21 July 2020
These instructions are for the Roland Juno-6, though they may be more or less the same for a Juno-60.
For analog synths, especially vintage, there can exist a significant tonal difference between individual units, despite otherwise identical settings and conditions.
The Juno synthesizer is prone to this, but with a small screwdriver, your ears, and about 2 minutes, there are steps you can easily take to help calibrate the Juno to your liking.
Begin by unscrewing the two screws on each side of the wood ends:
With these screws undone, the synth can be opened by gently lifting up where the front plate meets the keys.
The settings we want to adjust are the saw wave level, saw wave width, and square wave width.
The saw wave adjustments are located near the C4 key, on the board that lay flat. They have blue plastic trimmers like this:
On my Juno, the saw level was always too low relative to the square wave. Turning the saw level trimmer clockwise as far as possible greatly reduced this discrepancy and improved the fullness of the sound when the waves are combined.
The greatest tonal difference comes from adjustment of the wave widths. With just fractional turns of these trimmers, your synthesizer can sound vastly different- thinner or fuller, depending on how you set it. This difference is most evident when you combine the saw and square waves together, and especially when plucky sounds are used.
Here is a slow sweep of the saw width trimmer, with both saw and square wave engaged:
The tonal options available to the saw width trimmer are directly linked to the square width trimmer, so to achieve best results, experiment with combinations of different settings of each.
The square width trimmer is located on the left board, of the pair of boards mounted on the underside of the front panel. It can be hard to spot, but it is a small hole located near the lower-right region of the board:
In much the same way as the saw width trimmer, adjustments to the square width trimmer can have both small and large effects on tone. Here is a sweep of the square width trimmer, with both the square and saw wave engaged, as in the previous example:
The critical factor here is the sound of the saw and square waves combined. When adjusting these trimmers with each waveform in isolation, it can be difficult to identify the tonal changes being made. When calibration is done with both waves engaged, the differences are much clearer as the waveshapes combine and phase together.
Finally, the sound of a Juno calibrated for a rich, full tone, with some added FX (RE-501, PSP2445).