Single stage class A calculations...

[bogdan_borko]

The design was actually for 4 ohms and used to drive a speaker from 70Hz up. Surprisingly, the bass is maybe the best subjective characteristic, very strong yet tight sounding.

The servo contols idle currnent, via an otherwise not very relevant dc output voltage (note that the drain of the output fet idles very near the supply rail, dc bias equals dc voltage across the inductor resistance).

So, yes, weird, but also one of my favorite amps. The other is its newer variation.

Yes you have limited LF bandwidth because 20mH choke, maybe avoiding problematic speaker impedance results good bass...just guessing.

Also, "triode characteristics" of input mosfet are not linear at all for 3.4V Vds. and so on... Do you have a thread for that amp I don`t want to hijack the thread? In the link i sent of my amp you can see I used common emitter CFP with gain to use less gain stages, but I had to use gnfb. Your follower output stage have a very low distortion but I think the input stage is a "sound signature"...

Anyway I`m very interested in low power solid state SE amps, and I`m experimenting with one right now...

 

[bogdan_borko]

Something that I just read in an interview with N. Pass here: Nelson Pass Interview - Audiophile Review

"In 1975 the Threshold 800A was a five-stage amplifier sporting a triple series / triple parallel / triple Darlington output stage and a dynamic bias circuit. By 1998 the Pass X1000 delivered a high quality kilowatt with only two stages. Currently I have a couple of amplifier projects with only one transistor."


Any idea what project he might be referring to here with 1 trans?

Some of the First Watt amps I guess.

 

[bwaslo]

Hi Bogdan, yes the thread was http://www.diyaudio.com/forums/solid-state/276375-single-ended-class-no-global-feedback-8w-mosfet-low-output-z.html

Distortion is rather low considering. Probably most due to high transconductance and source degeneration. With the resistor (that feeds current to the cascode collector) replaced with a current source it gets better still.

 

[famousmockingbird]

Something that I just read in an interview with N. Pass here: Nelson Pass Interview - Audiophile Review

"In 1975 the Threshold 800A was a five-stage amplifier sporting a triple series / triple parallel / triple Darlington output stage and a dynamic bias circuit. By 1998 the Pass X1000 delivered a high quality kilowatt with only two stages. Currently I have a couple of amplifier projects with only one transistor."


Any idea what project he might be referring to here with 1 trans?

Maybe the F2? I know he has been working on a push pull class A around the Static Induction Transistors. Maybe he is using the SIT's with the F2 circuit to get a more triode sound?