The transistor and diode ladder VCFs have been around almost since the dawn of the synth era, but depended on precisely matched semiconductors, temperature control, and the occasional beating. With the right kind of nonlinearity, vacuum tubes can do the same thing but without the hammer.

The Voluptron has a 4-5 octave cutoff frequency range (or more if you're willing to go beyond the bounds of 1V/oct CV). Its resonance capability extends up to self-oscillation, and at lower frequencies the audio signal can adjust the cutoff slightly — FM synthesis with a vacuum tube circuit.

Specs

Power budget

• +12V: 35 mA
• -12V: 35 mA
• One Illuminox Prime connection for plate and heater

Width

Max depth

Tubes supplied

Tubes compatible

• 6AQ8
• 6BK7
• 6BQ7
• 6CG7
• 6DJ8
• 6ES8 (best CV accuracy)
• 6FQ7
• 12AT7
• 12AU7
• 12AV7
• 12AX7
• 12AY7
• 12BH7
• 12DW7
• Other 9-pin dual triodes may work if the pinout matches those above; please contact us.

Demo

Further reading

PDF manual

Mini demo video

Perfect Circuit demo