Alembic F-2B preamp | moosapotamus May 06, 2012The high voltage (shown as 314V on the PSU schematic) connects to B+ on the preamp schematic. The low voltage (shown as 5.6, 6.3 or 12V on the PSU schematic) connects to the vacuum tube pins 4 & 5. That is not shown on the preamp schematic, but you can see it in the PCB layout. Finally, all the ground points are connected together. That’s it! Alembic F2b preamp – FrogPedals Class A vacuum Tube preamp based on the Fender Dual Showman preamplifier section which inspired the Alembic F2b preamp. It is high quality 1 board with 2 ounce copper traces (double the normal printed circuit boards) with Gold plated solder pads.