Pass Aleph 30 and 60

LIGUY

You are very knowledgeable on this stuff, so perhaps you can answer my question:

Just about every SINGLE-ENDED amp on the planet - including most of the FIRST WATT models - drop power into lower impedances.

This was very true of my 30w FIRST WATT J2, which was down to 12w into 4 Ohms.  This is the reason I eventually sold the gorgeous J2.

So how is it that the little ALEPH 30 can produce 30w into 8 Ohms and 40w into 4 Ohms?

What gives?

Sondeknz

I believe the answer to your question about power into speaker impedance is in circuit topology. Voltage gain stages vs. current gain stages. I don’t have simple details at hand since this information comes from reading lots of articles over the years.
Interviews with Nelson Pass about his circuits are plentiful on the Web and Mr. Pass speaks about things in a fairly straight forward and easy to understand way. I find them both interesting and informative. You may, as well.

The answer is that the J2 is a single ended amp with a single JFET output being operated in common source mode from an active current source. That mode of operation gives you both current and voltage gain. Driving a lower impedance causes a drop in the voltage because there's a rise in current output. It's an amp particularly sensitive to how the speaker loads the output devices.