3D Printable Rear Case Cover for Raspberry Pi + Wolfson Card + PiHut case

I drafted a design for a new rear case cover for the Pi Hut case for the Raspberry Pi official 7″ touchscreen

The Wolfson Card I fitted here prevents fitting of the original rear case cover, so I drafted up a quick design in Tinkercad and a work colleague 3D printed it for me.

The design is shared on Tinkercad, so feel free to use and modify for your own use.

Posted in Engineering, Gadgets, Music, Streaming | 1 Comment

The Wolfson Sound Card Noise Gate and 24 bit Data

Recently I did some measurements on the Wolfson card to get an idea of the dynamic range. When playing a 24bit file @ -100dBfs there was no output from the card.

This was perplexing, as the noise floor is some 20-30dB below that.

I set about making an amplitude sweep test file, sweeping from -60dBfs to -144dBfs and then playing that back on the Wolfson. At -90dB the output would vanish!

Continue reading

Posted in Uncategorized | Leave a comment

Improving PSU filtering on the Wolfson Raspberry Pi Sound Card

I’ve been thinking about elegant ways to improve the PSU filtering of the Wolfson card and to ensure that any switching noise from the relatively noisy power supplies Raspberry Pi’s are usually used with is effectively¬†filtered.

There’s plenty of possible solutions here, involving various regulators or large capacitors, but all of these require a fair amount of space and I really wanted a solution that met the following goals: –

  • Low cost
  • As few components as possible
  • Easy to implement given reasonable soldering skills
  • Fits within the form factor of the existing card
  • Effective filtering across the audio band and beyond
  • Works within the existing PSU voltage limitations

Continue reading

Posted in Engineering, Music, Streaming | 6 Comments