There are no known error issues with the board. The Rev 3 PCB is a blue ROHS-compliant PCB.
- Please note that C5, C7, C8, C9 are bi-polar capacitors (non-polarized-NP). You could substitute a suitable non-electrolytic at a pinch.
- The circuit does not depend on any exact capacitor values, so you can substitute neighbouring values.
- You can substite BAT85 for BAT43 or even 1N4148 if you wish, though the last can result in a variation of the waveshape.
- You can substitute higher quality e.g. 5532 op-amps instead of TL072.
- If the main output level is too high, substitute R34 for a smaller value, e.g. 68k or 47k. The Alt Out will also drop.
- Make sure the shrouded power header has its slot facing into the board, not facing out.
- Note there is a capacitor called “1nF” (a typo) which may also have a value 1nF.
There are no known issues with the 6HP panel, however the 4HP panel has a workaround below.
4HP Panel Adjustment
R38 and R40 for 4HP Panel (Vers 2 board shown)
Note that the 4 holes for MOTM power connecter near the Eurorack connector are for non-Eurorack users: do not worry that these are empty. Also, note that the holes marked as test points also will not have components attached. They are there to help debugging, testing.
The 4HP panel has the Alt Out and Out labels swapped. If you have selected a 4HP panel, then you should crossover R40 and the adjacent R38. Mount them upright, so that one resistor (both are the same value) goes from inner hole to inner hole, while the other goes from outer hole to outer hole. They will not physically cross over each other.
Interoperability Issue: Inadequate Input Levels
A user has reported that their VCO modules generate much smaller signal levels that Shell expects. Shell was designed to take the Eurorack standard of typically 10V PP (+/-5V) and were tested to work (less well) with +/-2.5V. However, a user reports a module that only generates +/-2V.
Obviously, it is no answer for us to say “Why don’t you use modules that fit in with the standard Eurorack levels?” The immediate workaround for users is to amplify inadequate signals, if they can. We are looking at whether different threshold values in Shell can correct this problem, and we will update the Release Notes or BoM to provide alternative values if we find them.
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