Pass Labs First Watt F7 Power Amplifier

Pass Labs First Watt F7 Power Amplifier


The F7 is a very unique power amplifier, a two-stage push-pull JFET/MOSFET topology with fewer parts than any First Watt amplifier to date and incorporating a very interesting balance of very low negative voltage feedback and a little bit of positive current feedback to give an astonishing measure of control over reactive loudspeaker loads.


Measured at 120 V AC and an 8 ohm load:

Distortion @ 1 watt 0.05%
Input Impedance 10 Kohm
Gain 14.5 dB
Input Sensitivity (1 watt) 0.53 V
Input Sensitivity (max output) 2.7 V
Damping Factor >100
Output power 8 ohms 20 watts @ 2% THD, 1KHz
Output power 4 ohms 30 watts @ 3% THD, 1KHz
Class A envelope 40 watts peak @ 4 ohms
Frequency response DC to -3 dB @ 100 KHz
Noise 100 uV unweighted, 20-20 KHz
Power consumption 170 watts
Fuse 3AG slow blow type - 2.5 Amp for 120VAC, 1.25 Amp for 240 VAC