"Fixing" noisy USB channel on Soundcraft Notepad-12FX

2026-01-21, Matěj Kafka (#audio, #hardware)

The Soundcraft Notepad line of audio mixers is pretty popular, with small size, lots of channels, a built-in USB audio interface and low-ish price. However, the audio interface started failing on my unit a few years after purchase, which is apparently pretty common, according to various online forums.

The first symptom was a slight imbalance between the two main channels, which I compensated using the balance knob. The second, much more annoying issue developed a few months later – the audio interface started emitting a constant hum, both into the USB channel and directly from the mixer (even with disconnected outputs, there was still an audible hum). Since I tend to listen on low volume, the noise was quite bothersome. Today, I decided to disassemble the mixer and see if I could fix the issue.

Short version: There's a daughter board on the back of the main PCB, which contains the audio inteface and FX circuit. You can easily disconnect this board, which gets rid of the noise and does not affect the analog functionality. Obviously, you'll lose the USB and FX, but the result is a fully-working analog mixer that no longer emits noise.

Disassembly

I did not find any disassembly videos, but the process is reasonably straightforward:

1. Remove two horizontal screws (fine-threaded) that hold in the plastic sides of the mixer.
2. Remove six screws (coarse-threaded) along the sides of the back panel. Now, the sides are only held by small plastic tabs, be careful not to snap them.
3. Remove six screws (fine-threaded) along the top and bottom of the back panel. Now, you should be able to remove it by slighly pushing the sides apart.
4. Unscrew the daughter board in the middle (small hex screws) and remove it.
5. Put the panel back on, reversing the process.