MEASURES
-
Rails: +/- 24VDC under load
-
DC offset at speaker teminals: +/- 2mV
-
BIAS: 1.3A (0.61V on R13/R14)
-
Voltage gain: 10 (20dB)
-
THD+N (at 1 Watt into 8 Ohms at 1kHz): 0.08%
-
THD (at 1 Watt into 8 Ohms at 1kHz): 0.04%
MEASURES
-
Rails: +/- 24VDC under load
-
DC offset at speaker teminals: +/- 2mV
-
BIAS: 1.3A (0.61V on R13/R14)
-
Voltage gain: 10 (20dB)
-
THD+N (at 1 Watt into 8 Ohms at 1kHz): 0.08%
-
THD (at 1 Watt into 8 Ohms at 1kHz): 0.04%
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NOTES
-
R7 changed to 52.3k to remove excess negative DC offset at the output of the amp
-
R4 changed to 8.2 Ohms and 220uF bipolar capacitor added to remove DC offset at Edcor input (pin 1)
-
Boards, Edcor transformers and MOSFETs from TeaBag
-
Harris IRFP9240 MOSFETs
-
Matched Toshiba JFETs from FET Audio
-
Dual mono implementation
-
2 x 250VA transformers from Toroidy - 230V primary, 2x18V secondary
-
8 x 22000uF KEMET PEH200 in power supply
-
Deluxe 4U chassis from Hi-Fi 2000
RESOURCES
-
Manual: First Watt M2
-
diyAudio: Official M2 schematic, M2 Clone boards with 120mm UMS spacing
-
Other: Edcor
Last update: 10.03.2019.
NOTES
-
R7 changed to 52.3k to remove excess negative DC offset at the output of the amp
-
R4 changed to 8.2 Ohms and 220uF bipolar capacitor added to remove DC offset at Edcor input (pin 1)
-
Boards, Edcor transformers and MOSFETs from TeaBag
-
Harris IRFP9240 MOSFETs
-
Matched Toshiba JFETs from FET Audio
-
Dual mono implementation
-
2 x 250VA transformers from Toroidy - 230V primary, 2x18V secondary
-
8 x 22000uF KEMET PEH200 in power supply
-
Deluxe 4U chassis from Hi-Fi 2000
RESOURCES
-
Manual: First Watt M2
-
diyAudio: Official M2 schematic, M2 Clone boards with 120mm UMS spacing
-
Other: Edcor
Last update: 10.03.2019.
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.
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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: 11.06.2023.