[quote author="drpat"]I wonder if the 2N5566 units were a mod to the stock one??? Seems as if the numbers would have been sanded off if it were stock.[/quote]
I'm almost sure it was stock because I remember I read an interview with GML where he mentions this part (2N5566).
(later)
While writing this I did some searching and found the GML interview:
"After I moved to Los Angeles in 1975 I redesigned the basic discrete op-amp. For all of the GML and Sontec designs (Burgess and I, among others, own the company jointly, though you'd never know it) I designed two significant revisions. The first had truly stupendous HF response; it featured a 2N5566 dual J-FET running at an ungodly high current, and a highly-linear second stage which featured the dominant pole. It was ridiculously fast (150mHz gain-bandwidth, 600v/us slew rate) and stable (no instability over a 60dB gain-variation range) as it was unreliable (from smoking to out-and-out explosions). We've long since gone to a fast, very-high-gain NPN input stage, keeping the high-voltage gain 2nd stage for GML designs, although the design evolves as semiconductor manufacturers obsolete discrete parts."
chrissugar
