First Watt F4 Clone
Designed by Nelson Pass. Class A push-pull power amplifier with no feedback and no voltage gain, only current gain. 25W (for 8 Ohm speakers), 40W (for 4 Ohm speakers). 47 kOhm input, 0.2 Ohm output impedance. More details on First Watt website.
![]() | ![]() | ![]() |
---|---|---|
![]() | ![]() | ![]() |
![]() | ![]() | ![]() |
![]() | ![]() | ![]() |
![]() | ![]() | ![]() |
![]() | ![]() | ![]() |
![]() | ![]() | ![]() |
![]() | ![]() | ![]() |
![]() | ![]() | ![]() |
NOTES
-
4U Deluxe chassis (Hi-Fi 2000) with an extra hole on back panel for XLR socket
-
All boards from diyAudio Store
-
Matched MOSFETs from Hannes
-
Matched JFETs from FET Audio
-
500VA transformers custom made by Avel Lindberg 2002 - 2x115V primary, 2x18V secondary
-
8 x 22000uF in PSU
-
R1 changed to 100k 0.1% in preparation for ImPasse
MEASURES
-
Rails: +/- 25 VDC
-
DC Offset: < 1 mV (< 30 mV cold)
-
R3/R4: 60mV
SCHEMATICS

RESOURCES
-
Service Manual: First Watt F4
-
diyAudio: F4 power amplifier, F4 guide, Store
Last update: 28.09.2014.