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.

Main board
Main board


  • T1: 24VDC

  • T4: 9 VDC

  • T5 / T6: 0.65 VDC

  • T7 / T8: 9.5 VDC


  • 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


Last update: 12.02.2019.

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