The last transistor active preamp I owned was Nelson Pass’ Threshold SL 10. It was a pure class A design that used cascade gain stages that with matched FETs driving a PNP, whose collector was biased by a constant current source that drove a complementary pair of followers. It also had an outboard power supply. The moving coil input is still quite innovated by today’s standard and was exceptionally good. It cost a staggering $950 in 1979 but compared to my clunky looking Audio Research SP-3( with some number behind it, I can’t remember what the last version was) the SL 10 was simply beautiful, sleek, thin and had the most beautifully shaped knobs I have ever seen to this day. It also had a built-in moving coil head amp that the audio press said was the very best there was. I drooled over it for several years and eventually sold my SP-3 in the early 80s and purchased my own Threshold SL 10 which pleased me for many years.
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