Single Pass Oscillator Calibration Tool
Introduction :
This is the tool we use for performing the volt-per-octave calibration of our Dual Harmonic Oscillator (DHO). The math and instruction are adapted from the datasheet of the Sound Semiconductor SSI2130 oscillator IC datasheet.
As this tool might be useful for anyone into synth DIY we decided to create this only tool and make it available to the world.
Disclaimer: Even if this tool has been extensively tested with many different oscillators but we do not provide any guarantee that it would work with your specific unit. Some, follow different mathematic principles and some, like in our own cDVCA Class D waveshaper, cannot be tuned using this tool.
A little bit of information: Sounds Semiconductor is the reboot of SSM by the original CEO Dan Parks and includes many members of the original team, including Dave Rossum. They have re-issued and improved upon the fantastic SSM2164 (now SSI2164) and SSM2044 (now SSI2144), which are at the core of some of the greatest sounding synths ever made. Additionally, they are now producing new, outstanding synth-specific ICs like the SSI2130 oscillator used in the DHO.
If you plan on creating your own synthesizer, you should absolutely consider using their products! You can purchase them at Thonk.
Tools Needed :
Voltage source, for example a well calibrated MIDI to CV
Some way to measure frequency
Multimeter in frequency mode
Oscillocscope
Audio interface and oscilloscope application (for example : MedalProduction MOscilloscope)
Procedure :
Plug in and let your oscillator warm up for a while
Send 1V (C1) in the V/Oct input of your oscillator
Write the 1V measured frequency in the tool.
Send 5V (C5) in the V/Oct input of your oscillator
Write the 5V measured frequency in the tool
Still applying 5V, use the V/Oct trimmer to adjust to the Target 5V frequency given to you by the tool
Once again send 1V to the V/Oct input of the oscillator
Measure the frequency once more
If the frequency matches the Target 1V frequency then your oscillator is calibrated!
Repeat from step 2 if this is not the case