Shared Projects by theepicureanshoppe

You can use this little board to adapt a Bourns 3296W (or Vishay T93YA) trimpot as a bias adjustment control in a tube amplifier. The bias supply from the amp goes to “B.IN” pad, bias supply out comes from the “B.OUT” pad, and the “G” pad goes to the main bias resistor to ground depending on the circuit. The resistor in parallel is an emergency pull-down resistor. I took this idea from the Valve Wizard. They write: “This ensures that if the pot wiper fails to make good contact with the rack (because it is dirty or worn out, say) the grid leaks will effectively be connected directly to the raw bias supply through R1 instead, biasing the valves safely cold. R1 should have a value of about ten times [the trim pot] so it has negligible effect on the rest of the design.”

Schematics, EAGLE and Gerber files, and other references here: https://drive.google.com/drive/folders/1CyXvsXiN4TgLzc1Nf8XQB_ZOHwcMmx7g?usp=sharing

Pretty much pulled from the datasheet and inspired by the circuitbenders.co.uk board.

BILL OF MATERIALS: - R1: 3 kOhm 1% Metal Film - C1: 0.1 uF 50v MLCC (C0G/NP0 or X7R) - I/O pads: either just wire or Phoenix 1729131 for terminals - Trim pot: Bourns 3296W-1-223LF (22 kOhm, 25k will work) - LTC1799 module - pads “2” and “3” go to a panel mount pot. You can use C100K or C500K for wider range of adjustment. I used this in an ART Multiverb and actually preferred the taper of audio/logarithmic pots over the reverse-log. If using the audio/log pot, run the wire from the pin 3 pad to pin 1 of the pot.

Here is a Mouser cart with all of the parts: https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=683c34a120

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/LTC1799.pdf Circuitbenders version: https://www.circuitbenders.co.uk/forsale/LTC/LTCPCB.html

www.zachweeks.com/pedals

See bottom of PCB for part numbers. Use the male terminal for speaker wire or just solder wire directly to the big pads behind the pins for the terminals.

For a 4x12, I recommend wiring each pair of speakers in parallel and then running the positive and negative leads to S#+ / S#- respectively. For example, two 16 ohm speakers in parallel = total impedance of 8 ohms. Running two 8 ohm pairs (or alternatively, just two 8 ohm speakers in a 2x12) gives you the option of 4 ohms with the Parallel jack or 16 ohms with the Series jack.