There are no known issues with the PCB.
Capacitor choice: Please note that the 1uF DC blocking capacitors C11 and C12 on the two audio outputs should be bipolar (non-polarized) capacitors, such as bipolar (NP) electrolyic capacitors or ceramics. However, the bypass capacitors C2 and C3 should be normal polarized electrolytic capacitors: they can be any value 1uF to 10uF, really. The other smaller capacitors can be any convenient type.
Please note that the correct value for C14 is 22pF. (An early version of the schematic showed 22nF.)
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).
Diode D1: use a 1N4148 (or a low-drop-out germanium diode.)
There is a difference in terminology between the 4HP and 6HP labels. We want to use the terminology “Breadth” rather than “Width” now, to signify it is not a relative amount (like a percentage, like the vanilla PW most VCOs output) but an absolute amount.
Workaround for Swapped Labels of 4HP Panel
The 4HP front panel has an error: the labels for Pulse Out and Sharkstooth Out are swapped.
If you have a 4HP panel with “Out Pulse” at the bottom socket, there is a simple fix for the swapped labels: swap which sockets the final resistors R18 and R19 go to. (If you have already fully populated the board, I recommend removing the ICs to give yourself more room to work.) Remove R18 and R19 if they are installed: they are at the bottom of the board next to the sockets. Install a 1k resistor in standing position between the top hole marked R19 and the neighbouring bottom hole marked R18. Then run a second 1k resistor in lying position between the remaining two holes; make sure you position it so that there will not be any accidental touching or shorts: position the body of the laid-down resistor to be next to the standing-up resistor, to reduce the chances of leads meeting, and try to position the resistor as far away as possible (you may prefer to use heat-shrink insulation tubing.) Reinstall the ICs.
Customizing: Pimp my Blip!
- If you find the modulation input is too weak (and you probably will), change resistor R22 from 47k to 10k.
- If you want a version of Blip! with fewer highs, play with larger values of C4 and C5 to filter the sound a wee bit.
- The +5V line on the power cable is not used by this module, so you may install a 10-pin power socket instead of the shown 16-pin socket, aligned on the red (negative) side.
Freak Out! 