A DIY version of the excellent Pass Labs XA series amplifier
http://www.facstaff.bucknell.edu/esanta ... eph-x.htmlIntroduction and Acknowledgements:
This project was made possible through the generous assistance of Nelson Pass, Grey Rollins, Hifizen, Carpenter, William, and the rest of the community at DIYAudio.com. The notes on this page (50+ pages should you decide to print this...) are a combination of my own experiences and a synthesis of those reported in the threads listed below. This amplifier is a DIY effort to duplicate the exceptional ~$15,000 XA line of commercial amplifier offered by Pass Labs. The XA series amplifier combines the best features and performance characteristics of the legendary Aleph series and the highly acclaimed X series amplifiers (see the passlabs.com web site for more information on these). A number of people at DIYAudio contributed to the circuit design, the design and production of printed circuit boards, as well as construction and testing advice (special thanks to Magura and William!). This particular design is not so much a "project" that comes with a schematic, parts list, and step-by-step building instructions but rather is an open design that can be relatively easily be scaled to meet any set of output requirements dictated by your particular set of speakers and listening preferences. For example, the a40 amp that I recently completed was available from the PassDIY site as a downloadable PDF file containing everything that you need to know to build one 40wpc stereo amplifier. No such single document exists for this amplifier (except for this web page). There are several versions of it in existence that range from 40w to 100w versions of the amp, each with different power supply rail voltages, different bias points, different numbers of output mosfets, etc. As each of these designs works, there is no single "right" way to build the amp except for the way that best suits your needs. The original schematic (see below) runs on 15 volt rails, 4.5A bias, dissipates about 130w of heat per channel, and will deliver approximately 38 watts into both a 4 ohm and an 8 ohm load. The following references are good (and lengthy!) reading about this amplifier and its evolution.