This retro-Electronics design (called Warp303) is inspired by the Proco RAT and Valve caster products; in fact, this build combines both circuits for an extra fat bass sound. I designed the circuit for the Cyclone TT-303 Bass Bot (the best TB-303 clone out there) and Korg Volca Bass. The Warp Factor toggle-switch switches between diode-types to alter the characteristics of the sound.
The idea of putting the Vacuum Valve on display is to bring out a Metropolis kind of feel - it's a cool show-off piece of work! :-)
Step 1: Diagram
Have a look at the diagram. The input feeds into the Distortion circuitry. The OPU7 (U1) and MPF102 (Q1) define the sound characteristics of the Distortion. You'll find plenty of discussions on the internet regarding the best type of components here (i.e. U1 & Q1) - but some of them are obsolete. I think the the component-types chosen here are a good choice.You can experiment with D1/D2 & D3/D4 as it will alter the sound of the Distortion.
The output of the Distortion circuit sits at R14 and R15. This is where the signal feeds into the Overdrive circuitry, starting at C14. Here we selected the ECC82 Vacuum Tube. You can replace it for the more difficult to find 12AU7 (some folks claim it sounds better - but the ECC82 is the European equivalent tube).
The end-signal arrives at '2/3' of P4 where it feeds into the relay.
The Output itself is either a direct copy of the input (i.e. by-pass) or, when switched, is the Distorted/Over-driven signal.
The 12V DC power supply feeding the Warp303 should be able to supply around 160mA.
Step 2: Components
As pointed out previously, U1, Q1 and the Vacuum Tube define the characteristics of the sound. You can browse the internet the find the more obsolete components in order to perhaps sound more analog - though, it will still sound awesome with the more available components as per the components list.
The Tube Guard is not an everyday item (not even on eBay) - Google 'Vacuum Tube Guard' to find the one you like best (Chrome or Copper if you want the design to look more Steampunk).
The illuminated toggle switch can easily be replaced for a typical stomp box foot switch - it just looks so much more cool using a launch switch.
The Orange LED2 in the diagram shines through the hole in the middle of the Vacuum Tube Base Socket. It's a feature making the glass tube light up - it will work just as well without. Here we picked Orange/Amber, but Blue is cool also.
The front design is based on the circuitry being put inside a purple stomp box, but there are many color-choices for you to pick from.
I am listing the actual Power Supply I used -- any other 12V DC (200mA) will do - although the cheaper ones can cause the circuit to hum.
Step 3: Front Panel
The front panel design is meant to be printed on an purple A4 size label.
In the pictures you can see the process; 1st print the front panel on plain paper. Cut out front and back and put these in place on the box with some cello tape. Use a sharp pointed object to punch pilot holes. 2nd, drill the holes. Makes sure all components fit nicely.
Once you are happy with the holes, print out the design on a purple A4 label. Make sure to clear grease from the box before putting the labels on. It's precise work here to align the holes. Once this is done, use a sharp knife to cut out the holes. You are ready to put in switches, potentiometer, LED and input/output jack sockets.
Step 4: Strip Board
Once all chassis components have been mounted, it's time to build the circuit (strip) board and wire everything up.
Have a look at the PCB .pdf; start with cutting the right size piece of strip board (11 strips by 45 holes). Go to the last page of the PCB .pdf and cut the tracks as per picture. Use Top View and Top View (X-Ray) to place/solder all components. A good start are the jumper wires, then resistors etc.
When all components are in place, use the connectivity diagram on the first page of the PCB .pdf to wire up the chassis components.
The Blue LED lights up as soon as power is connected.
Enjoy the fat bass!