Erica Synths - Black Varishape VCO 1

Coming staight from the Russian vintage synthesizer Polivoks, this analog oscillator has a wide frequency range, a transistor-based suboscillator plus the bi-polar waveform mixer, allowing you to mix the waves with correct or inverted phase and to create plenty new waveforms this way.
But the very unique feature of the 1st of the two available Black Varishape VCOs is a special frequency modulation called X-mod.

Analog voltage controlled oscillator with stable tracking over 7 octaves which is pretty much for an analog VCO.
The Varishape VCO1's tuning controls consist of a seven-position rotary switch and a frequency control.
Besides the exponential FM input there is another one, called X-Mod. It derives from the original Polivoks' cross-modulation function and it has a much stronger, wild sound resembling radio noise at high modulation index settings. This feature is not found on the Varishape VCO2.

It has no individual waveform outputs but a mix output instead. For each waveform (triangle, sawtooth and pulse) a bipolar control is available which will add the wave to the mix, either with correct phase or phase inverted; this way the waves interact with each other and new waves can be created. The mixer turns into a wave shaper!

The pulse width can be adjusted manually or modulated via the scalable CV input. Same like on the original Polivoks VCO the triangle wave has a spike and is relatively rich in harmonics. The pulse width modualtion will also affect the triangle and thus it's sound which is similar to the original oscillator's behaviour.
In addition to the three waves a transistor based sub oscillator with a specific sound can be found which is added to the mix with correct phase.

The laggy transition when switching octaves is implemented on purpose. On one hand the glide is a nice effect and on the other this will omit audible clicks.