Ring modulation takes two inputs and multiples them by each other. The original signals are canceled out, leaving only sidebands that are harmonically unique and often unpredictable. Of course, any mathematical model is less than perfectly carried out in the analog world, giving each implementation a unique character. Most modern ring modulators perform multiplication with a single integrated circuit. However, the concept of ring modulation was invented back in 1934 for use in telephone lines, long before the invention of the transistor.

This module uses the original circuit arrangement where vacuum tubes and transformers perform the multiplication. The sounds of the tube circuit tend to be more harmonically rich and complex. This module excels at making bell-like sounds, edgy, FM-like bass sounds, metallic percussion textures, and otherworldly sound effects. The inputs can be used with oscillator outputs, LFOs operating within the audio range, or any audio signal. Using the same envelope to sweep the frequency of an oscillator connected to one of the inputs and the amplitude of a VCA after the ring modulator output can lead to fascinating new textures. Varying input levels also affect the overall timbre.

All Stoel Music Systems modules feature aluminum front panels with a durable high-gloss white finish. For a crisp appearance and exceptional durability, the front panel markings are digitally printed at high-resolution with UV-cured ink. Mounting holes are plated to significantly reduce screw rash. The power connection features polarity protection to prevent accidental damage to the module if it is connected backward.

Each module includes a 12” long 10-pin to 16-pin ribbon cable compatible with the Eurorack standard, M3 mounting screws, and a complimentary sticker.

True vacuum tube ring modulation
Signal is driven through two transformers
The tube circuit tends to be more harmonically rich and complex
Can be used as a primitive VCA
Great for bells, edgy effects, and FM bass sounds

Technical Specifications

Width	14 HP
Depth	49 mm
Current Draw	+12V: 500mA, -12V: 7mA, +5V: 0mA

Vacuum Tube Ring Mod