A40 Part Substitutions — Nelson Pass / 2000

After 22 years, it appears that quite a few DIY enthusiasts are still eyeing the A40 Class A amplifier design, but are discovering that not a single transistor from this design is still available. The following information is for those scouting out substitute parts: The Lambda output devices are no longer available, and they weren’t that common to begin with. Lambda appears to still be in business, but not in the business of power transistors. Common everyday complementary power darlington transistors will substitute for these. They need to be rated at 75 watts or higher, 5 amps for higher, and… More...

Zen Variations 3 — Nelson Pass / 2002

In Part 2 we developed a new active current source for the Zen amplifier. In this part, we create a power supply regulator suitable for the Zen amplifier projects. Previous versions of the Zen amplifiers had no power supply regulation at all, or used capacitor/inductor/capacitor "pi" filters to smooth the ripple on the DC supply lines. In keeping with our philosophy of simple-aspossible, we want to develop a supply regulation system which gives us good regulation, with low AC noise and a stable DC value. The need for a good regulator is obvious enough. As simple as they are, the… More...