Making a Simple Eurorack Mixer
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Apr 21, 2022
- edited: May 07, 2025
In this video I design and build a simple eurorack mixer module with a low parts count.
Video
Schematic
Download:
Stripboard layout
Download: repository/Simple-Mixer.diy (0.0 MiB)
BOM
| Part | Value |
|---|---|
| R1, R2, R3, R4, R5, R6, R7 | 100k |
| RV1, RV2, RV3, RV4 | B100k |
| R8 | 1k |
| C1 | 100n |
| U1 | TL072* |
* You can use pretty much any dual op-amp you want here.
Panel
Here’s the template I used to make the panel:
Update (2025-05-07)
The 100:6.25 ratio I mentioned in the video at 4:50 is bogus because I calculated it only based on one datapoint at 50% of the pot rotation. Actually a ratio of 100:14 would be closer overall over the whole range of the potentiometer.
Also here are some recommended changes that I would make if I were to build this module again today:
- Replace R6 & R7 with 10k because lower impedance equals less noise.
- Add a 47pF capacitor in parallel with R5 to filter out supersonic noise.
- Add a 470pF capacitor in parallel with R7 to filter out supersonic noise.
- Make R8 smaller. TL072 has short-circuit protection built-in already, so actually the job of the resistor is just to prevent the opamp from oscillating when driving capacitive loads like long cables. 47-100 Ω should be enough for this and having a low output impedance is beneficial for a variety of reasons.