PLEASE READ THESE BEFORE STARTING TO POPULATE THE BOARD
There are two issues with the Rev 2 PCB that require fixes:
- Diodes D4 and D6 are no longer used. They limited the saw wave at high levels, but I prefer it without.
- Resistor R35 should not be installed in the expected place on the board. This resistor feeds the “Alt Out” output. Instead install the resistor in standing stance, with one end connected to the R35 inside hole as normal, but with the other end connecte to the neighbouring R1 resistor inside hole. This resistor feeds the Alt Out only.
If you have selected the 4HP panel, there is another fix required. The 4HP panel has the Out and Alt Out labels swapped. To fix this it is a simple matter to crossover the outputs:
- Do not install R38 and R40 normally. Install them standing up, so that one resistor goes between the inner holes of R40 and R38 while the other one (they are the same value) goes between the outer holes of R40 and R38.
R38 and R40 for 4HP
Capacitor choice: Please note that the 1uF DC blocking capacitors C5, C7, C8 and C9 should be bipolar electrolytics (non-polarized). The bypass capacitors C1 and C2 can be any value of polarized electrolytic =< 10uF, really. The other smaller capacitors can be any convenient type.
Knobs choice: the 4HP module is quite cramped if normal knobs are used. I recommend the t18 microknobs (available from Thonk, as use by e.g. Befalco), if you your pots have the same shaft width.
What’s with the name? The Fibonacci series is seen over the natural and artistic world (some great examples here) including some seashells notably the nautilus, so “Shell” seemed a good reminder. (Actually, seashells have a wide variation from the ideal Fibonacci.)
Freak Out! 