Simple Gates is a dual low pass vactrol gate 4HP module with 3 filter types and a 2-pole mode in a 4HP DIY Kit. Inspired by classic Buchla designs, Simple Gates is entirely passive, drawing power from the incoming CV only.
Each low pass vactrol gate (2 in the module) has an input (on the left) and an output (on the right). Both are DC Coupled. The CV input is below and indicated by an LED and a lightning bolt symbol. CV can be applied to the CV input to open the gate (positive voltages above 1.2V open the gate). The gate can be more or less open depending on voltage applied. Short gates can be used to create plucky, percussive bursts of sound, or gradual, slow CV can be used to subtly shape the sound.
The three position switch switches between 3 different modes:
- LPG - A classic low pass gate frequency response. Fully closed, the cutoff is at 20Hz, fully open the cutoff is at 6KHz. Useful for audio sources and percussive sounds. This is the traditional sound most associated with LPGs.
- VCA - This mode applies no filtering to input signal, the frequency response is mostly flat. This is useful to add an additional VCA to your system, when waveshaping is to be applied elsewhere. This mode is also great for Amplitude Modulation and Frequency mixing - sending one frequency into the input and another into the CV input to obtain unusual signals on the output. Great for CV too.
- LOW - an Extremely Low Pass Filter - This mode has an off-state cutoff frequency at 0.1 Hz and a on-state cutoff frequency of about 800Hz. This is fantastic for bass synths or kick drum synthesis.
Once patched, it's easy to switch between the three modes to experience how each shapes the tone. You will fall in love with this flexibility.
The bottom CV Input is normalized to the top CV Input, and the top Output can be normalized to the bottom input (via a solder jumper on the rear). This allows a 2-pole mode where a source is connected to the top input, a control voltage signal to the top CV Input, and take the output from the bottom gate's output. This mode allows 2 poles of filtering, the filtering done by first the top vactrol gate and then the bottom. This allows 9 different modes of gating to further sculpt your sound.
The Simple Gates Kit contains all parts needed to assemble this module. This kit is appopriate for beginners, there are no surface mount components and all parts are large and easy to solder.