The Tube Stereo Passive Ring Modulator

Built for Hainbach

This project came about when Hainbach contacted me about making a ring modulator unit for his lecture about early electronic music. As most of you know, Hainbach is an avid collector of vintage test equipment and actively uses the pieces to create unique and wonderful sound worlds. There weren’t and still aren’t a lot of companies making vintage-style ring modulators that work in a studio setting– they were always seen as a niche and obscure “un-musical” type of effect.

In fact, as many famous composers have known over the years, the passive ring modulator’s unique (a)tonality can be actually very pleasing! Sweeping the frequency of the oscillator allows the signal to be smeared and modified in ways that are very hard to describe.

For this unit, all transformers are from the top-quality Swedish manufacturer Lundahl. That includes the input, output and 4 pieces needed for stereo ring modulation. It is quite a lot of iron! The signal path includes both wet and dry sections for more or less subtle ring modulation with each section having its own tilt equalizer control.

There is also provision for external carrier signals to be inserted via the front panel jacks. These can be any line-level signal and very interesting sounds can be made with unexpected combinations here. As well, on the lower ranges of the frequency range of the internal oscillator, a nice tremolo effect is created.

The case for this unit came from Hainbach himself and is typical of the many vintage Siemens units that he owns.