Power Amp Design

A veritable smorgasbord of historical articles is maintanted and still being extended by Douglas Self. Especially his Wireless World section of articles is priceless, but in general his site has lots of interesting info.

Audio design leaps forward? Giovanni Stochino, EW&WW, Oct 1994.

Amplifier design for low Transient Intermodulation Distortion - Matti Otala's Low Tim Amplifier from AES preprint H-6(R) from Feb 1973. This was actually a joint design effort with Dutch designer Jan Lohstroh - read my interview with Jan Lohstroh for more insight. This is the original AES preprint for the 'Otala-Lohstroh' low-tim amplifier design (AES preprint H-6(R), AES convention 1973, Rotterdam, The Netherlands).

Several vintage documents on thermal distortion in power stages, resulting from signal-related die temperature changes. Also called 'memory distortion': 'La distorsion thermique' Part I, Part II, by Héphaütos (from L'Audiophile, 1984), and 'Amplifier transient crossover distortion resulting from temperature change of output power transistors', AES preprint 1896 (October 1982). This is a subject that has intrigued me for many years and in 2014 I did some experiments to find out if there was anything to it. My conclusion: memory distortion (from thermal transients) does existst but is very unlikely to be audible. You can read my report in Linear Audio Volume 9.

"Class B in a new class" by Mike Renardson, Electronics World April 1998. One of several designs that have been promoted over the years to improve class (A)B designs by, in this case, ensuring that none of the output stage halves ever turn off, thereby greatly decreasing crossover distortion.

A classical amplifier in the mid-70-ies was the 'Barney amplifier'. Designed by Barney Oliver at HP, and manufactured, tested and documented as a regular HP piece of equipment. The Tech- & User Manual is here. A gem!