PassLabs-AlephP1.0 preamp.pdf | | Service Manual for Aleph P Version 1.0
PRODUCT DESCRIPTION The ALEPH P is a high performance Mosfet Class A audio preamplifier, intended for maximum performance in reproduction of music. It is a simple design, having only a single balanced gain stage consisting of a balanced pair of power Mosfets operated without feedback. The Mosfets are biased by resistors and loaded by resistors, will accept either single-ended or balanced input while delivering single-ended or balanced output. To best understand the operation of the preamplifier, refer to the schematic of basic gain stage. Q101 and Q102 form the active portion of the gain stage, with Q101 receiving the + balanced input signal, and Q102 receiving the balanced input signal. Reference voltage A of 18.2 volts is used to bias the gates of the Mosfets through R109 and R110, and the inputs are capacitively coupled through C105 and C106. R111 and R112 are employed to prevent parasitic oscillation, and Z101 and Z102 protect the Mosfets fro |