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.
MEASURES
-
Rails: +/- 17VDC under load
-
DC offset at speaker teminals: +/- 50mV cold, +/- 2mV hot
-
BIAS: 0.75A
-
Gain: 20dB
-
THD+N (at 1 Watt into 8 Ohms at 1kHz): 0.1%
-
THD (at 1 Watt into 8 Ohms at 1kHz): 0.08%
First Watt F5m
Designed by Nelson Pass. Minimalistic class A stereo power amplifier. 25W for 8 Ohm speakers.
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MEASURES
-
Rails: +/- 22VDC under load
-
DC offset at speaker terminals: about 5mV
-
BIAS: 1.1A
-
Gain: 16dB
-
THD+N (at 1 Watt into 8 Ohms at 1kHz): about 0.04%
NOTES
-
250VA transformer from Toroidy - 230V primary, 2x18V secondary
-
Dissipante 03/400B chassis from Hi-Fi 2000
LINKS
-
diyAudio forum: F5m kit, Build Guide,
-
diyAudio Store: F5M Core + PSU kit
-
Chassis: Hifi 2000
Last update: 16.05.2026.