The B-17B preamp prototype is finally complete! Here is a picture of the unit working with both Gain and Master controls set close to 0dB output.
The output buffer and VU meter driver circuit was added on a daughter board as you can see in the side view picture below.
So now everything is ready for some musician testing in the South Lab. Unfortunately this will probably wait until Memorial Day weekend when the prototype can be hand-delivered. After that testing the next step will be to order printed circuit boards to ensure the final model is rugged enough for musician use.
With some work I was able to fit the components onto a board layout within the size limits of the Cadsoft Eagle freeware version. Here is a picture of the layout.
The tube socket for the 12AX7 will be mounted on the backside of the board to allow the tube to be visible outside the case of the unit. The components external to the board will be the AC inlet fuse, AC filter cap, power switch, pilot lamp, the power transformer, the input and output jacks,the two VU meters, and the five potentiometers.
Meanwhile it is time to take a pause in development while the North Lab is being relocated. The new lab will be a significant upgrade over the bare concrete floors and dark spaces of the current lab. Definitely not-so-evil!