While we wait for the enclosures to arrive, I’ve taken the time to implement a host of improvements to the multiboard PCB. And before our brave pioneers feel short-changed, the PCB is not functionally different in any way – rather the changes reflect sound design practice.
Here’s the new board.
For the following changes, I’m hugely indebted to Old Crow, a US-based synth builder with many years of experience (for a somewhat more involved DIY build than the Groovesizer, have a look at his crOwBX).
- All power traces are now 32mils.
- Lots of bypass capacitors – specifically on all of the multiplexer ICs.
- The 7805 voltage regulator is now flat mounted.
- The crystal and trim caps have been moved closer to the oscillator pins on the Atmega.
- A ground plane now shields the various circuit elements from one another and from clock noise.
- The serial input pin for 5th row 4021 is now terminated.
Thanks also to Mutable Instruments‘ Olivier Gillet for suggesting the use of a 6N137 optocoupler in the MIDI input circuit to replace the 4N35 I’ve been using.
Last but not least, thanks to Ewald Cress for insisting on the 1N4001 reverse polarity protection diode.