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Differential Audio

FS-256 Additive Synthesizer

FS-256 Additive Synthesizer

Regular price $2,600.00 USD
Regular price Sale price $2,600.00 USD
Sale Sold out


Patent Pending

The product is not yet available for purchase and is still under development, it is not 'Sold Out'.

Initial limited product launch will be made to subscribers of our email list.  Sign up to our email list at the bottom of this page or the home page to receive infrequent notifications about product status and initial availability. 

  • FS-256 product name is subject to be rebranded
  • Rendered and prototype images are not fully representative of the final product
  • Product price is subject to change before launch

Thank you for your understanding as we work to bring this product to market Q4 of 2024.


Engineered and assembled in Canada, the FS-256 includes walnut side panels.

Shipping & Returns

Shipping is included free of charge. Please see our return policy for details.


Length: 350mm (13.7")

Width: 220mm (8.6")

Height: 100mm (3.9")

Dimensions subject to change

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FS-256 Features

The FS-256 is a powerful polyphonic and multitimbral desktop synthesizer that generates sound using additive synthesis, which sums multiple sine waves together into a final output. Patent Pending.

  • 256 additive oscillators of 32 sine wave partials each (8192 total sine waves).
  • Each partial is independently controlled with user defined envelopes, over a range of variables.
  • 8 4-partial additive LFOs per additive oscillator with user programable envelopes.
  • 2 sine wave LFOs per partial for user defined AM and FM modulation per partial.
  • Easy to use patch oscillator assignment, allowing for up to 128 polyphony and 16 multitimbrality matched to MIDI channel inputs.
  • Real time FFT display of channels
  • Dual 5" 800x480 touchscreen for GUI and to define partial variable envelopes
  • 24 fully continuous rotational potentiometers for high resolution relative rotation (not absolute), allowing for patch load from SD card.
  • Wide range of analog outputs and inputs.

Welcome to the world of Additive Synthesis

Create beautiful, textured and unique sounds only possible through sound design from the ground up.

Solving The Additive Synthesis UI Problem

Additive Synthesis has historically been hindered by the huge amount of control data needed to be input by the user to control the behavior of the many partial sine waves. The FS-256 has a patent pending solution to this problem, by providing the user with a simple but powerful user interface, that allows the user to input large amounts of control data to the system, with simple swipes on the dual touchscreen interface.

The user generates envelopes that describe sine wave behaviors over time with respect to MIDI Note On and Off commands. This is achieved by drawing curves on the touchscreen that define stages in time with respect to MIDI commands, similar to Attack and Decay times. Each sine wave partial can have a different time for that stage, depending on how the stage time curve is drawn. The user then draws another curve on the 2nd display that sets the value for each partial for that stage.

As a result, an additive oscillator (comprised of 32, 64 or 128 sine wave partials), can be defined to have a sound unlike anything found in subtractive synthesis, as each partial has its own unique envelope defined, for a number of parameters as described in the Sound Design section below.

Hardware Features

  • Fully balanced stereo 1/4" Line Out, Line Out Aux (TRS, +4dBu).
  • Fully balanced stereo 1/4" Line In (TRS, +4dBu)
  • Dual mono 2.5mm 5VP-P analog in and out
  • Headphones 1/4" (TRS)
  • MIDI In and Thru
  • Micro SD card for firmware and patch storage
  • USB device mapped as external drive for firmware update and patch load/save to host PC

Sound Design

Each of the 256 additive oscillators in the FS-256 generate 32 indepentantly controlled sine wave partials which are summed together to produce the output of a single additive oscillator. Each sine wave partial can be independently controlled by generating envelopes via the touch screen displays for the following parameters:

  • Partial Amplitude
  • Partial Frequency
  • Partial AM Frequency
  • Partial AM Gain
  • Partial FM Frequency
  • Partial FM Gain

The user generates the envelopes to define these parameters by drawing curves on the touch screen display to set time and values from MIDI Note On and Off. This solution reduces the complexity of inputting such a large amount of data required by additive synthesis. Envelopes are not limited to a traditional ADSR pattern. This gives you full control over the sonic evolution of a sound - from rise and fall times of each partial amplitude, frequency deviation, AM and FM modulation per partial. Each partial has its own sine wave AM and FM sine wave LFO.

There are an additional 8 4-partial LFO's dedicated to each additive oscillator, that control global AM, FM, amplitude and frequency controls for the oscillator as a whole.

The front panel encoders allow the user to control a sound for a range of parameters, such as: detune, LFO freq and gain, oscillator partial spacing, rolloff and partial enables.

Voices, MIDI, Polyphony, Multitimbrality

Each of the 256 additive oscillators in the FS-256 are identical, and are treated as resources to be assigned to voices. When a patch is loaded from memory or created from scratch, the oscillators required for the voice are allocated from the pool of available oscillators with mixing handled automatically. This allows the 256 additive oscillators be allocated in a wide range of configurations.

Additive oscillators can be assigned into groups that prioritize polyphony, meaning that the oscillators are grouped to generate a common sound, but can be activated together for a larger polyphony. Conversely, the oscillators can be grouped together to form more sounds (multimbrality). This allows multiple sounds (instruments) to play concurrently.

There is a tradeoff between polyphony and multimbrality to share the oscillator resources in the device. Do you want a diverse orchestra with many solo instruments, or one big polyphonic snare drum band? Any range between the extremes is possible.

Spectral Resynthesis

Spectral Resynthesis is a method of synthesis that recrates a reference signal from a sum of sine waves, as only can be done with an additive synthesizer. The FS-256 supports real time spectral resynthesis (currently supporting a sum of 1024 sine waves), by analyzing signals on the analog input ports of the device, then recreating the signals in real time using a sum of sine waves.

The signal can be regenerated with or without modification, allowing for a wide range of new possibilities for the sound designer.

More details to follow.

Performance, Song and Voice Modes

Voices can be created, saved and loaded to work on sound design for a particular voice.

Saved voices can then be moved into 'Songs', where different voices respond to assigned MIDI channels for a song composition or performance.

Songs can be arranged into 'Performances', arranged from 'Songs', for quick select to move from one song to another with the voices loaded automatically.


The FS-256 come built in with multiple sound effects, powered by its own dedicated ARM processor.

Future Features

Future featues may include, via firmware updates:

  • Polyphonic aftertouch
  • MIDI Sysex
  • Share your voice patches with the community with author and patch name recorded.
  • Free Shipping

    Note: shipping policy is subject to change, but the plan is:

    Shipping is included in the purchase of the FS-256. Purchaser is responsible for any import duties and taxes of their home country.

  • Warranty

    Note: warranty policy is subject to change, but the plan is:

    A one year limited warranty is included with the purchase, registration required. Warranty is subject to terms and conditions (don't spill a beer on the unit).