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
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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
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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 B1 preamp with Korg Triode
Designed by Nelson Pass. B1 pre-amplifier which uses Korg Nutube to generate 2nd harmonic distortion. More details on First Watt website.
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SETTINGS & MEASURES
-
T1: 24VDC
-
T4: 9 VDC
-
T5 / T6: 0.65 VDC
-
T7 / T8: 9.5 VDC
NOTES
-
Linear power supply in a separate chassis
-
LM317 regulator
-
Galaxy 2U chassis from Hi-Fi 2000
-
Matched Toshiba 2SK370 JFETs (Idss 5.1mA) and Korg Nutube DIY Preamp board - Christmas gift from Nelson, thank you.
-
Ladder type 25k stepped attenuator based on Seiden 4 pole 23 way switch and Nickel-Chromium thin film resistors 1/4W 0.1%
-
ELMA 4 pole 6 way input selector switch
-
See also BA-3 Front End page
RESOURCES
-
Manual: pdf
-
diyAudio: B1 with Korg Triode
-
Other: Preamp Muting Circuit
Last update: 11.06.2023.