Preamp schematic and PCB layout

by mikaelivarsson

As I wrote in the first post about the double bass preamp I based my design on Francis Decks “Bare Bones Bass Blender”. The schematic for it can be found here: http://personalpages.tds.net/~fdeck/bass/bbbb.jpg

I used KiCad to design the schematic and PCB layout. KiCad is a free and open source software suite for EDA (Electronics Design Automation). I have previously used Eagle PCB, but now since I’m more or less using Linux only, and due to the fact that the free version of Eagle has some restrictions I decided to try KiCad. The preamp was my first complete project using KiCad and so far I am very pleased with it.

Here is the schematic for my preamp:

bass_preamp_sch

(pdf: bass_preamp)

The schematic is pretty much straight forward, with the two inputs on the top left. In the bottom left is the circuit that supplies the-op amps with +/-4.5V derived from the 9V input (which could be a 9V battery but in my case it will be a regulated 9V “wall adapter”) and the bottom right is the output. I will mount the switches, jacks and potentiometers on the case, which is a more robust design compared to mounting the electromechanical parts directly on the PCB, and therefore it is a lot of connectors on the schematic were wires will be soldered connecting to the external components. I will probably end up using a Hammond 1590B stompbox enclosure for the casing, depending on how crowded it will be due to the fact that the design use 5 potentiometers.

This is how the layout ended up:

bass_preamp_crop

(One of the neat features of KiCad is the possibility to view your layout in 3D.) It’s a 2 layer design and I’m using mostly surface mount components.

That’s it for now. I will update again when the PCBs and components arrives.