Interresting Class A preamp with current regulators

Well 10V is a lot of headroom to lose, and the noise specs are completely missing, and there's no real indication of bandwidth, the quality of the voltage reference or the shunt resistor. That article is about creating a market for this product primarily, not high performance amplification.


There are several errors in circuit 15 too, so I'd be skeptical about whether any of these have even been built and tested.

Might be interesting to experiment with these things, finding out how good they are given the datasheet is pretty slim.
 
Yes, fig 15 is at least missing intersection dots. I've built simple single ended circuits with resistors in the anode, cathode and gate with good results but didn't have the cleanest power supply. Their as easy to use as triodes in that topology. With minimal resistors a builder can bolt them to an isolated heatsink and wire up with binding posts.

Some thing to think about.
 
Also in fig 15 the 150 ohm resistor doesn't match the purported gain of 55, whereas 180 does. The DC feedback/bias network makes no sense (*), there's likely another missing intersection dot and wrong resistor values.


(*) It may be something to do with powering the "opamp" builtin to the circuit, which is not fully explained.