Aleph J Clone

Designed by Nelson Pass. 2-stage topology with input stage using high quality matched JFETs and output MOSFETs operating in single-ended Class A mode. 25W (for 8 Ohm speakers), 13W (for 4 Ohm speakers). 240 kOhm input, 0.4 Ohm output impedance. More details on First Watt website.

Front Panel
Back Panel
Front Panel
Main Boards
Main Boards
MOSFETs
Heatsinks
VU Meters
VU Meters Driver Board
Back panel
Inside
Inside
Inside

Latest changes/improvements:

  • Transformer changed from Avel Lindberg to Toroidy (a bit more quiet)

  • KBPC3510 rectifier bridges replaced with fast/soft recovery ones with CRC snubber

  • R1-R4 resistors matched within 0.1%

NOTES

  • 4U Deluxe chassis (Hi-Fi 2000) with 2 extra holes on back panel for XLR sockets

  • All boards from diyAudio Store

  • Matched MOSFETs from Hannes

  • Matched JFETs from FET Audio

  • Shielded toroidal transformer from Toroidy - 500VA, 2x115V primary, 2x18V secondary

  • 8 x 22000uF in PSU

  • SIFAM AL20SQ Audio Level Meters from CANFORD

  • VU Meter Driver Kit from JLM Audio

  • 12V Linear Power Supply Kit from Conrad Electronic

  • PSU and more chassis photos - see my First Watt F4 clone

MEASURES

  • Rails: +/- 21.5 VDC (under load)

  • DC Offset: < 1 mV (< 20 mV cold)

  • Gain (at 1 kHz): 9.5 (19.6 dB)

  • THD+N (at 1 Watt into 8 Ohms at 1 kHz): 0.07%

  • THD (at 1 Watt into 8 Ohms at 1 kHz): 0.04%

Last update: 14.09.2016.

© 2021 by Prog Solutions Ltd. All rights reserved.

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