CV Toolkit Updated With 5 New Modules & More

Spektro Audio has updated CV Toolkit – a Mac/Windows app that’s designed to let you integrate your computer as a control voltage source with hardware modular synthesizers.

The new update includes five new modules (Shift Register, Shaper, Delay, PWM Clock, and Euclidean Sequencer), support for the Expert Sleepers ES-4, ES-40, ESX-4CV, and ESX-8CV modules (still in an experimental stage but working fine according to my tests), a new pitch detection algorithm that vastly improves VCO calibration, and various improvements and bug fixes.

Here are details on the new modules: Continue reading

MST Eurorack Voltage Controlled Low Pass Filter Demo

Low_Pass_Filter-150x500Synthrotek has introduced the MST Eurorack Voltage Controlled Low Pass Filter – a collaboration with synth pioneer George Mattson.

The MST Low Pass Filter is a precision analog dual-slope output 2 & 4 pole filter. It offers simultaneous -12 DB and -24 DB outputs, with CV control over all parameters. It can also be used as a 1V/O sine wave oscillator.


  • Manual control of cutoff frequency
  • Manual Control of Resonance (Q)
  • 1V/O input for clean sine wave output
  • CV Frequency input w/ attenuator
  • Resonance CV input w/ attenuator
  • Audio input
  • Simultaneous -12 db and -24 db/octave outputs

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ADDAC702 Dual Voltage Controlled Filter Overview


ADDAC System has released a series of videos, demoing its ADDAC702 Dual Voltage Controlled Filter.

It’s the company’s first voltage-controlled variable filter, inspired by the original Korg MS-20 filter.


  • Two independent filters, a High-Pass and a Low-Pass with dedicated audio inputs and outputs.
  • Besides individual outputs the HP and LP are also sent to a voltage-controlled Mix between the HP and LP filters.
  • Both Cutoff and Resonance are voltage-controlled with dedicated cv attenuator pots.
  • Switch for selecting between normal cutoff behaviour and an adjustable Smooth circuit to simulate a vactrol behaviour for cutoff control.
  • Switch for setting filters Filters in Parallel, independent, or Series: HP into LP.
  • Inspired by the Oscar synthesizer we added a Coupling switch to tie the HP Cutoff control to the LP Cutoff control, in this case the LP cutoff controls act as an offset from HP setting.
  • Three position switch selects different resonance clipping paths: diodes / no clipping / leds.
  • Both filters features a post Distortion/Fuzz circuit that adds extra harmonics adds an even deeper growl or extra gritiness to it.
  • All audio outputs HP, Mix and LP feature a switch for choosing phase output, allowing additive or subtractive mixes.
  • Three LEDs monitor the amplitude of the three outputs: HP, Mix, LP.

Here are the official demo videos:  Continue reading