This 8HP module is a Dual Ring Modulator module specifically designed for the Behringer System 55 or any Moog Modules in Eurorack. The module delivers a superb sound with ringing bell tones across a wide frequency spectrum and works with the lowel signal levels of a Moog Modular replica.
Description Moog never made a commercial Ring Modulator module, but did offer Bode’s design as standalone boxes in the 1960’s (Models 6401 and 6402). These are based on diode rings and transformers and are rather too large and heavy to fit into a Eurorack module!
In 1968 Barrie Gilbert invented a simpler and more efficient “four quadrant multiplier” circuit using matched transistors, and it is this design that most modern ring modulators are based on. The design was soon put into a semiconductor chip by Fairchild Semiconductor (possibly the first dedicated modulator chip – the ua796 of 1973). It was gradually improved and appeared as the 1494, 1595 and 1496.
Over at E-mu Systems Dave Rossum used a discrete transistor version in his Modular system (The 2430 module of 1973), whilst at Roland they used the ua796 chip in the System 700 Modular system (1976). The Bode Frequency Shifter of 1973 has two multipliers, using the new modulator chips, one is based on the UA796 and the other based on the MC1494. It is the ROland and Bode designs that have inspired the AM1631.
Ring modulation became a popular effect in the 1970’s and it was championed by ARP in their synths rather than by Moog. Roland picked up on the idea, and became a strong exponent in both the System 700 and 100M modular synths. Klaus Schulze will have used his ARP 2600 for ring modulation sounds (as the Moog Modular did not have such a module), and then perhaps he used the PPG 300 which has a rather nice Dual Analog Multiplier.
Design I designed a UA796 based circuit and manufactured an initial run of 10x modules using this chip and LM301A “can” style Op Amps, this was a very nice vintage module but a bit expensive! Additional batches of modules use the MC1496 Modulator chip and a LM1458 Op Amp, with PJ301 jack sockets replacing the Lumberg 1502 jack sockets.
Each ring modulator has a level control for the B input and an orange flat top LED showing the signal output level. The module works with Behringer System 55 Moog modules which have 2.6V p-t-p signals. The circuit is sufficiently simple to fit two Ring Modulators on a small 8HP wide PCB and it includes a modulation level pot and an orange front panel LED which indicates the output level.
Connections There are six 3.5 mm jack sockets on the front panel:
- 2x audio inputs for each Ring Modulator
- 1x audio output for each Ring Modulator
The module comes with a set of M3 mounting screws and washers, and a standard Doepfer power cable.
PLEASE NOTE: The modules should not be used with Eurorack modules which have larger signal levels (±5V p-t-p), please buy our AM1035 Triple Modulator instead.
Outcomes & Availability A prototype was produced in October 2020 and with a few modifications the first production run was in late 2020 using black anodised panels, and a second batch in Autumn 2021. The module was also available with a plain aluminum panel for use with standard Eurorack signal levels.
2024 Model The Moog Modular format AM1631 remains in production with a new front panel with an improved black finish, and the correct silver graphics and silver edge strips. Thanks to automated SMD assembly the price of the module has been reduced to £89!
