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.

Front view
Front view
Back view
Main boards
Main boards
Main board
Main board
MOSFETs
Heatsink
Heatsink
Heatsinks
Power Supply board
Power Supply board
Power Supply board
Power Supply board
Power Supply boards
Chassis
Chassis
Transformer
Chassis
Chassis
Power Supply
Power Supply
Chassis
Chassis
Chassis
Chassis

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

Last update: 28.09.2014.

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