Amp from Nelson Pass: The First Watt F7
elson Pass's most recent amplifier
design is the First Watt F7 ($3000), a 25Wpc stereo model with fewer parts than any
previous First Watt amplifier. Its two-stage push-pull JFET input/MOSFET output topology
is an update of the earlier F5 amplifier. The F7 embodies many of Pass's core design
tenets, including very wide bandwidth, low distortion and noise, and a large class-A
operating region. The F7 uses no capacitors or transformers, apart from those in the power
supply, and it employs modest amounts of negative feedback in concert with a small amount
of positive current feedback to create an amplification circuit with an output impedance
approaching zero, so the F7 can handle a wider range of speaker loads. "Of course you
can achieve a similar effect with tons of negative feedback, but I think this is more
elegant and sounds better," explains Pass.
by The Audio Beat
| July 25, 2016
"This is a different amplifier," he further
explains. "The diversity of audio taste being what it is, not everyone will prefer
it. [But] I presume that a certain segment of audiophiles will like it."
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