The RS909 is the TR-909’s analog rimshot sound generator in a Eurorack format; adding yet another low-cost analog drum generator from a legendary drum machine to your modular synthesizer and expanding your Tiptop Audio modular drum machine even further.

We use an exact reproduction of the original analog circuit for the RS909. Its sound is generated by a clever set of three T-bridge oscillators, each producing a damped sine wave at a different frequency. The mix of those oscillators goes through a VCA whose gain is controlled by an envelope generator providing the well-known attack that gives the sound its unique “feel”.

In the RS909, we bring frequency control of the two internal oscillators, OSC1 and OSC2, to the front panel, allowing for adjustment of their pitch, and thereby extending the sounds this circuit is capable of and allowing fine adjustment of the classic sound.

The RS909 includes a high-powered output gain stage capable of producing hot signals. On the inputs, we have designed a pulse-shaper circuit so you can trigger the RS909 with trigger/gate signals from step sequencers, clock dividers or any other pulse/clock sources. This eliminates the need to shape pulses sent to the module and ensures the same stable sound at peak power, regardless of your pulse source. Based on the architecture of the 909, the Accent input is versatile and able to take in both CV and Gate signals for continuously changing dynamics. All of these unique features make integrating this legendary sound generator into your modular synth easy, unleashing the power of real analog drums.