SY said:Why not split the difference and use a cascode input stage, jFET on the bottom, tube on the top? I use an NTE458/E88CC combo, but the Toshiba 2SK147 is a popular choice. Very, very quiet.
SY,
Do you have the actual schematic?
I saw one from 'borbelyaudio' published in Costruire Hi-Fi some times
ago.
I built that preamp back in the early 1980s, so the schematic doesn't exist in digital form. I'll see if I can sketch something up. Basically, it's single-ended, the tube has a 180V rail, 45k plate resistor, a 6.9V reference sent to the grid, no resistor between the cathode and the FET drain, and a small source resistor (100 ohm). FETs were selected in-circuit (a lot of tedious plugging in and out).
AW's use of the FET/tube in CC differential is a better approach, I think.
AW's use of the FET/tube in CC differential is a better approach, I think.
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