See the
Knifonium channel for previous posts including video.
"Knifonium is a 25 tube monophonic synthesizer with a 4th order ladder filter and a ring modulator.
Basic Specs:
Oscillator 1 (5 tubes)
-Sawtooth, Triangle, Pulse, Sine
-Sync
-FM
-Octaves 64, 32, 16, 8, 4, 2 -Coarse tune in semitone steps-Fine tune in +/- 100 cents.

Oscillator 2 (3 tubes)
-Sawtooth, Triangle, Sine
-is master for sync and modulator for FM
-Octaves 64, 32, 16, 8, 4, 2 -Coarse tune in semitone steps-Fine tune in +/- 100 cents.
Noise (2 tubes):
-Noise generator is a special tube that is subjected to strong magnetic field. -White, Pink and Red.
Ring modulator (3 tubes)
-Input is sine waves from both oscillators or anything from external inputs, feedback et cetera, drive volume can be adjusted
-Very wide nonlinear range available.
Mixer (2 tubes)
-A tube op amp, virtual earth mixer with one external input.
-3 of the input levels can be modulated.
Filter (7 tubes)
-4th order ladder filter.
-Can go from clean to messy to violent depending on levels and resonance.
VCA (2 tubes)
-Transformer coupled variable mu pentode design.
-More than 40dB of linear range. Capable of total shut down. A switch to increase internal level by 10 dB for nice distortion.