AL20 - Class-A Baby Leach Amp Design


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AL20 is a pure class-A "Baby" Leach solid-state power amp.

  • 20W pure class-A
  • complementary symmetry throughout
  • unique direct-monitoring bias circuit
  • no warm-up time required
  • all-modern BJTs
  • on-board heat sink for drivers
  • operates at +/-24V
  • board size 3.2x3.5" 81x89mm

AL20 uses a unique bias circuit that monitors the output current and locks its value. There is no waiting for things to warm up - you get beautiful low-distortion class-A sound right from power-up!

A generous heat sink is required for this project.

The free version of this info package, AL20 FREE (400 KB), includes enough info for a home hobbyist to make his own printed circuit board, and includes the following PDFs:

  • schematic
  • parts overlay
  • top foil
  • bottom foil
  • bill of materials

Click HERE to download AL20 FREE.

AL20 COMPLETE (1,945 KB) includes all of the above info, plus a 15-page PDF covering how it works, wiring, component substitution, and use in home theatre systems. AL20 COMPLETE also includes the Gerber and Excellon files for professional PCB manufacture.

AL20 COMPLETE includes:

  • schematic
  • parts overlay
  • top foil
  • bottom foil
  • comprehensive notes - 15 pages
  • Gerber and Excellon files
  • PSU details
  • safety notes

 Click "Add to Cart" above to purchase the AL20 COMPLETE design.

About London Power

London Power was founded in 1990 by Kevin O'Connor, after two decades of research into innovative audio amplification techniques. Kevin is an audio designer, author and speaker, known for his proprietary methodology called Power Scaling, and for his eleven books on audio subjects. Whether you seek amps, kits or information, you'll find useful answers here on not just the "how" but the "why" of audio amplifier design. Please enjoy the information on this site, and don't hesitate to contact us with questions.

Contact Us

(807) 473-0952
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PO Box 10012, Thunder Bay, ON P7B 6T6 CANADA