Yes, it is high.
Here is a link from FirstWatt on the F1:
www.firstwatt.com/f1.html
"It has both balanced and single-ended inputs. The input impedance is nominally 80 Kohm, and the output impedance is 80 ohms."
And from the F1 manual:
www.firstwatt.com/pdf/prod_f1_man.pdf
"Input Impedance, unbalanced 50 Kohms, 8 ohm load
Here is a link from FirstWatt on the F1:
www.firstwatt.com/f1.html
"It has both balanced and single-ended inputs. The input impedance is nominally 80 Kohm, and the output impedance is 80 ohms."
And from the F1 manual:
www.firstwatt.com/pdf/prod_f1_man.pdf
"Input Impedance, unbalanced 50 Kohms, 8 ohm load
Output impedance 80 ohms"
In his 2004 review of the F-1, Dick Olsher wrote:
"Current drive offers a major alternative to the speaker-amplifier interface. A transconductance amplifier is operated as a current source with a high source impedance relative to that of the speaker. The output impedance must also be linear and frequency independent. An ideal current source would possess an output impedance so large as to be considered infinite relative to that of the speaker. The F1's 80-ohm impedance is certainly adequate in this regard."