Infrared audio transmitter and receiver

This is the final lab from the analog half of Learning The Art of Electronics. I've had the thing assembled in some solderless breadboards for over a year and decided to make some PCBs for it.

Here are some pictures of the assembled PCBs:

PCB milling (FlatCAM):

0.2 mm 30º V bit, 20000 rpm, 300 mm/min, 50 um depth, autoleveling.
Isolation (2 pass) + Copper clear on selected regions (missed some).
0.8 mm & 1 mm holes.

And the unpopulated boards out of the CNC machine:

The breadboard prototype can be seen on the "About" page of this blog.

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