Notes:
- If A10K (“audio” or log) pots aren’t handy, there’s a 2K logarizing™ resistor between the wiper and ground which will let you use a B10K linear pot instead. If you’re using A10K pots then jumper the 2K pads with a blob of solder or 0K resistor.
- The 1N4007s in the schematic and silkscreen are called “M7” when using SMD packages.
- The through-hole 100uFs are unnecessary.
- The 10K resistor on the output is unused.
- Change the 15K Output Level resistor to 2K to lower output to line-levels.
- Replace the Decoupling Capacitors with jumpers or 0 ohm resistors to mix DC (control voltage) signals.
Schematic:
BOM:
Qty | Value | Device | Package | Parts | Description | Source 1 | Source 2 |
|---|---|---|---|---|---|---|---|
| 4 | 100n | CAPACITOR | C0805K | C5, C6 | |||
| 4 | 1uF | CAPACITOR | C0805K | C1, C2, C3, C4 | |||
| 3 | 10uF | CAPACITOR | C0805K | C10, C11, C13 | |||
| 2 | 100uF | CAPACITOR | E2,5-7 | C7, C14 | POLARIZED CAPACITOR | ||
| 2 | 100R | RESISTOR | R0805W | R7, R9 | |||
| 5 | 2K | RESISTOR | R0805W | R11, R12, R13, R14, R15 | |||
| 7 | 10K | RESISTOR | R0805W | R1, R2, R3, R4, R5, R8, R10 | |||
| 1 | 15K | RESISTOR | R0805W | R6 | |||
| 2 | 1n4007 (M7) | DIODE | SOD323-W | D1, D2 | M7 is the SMD version of the 1n4007 | ||
| 5 | A10K | POTENTIOMETER | 9MM SNAP-IN VERTICAL | POT1, POT2, POT3, POT4, POT5 | 9mm vertical snap-in pot, Alpha / Panasonic style with 6mm built-in knob. | ||
| 1 | TL072 | OPAMP-DUALU | SO08 | IC1 | TL072 or equivalent | ||
| 5 | 3.5mm Jack | THONKICONN | IN1, IN2, IN3, IN4, OUT | 3.5mm socket for Eurorack modular synths | http://shop.erthenvar.com/collections/accessories/products/3-5mm-inline-jacks | https://www.thonk.co.uk/shop/3-5mm-jacks/ | |
| 1 | Power Lead | "Futaba J" Tile power lead | http://pulplogic.com/product/tile-tail/ |
Build Instructions:
Separate panels carefully by gently flexing and twisting back and forth, ensuring that they break cleanly at the “mouse bites”. File the leftover tabs down until flush with the edge of the panel or PCB.
Clean the PCB with isopropyl alcohol.
Add all of the surface mount parts by your preferred method.
- If using A10K pots replace the 2K resistors circled on the PCB with 0-ohm resistors, or solder jumpers.
- Don’t install the large electrolytic caps, or final 10K resistor shown on diagram above.
- Replace the Decoupling Capacitors with jumpers or 0 ohm resistors to mix DC (control voltage) signals.
Double-check soldering for shorts, especially at the legs of the opamp.
Install the pots. Ensure they are flush before soldering pins. Don’t solder the snaps until the very end when you’re sure everything is working.
Add the power lead.
Install the jacks. I found this procedure works well:
- Solder the center jack (#3), careful to ensure it’s centered and flush.
- Add the rest of the jacks, then attach the front panel with a nut on jack #3, holding everything in place.
- Turn module over and solder the remaining jacks.
Check the soldering for shorts.
Power the module and check for +12 and -12 at the opamp (see picture above).
Using an audio source and speaker or oscilloscope, check that all inputs and output are working.
Solder the pot snaps to the PCB.
Clean the flux from the PCB.
Attach and secure the panel if not done already.
Done!