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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.

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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%

RESOURCES

Last update: 11.06.2023.

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