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  • 7 min read

Lab note: CMOS analog switch non linearity

CMOS analog switches are a very convenient way to pass signals around: they work up to MHz frequencies, they don't statically consume power and their two terminals can float arbitrarily between the rails. Their downsides are their badly characterized ON resistance, and the fact that it varies with applied voltage...

This has made them shunned in some audio circles, because this brings distortion. But I grabbed a whole bag of DG212CJ quad analog switches at 39C3, and it'd be a shame not to use them.

  • 9 min read

Caring for and designing with audio jacks

Audio jacks are... a mess. There are at least 4 different sizes, of which 2 are common, that are called by different names across the Atlantic. There's a variable number of contacts and at least two different schemes for using them. Originally designed for telephone exchanges, they're now used for general consumer audio as well as professional recording equipment. Some are even used for power, for connecting guitar pedals... The "jack connector" may as well be more of an idea than an actual standard.

Nonetheless, in the consumer space, today, there are de facto standard uses for jack connectors. Here, I try to provide an overview of what to expect when tinkering.

  • 8 min read

A good enough microphone example

Microphones! Who doesn't want a good one? Although digital voice processing has gotten more advanced over the last decades, most of you know the unfortunate reality of echoes that aren't completely cancelled, unsatisfactory or greedy noise cancelling and so on. At their core, these problems come from digital processing being unable to cope with very compromised recording setups. Providing decent recordings feels like politeness or hospitality to my call-mates. Commercial solutions are either expensive, or of unknown quality. Time to build one!

  • 13 min read

Desktop speakers, an exercise in avoiding feature creep

Contrary to hackENS, the hackerspace where I work right now does not have a woodworking space, which makes one itch for such projects. Being back home for one week for unrelated reasons, the obvious thing to do was a woodworking project! Besides, there's nothing like spreading chips everywhere and triggering smoke detectors with a friend.

  • 8 min read

Cheap PC sound cards: what can they do really

In the aftermath of a convoluted history, sound cards are one of the most well-supported and common peripherals you can encounter on a PC. Today, the general user can expect to simply plug a 3.5mm (or 2.5mm, if they're fancy) jack in their system and have it work. This dramatically falls appart once you try to do (or build!) something non standard. On the net, information about sound cards is sparse and vastly outdated, dating back to the Sound Blaster era... In this post, I collect knowledge about current computer soundcards, their limitations and some tricks to mitigate them.