Unbenownst to me, my building the DIY (do-it-yourself)
Bottlehead Crack headphone amp was not only a way to get a great amp for cheap, it was a gateway into greater ventures. Namely building this:
This is the
β22 (Beta22), an open-source design for a reference-quality, all-discrete, class-A, solid-state headphone amp, renowned for its transparency. You can't just buy one (except by paying an exorbitant sum to have someone else make you one and ship it), you must build it yourself. And unlike Bottlehead, AMB barely holds your hand at all. They give you the schematic, sell a few of the parts (and recommend which ones to buy from third parties), and offer a help forum for when things go wrong. The electronics took at least forty hours of soldering, and the heavy sheet steel cases another fifteen hours of machining (they recommend buying a case, but I would still have had to machine the mounting holes and I preferred steel for its superior EMI resistance). I'm pretty sure this thing could support my weight.
The power supply, known as the σ22, is another electronics project in itself also designed by AMB, which I worked on mostly in parallel. Despite being about half the size of the β22, it weighs almost as much because of the toroidal transformer.
The construction was a laborious process. I started with bare printed circuit boards and hundreds of parts from Digikey...
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| One board... |
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| Two board... |
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| Three board. |
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| Four board! |
After the boards had been mostly populated, it was time to start connecting them together...
...and then set to work on the handmade case, which started out like this:
After a lot of machining, it was time for the final assembly!
So, the design and construction aside, how does the β22 sound? Like...nothing. Combined with my also-transparent HRT MusicStreamer II+ DAC and HD800s, I don't really hear my signal chain at all--only the music. It's possibly the most transparent sound system I've ever listened on, except maybe some Stax electrostatics I got to try at a headphone meet.
