Starting to make some real moves on this next amp. All of the parts for the prototype are ordered (I think...hard to keep track). Have a massive shipment coming from Mouser tomorrow. Usually the little passive components represent a somewhat negligible expense compared to the other parts - not the case this time around. Lots of sand assistance in this build, so lots passive components.
For the prototype, I got these cool socket boards from Hificollective.
And everything will be built on the 2'x2' piece of plywood below, doing both channels.
This amp will have four different power supplies, Antek transformers, although I haven't ruled out switching to something else for the big guy in the middle for space saving measures since I am only using one of the two secondary windings. The 841 B+ (via voltage doubler), 801A B+, and source follower V+ will be Maida regulated; the source follower V- / bias supply will be shunt regulated.
Rod Coleman regulators for both input and output tubes, filament bias for the 841, fixed bias for the 801A. I was originally looking at getting some cool meters for the 801A fixed bias, but I am starting to consider using test points and current sense resistors instead for a few different reasons, one of them being space. That is TBD, but will be the approach for the prototype.
The circuit I am using for the 801A bias as well as the constant current sink for the source follower will need to be prototyped - I have some solderable prototyping PCBs coming to build them out. Once everything is up and running, I will put together the gerber files and order the finalized PCBs.
Yet another thing coming to me - a giant 12" x 7" x 3" heat sink. Has something like a 0.25 C/W thermal resistance with zero airflow, going to throw all of the regulators on that bad boy for the prototype, will use it for future prototyping as well.
By the time I get this all laid out and the power supply and input stages working appropriately, the output transformers should be here.
So yeah, this is the big project right now, a monster of a 801A A2 SET amplifier, ~6-7W output into 8ohms.