Especially if you count in the additional power just to run the heater filaments on a tubes version, which is about 5.5 W for 1x EL84 and 1x 12AX7. Anyways switching DC supply bricks are pretty cheap and readily available to run a Class A at 5 to 10 W. The preamp will draw maybe an added 100 mA, negligible. I think Nelson Brock is offering the ACA MinMax PCB (bare) at around $10 (USD) for a set of two boards. I don't have any experience with the ACA Mini, and not personally involved in any way with that project. I imagine the JLH would be similar in performance though?
Incredibly they used a single 2N3055 driving a very common EI transformer.
Obviously on purpose, they must be after some quirk or non linearity they like.
They are still using it today, so it' s by choice, not by "need".
Some early design stage work I was doing on Class A Jfet push pull preamp stage driving an audio transformer. I have since gone to a less expensive open frame style audio transfo, which performs very well especially considering it's about 1/10 the price. The final version has a high impedance (1M) buffer input, variable gain 0 to about +23 dB (local NFB) and balanced transformer isolated output. To do a full on guitar preamp, I am planning on putting an additional gain stage at the input, either a passive or active tone section after that..haven't decided which. Cheers!
