I received the final prototype boards on Monday, and assembled the first one using parts from the test BOM (Bill-Of-Materials) order. The purpose of doing this is to make sure the Bill-Of-Materials and the board are correctly specified, so that when I send the order to manufacturing, I can expect it to work.
It didn’t work at first, which was cause for concern, but it turned out that one of the PNP transistors was no good. Once I had replaced it, everything worked perfectly.
Once the Tempco resistors have arrived (mid-August), I will build the rest of the boards, and send them off to my test subjects.
Triangulum Research 
er. Almost perfectly. Working out issue with waveshapes at low frequencies. Haven’t yet figured out if it’s an artifact of component variations, or board layout. Working on it…