Found some more info... (BD-Design)

by Cappy , Wednesday, November 28, 2007, 18:34 (5993 days ago) @ Bert
edited by unknown, Wednesday, November 28, 2007, 19:51

Bert,

I believe that Pass's current source amps were called the "F1" and "F2". The F3 and F4 are more amenable to other speaker types.

From 6moons:

The F1 was a transconductance or current-source amp primarily intended for crossover-less single-driver speakers. The F2 was another current-source amp but single-ended. The F3 uses a special JFET as output device but only makes 10wpc. The F4 looks at the über-gain scenario today where hi-output sources plus high-gain preamps mean that many amps, into many speakers, run well below unity gain most of the time. The F4 asks a good question. What'll happen if such redundant amplifier gain was essentially eliminated?

So as I understand it, the F4 is a voltage source amp, you just need to get the voltage somewhere else. :wink:

Basically it is a sophisticated buffer.

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