph 4 is a stereo 100 watt audio power amplifier which operates in single-ended class A mode. The Aleph 4 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 3 amps. The voltage rails of the supply are at 48 volts, and each channel draws approximately 250 watts. Fig. 2 and 3 show the actual schematic for the amplifier. F1 is a slow blow fuse, set at 8 amps for 100-120 volt operation, and 4 amps for 220240 volt operation. S1 is the power swit |