by Janne Isotalo - published 2021-02-06
An article about how to calibrate your PROGUE synthesizer
Like many vintage-style analog synthesizers, Progue has trimmers that need to be set in order to achieve the proper "1V/OCT" -tuning. The first section of this article has a Get-It-Over-With -section for those who are eager just to get the synth in tune. The latter part of the article will do A-Deeper-Dive with explanations about the key concepts of the 1V/OCT calibration procedures.
All of the nine trimmers (VR1-VR9 on the PCB) can be accessed from the panel holes with a small-sized flat head screwdriver. The adjustment screw on the SMT trimmer is tiny, so if your screwdriver doesn't fit the hole in the panel it won't fit the trimmer either. The only other tool needed is a tuner that is connected to the synth's output. You can also use an digital oscilloscope or even only your ears if you have a reference tone (A=440Hz) available. The procedure is very similar in many analog synth.
Start by carefully adjusting the panel settings to match the settings in the drawing. Connect a midi keyboard to the PROGUE midi input and play Low-A. The proper octave might vary depending on your midi controller. With the Low-A key pressed, the frequency you will hear should be somewhere around 50-60Hz.
The first step is to calibrate OSC1. Adjust the following:
The second step is the octave switch calibration. Adjust the following:
The third step is the Hi-End calibration. Adjust the following:
Repeat the first and the third step for OSC2. You can also use the OSC1 for reference. The most important thing is the "beating consistency" between OSC1 and OSC2 in all octaves.
The VCA offset trimmer VR8, adjust the following:
The filter emphasis trimmer VR9 (single-turn) can be used to limit the maximum Emphasis (resonance) level when the Emphasis potentiometer is at maximum (CW). Adjust according to taste.
That's it, all done!
..will be continued soon..