Making a Simple Eurorack Mixer
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Apr 21, 2022
- edited: May 30, 2025
In this video I design and build a simple eurorack mixer module with a low parts count.
Video #
Correction #
The 100:6.25 ratio I mentioned in the video at 4:50 is bogus because I calculated it based on only one datapoint at 50% of the pot rotation. If you want a linear audio volume curve you can use my tool at https://tools.sandelinos.me/gain-playground/ to experiment with different resistor values to get a response you like.
Updates #
I have made updates to the circuit and stripboard layout since releasing the video. The schematic and layout below are for version 1.1. You can find version 1.0 at the bottom of the page. The list of improvements made in 1.1 is as follows:
- Dropped R6 & R7 from 100k to 10k because lower impedance equals less noise.
- Added capacitors in the feedback paths of the opamps to improve stability and filter out supersonic noise.
- Made 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. 100 Ω is enough for this and having a low output impedance is beneficial for a variety of reasons.
- Added filtering for the power input.
Schematic #
Download:
Stripboard layout #
Download: repository/Simple-Mixer.diy (0.0 MiB)
BOM #
| Part | Value |
|---|---|
| R1, R2, R3, R4, R5 | 100k |
| R6, R7 | 10k |
| R8 | 100 |
| R9, R10 | 22 |
| C1, C2 | 100n |
| C3, C4 | 10u |
| C5 | 47p |
| C6 | 470p |
| U1 | TL072 |
Panel #
Here’s the template I used to make the panel:
Other people’s builds #
In this section I share pictures of other people’s builds of my circuits. If you want to show off your build here, contact me.
Jurre #
Built in May 2026 by Jurre (@bakju_h on Discord). He designed a PCB panel for it with a nice graphic resulting in a very professional looking module. At the time of writing it is the only build of version 1.1 in the world, so thanks to Jurre for verifying the stripboard layout.
Version 1.0 #
Schematic #
Stripboard layout #
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.