Multi-Timbral Phase Modulation Sampler

Assimil8or Software v3.02 has been released. Check the Downloads tab for details or please click here to download the software update.

The LOCUTUS MIDI Mediator expansion module is now available from Rossum Electro-Music dealers worldwide.

Designed to provide a powerful, flexible sampling engine for modular synthesis, the ASSIMIL8OR Multi-Timbral Phase Modulation Sampler module is the latest incarnation of Dave Rossum’s decades-long pioneering of affordable professional sampling technology.

ASSIMIL8OR provides eight independent channels of sampling with sound quality that can range from extremely hi-fi to low fi, all with extensive real-time CV control.

Key ASSIMIL8OR features include:

  • Eight-channel multi-timbral operation. Each channel will be available from its own independent output as well as appearing in the stereo mix output.
  • Superb 24-bit A/D and D/A conversion.
  • Mono or stereo sampling. Channels can be configured as eight mono voices, four stereo voices, or any combination. (Well, any combination that adds up to eight).
  • The ability to assign up to 8 samples to each channel and select between them in real time via CV.
  • DC coupling through the signal path for sampling of control voltages.
  • Unique timbral capabilities with the ability to phase modulate samples by external analog signals or by other samples (a first, we believe).
  • Variable sample fidelity with independently selectable sample rate and bit depth.
  • Real-time CV control of bit depth.
  • Real-time CV control of aliasing (from virtually none to lots).
  • Extensive sample manipulation and looping capabilities.
  • Sample scrubbing under CV control.
  • One-shot or gated sample playback with variable attack and release times.
  • Gate/trigger inputs and CV inputs for each sample that can be assigned independently for each channel to virtually any sample parameter. Examples include:Pitch
    Bit Depth
    Phase Modulation
    Sample Start
    Sample Length
    Loop Start
    Loop Length
    Release Time
  • A front panel accessible SD card for sample and preset storage.
  • And a lot more…

ASSIMIL8OR is available now from Rossum Electro-Music dealers worldwide.


Assimil8or Specifications


2,300 seconds at 48kHz mono, freely allocatable between the 8 channels


48kHZ, 96kHZ, 192kHZ

A/D & D/A

24 Bits


32 Bits


100 microseconds at the Mix Outputs

180 microseconds at the Individual Outputs


Sample L/R

2x 3.5mm mono socket

100kΩ Input Impedance

Gate/Trigger 1-8 

8x 3.5mm mono socket

100kΩ Input Impedance

1.6V threshold

Control Voltage A 1-8

8x 3.5mm mono socket

100kΩ Input Impedance

96 kHz sample rate

Anti-alias filtered to 20kHz bandwidth

Control Voltage B&C 1-8

16x 3.5mm mono socket

100kΩ Input Impedance

48 kHz sample rate

No anti-alias filtering


Mix Outputs L/R

2x 3.5mm mono socket

1kΩ Impedance

Individual Outputs

8x 3.5mm mono socket

1kΩ Impedance


+/-12V via 16-pin, Doepfer-style connector


220mA +12V, 30mA -12V


28HP (W); Panel to power connector (with connector plugged in) 25mm (D)


1x Micro SD card
1x 16-pin, Doepfer-style cable
4x M3 screws
4x M2.5 screws
4x Nylon washers
1x Quickstart Guide

Assimil8or Introduction and Overview

An Assimil8or introduction and feature overview by sound designer Mike Kiraly for the Sonic Scenarios Video Series for Control.

Assimil8or 2.0 New Feature Demos

Dave’s Introduction to Phase Modulation

Phase modulation is a new kind of audio cross-modulation for sampled sounds.  It can produce rich and varied timbres and textures, as well as wild distortions and grating noises.

The word “new” is probably not accurate.  Modular synthesizers have used frequency modulation (FM) since their inception.  Low frequency FM produces nice vibrato effects, and audio rate FM creates interesting timbres.  But exponential FM alters the perceived fundamental frequency of an oscillator; linear FM is required to alter the timbre while staying on pitch.

When we use FM, we call the source of the modulation the modulator, and the oscillator being modulated is called the carrier.

In the early 1970’s, John Chowning discovered using digital oscillators that linear FM through the zero point (so the carrier actually reversed its oscillation) produced very diverse and pleasing timbres.  Yamaha further developed this technology, but while Yamaha continued to call their implementation “FM”, they actually were using Phase Modulation.  Also worthy of note, Don Buchla heard Chowning say that you couldn’t do “through zero” FM with an analog circuit, so Don did just that with his Music Easel’s Complex Oscillator.

Let’s look at some oscilloscope photos to understand the difference.  If I frequency modulate a sine wave with another sine wave, the ‘scope shows us the effect on the waveform.  (The modulator is on the bottom in blue, the carrier in yellow on the top):

Now let’s use a pulse waveform to modulate a sawtooth wave carrier:

Here you can see that when the pulse is high, the sawtooth gets steep, when it’s low, the sawtooth slope is slight.

Now let’s use “through zero” modulation and turn up the gain of the modulator to show how the sawtooth slope now goes downward (backward) when the FM goes negative:

Now, a big problem with through zero linear FM is that as the pitch of the modulator goes up, it has less effect on the carrier’s timbre.  Here’s the same setup as above, but with the frequency of the modulating pulse wave increased by 1.5 octaves.   Note that the carrier waveform is getting to be pretty much an ordinary sawtooth.

The solution, as Yamaha discovered, was to instead of modulating the carrier’s frequency, have the modulating oscillator modulate its “phase.”  What this means is that the modulator is directly changing the location in the carrier’s waveform, rather than changing the rate that the carrier oscillates by moving along through its waveform.  Here’s what a sawtooth phase modulated by a pulse looks like.  When the pulse goes high, the carrier skips ahead to a higher point in the sawtooth ramp; when it goes low, it skips back to a lower point.

But now when we increase the modulator’s frequency, the carrier is still dramatically affected.  And we can see also in this waveform cases where the pulse has skipped backwards or forwards over the sawtooth’s edge, creating more large edges at this point.

We can modulate the sawtooth with a sine wave too.  Here, you can see how phase modulation maintains the character of each waveform, giving a new timbre with the characteristics of both the modulator and the unmodulated carrier:

As a final example, here’s the waveform that results when a sawtooth is modulated by a violin sample.  The frequency and sharp edges of the sawtooth are maintained, but the complex timbre of the violin is added:

When first planning Assimil8or, I thought phase modulation might be a neat feature.  I was really surprised to find almost nobody had taken advantage of phase modulated sampled sounds.  My first few experiments were really exciting, and I hope you have fun exploring this capability of Assimil8or.

Download the latest Assimil8or software.

The latest version of the Assimil8or software is 3.02__240403. Click here to download version 3.02_240403.

Assimil8or software version 3.02 includes bug fixes and is recommended for all users.

  • Indexed KZ is a new MIDI Multi Assignment mode in which 8 successive keys act as index keys to select a channel’s zone, but do not trigger the channel. Indexed KZ uses a new MIDI Setup parameter, Index Base Key, to set the low note number of the index keys. 
  • Index Base Key is a new MIDI Setup parameter enabling users to select the low note number governing zone selection for MIDI Assignment mode Indexed KZ. (For example, with the Index Base Key parameter set to 1, MIDI notes 1 through 8 will select Assimil8or zones 1 through 8.) 
  • Zone Lock now works on a per-channel basis. Zone Lock now interacts with MIDI Multi Mode similarly to non-MIDI zone selection methods.
  • The Wave Scope on the home page now tracks and shows the locked zone when Zone Lock is enabled.
  • Version 3.02 introduces a fix for a bug which prevented linked channels from transposing with MIDI note number data.
  • Version 3.02 includes various minor tweaks and fixes.

Assimil8or Software v3.0 or later is required to use LOCUTUS. Please click here to download version 3.01_231120.

The 3.01_231120 update includes a bug fix is and strongly recommended for all users. Rossum recommends that all LOCUTUS users update to the latest Assimil8or software.

The latest version of Assimil8or software is 3.01_231120. Please click here to download version 3.01_231120. Assimil8or Software v3.0 or later is required to use LOCUTUS. Please click here to download version 3.01_231120.

The 3.01_231120 update includes a bug fix is and strongly recommended for all LOCUTUS users. Rossum recommends that all LOCUTUS users update to the latest Assimil8or software.

The 3.01_231120 update removed Phase Mod Source CV gain (attenuverter) field from the Phase Mod page. No change to underlying data. (The parameter is unused in actual RT playback.)

The Assimil8or 3.0 software introduces improvements to editing samples and loops and is required to use new MIDI functions enabled by LOCUTUS.

Selecting the Sample Start & End and Loop Start & End/Length parameters from editing shows the “micro-editor” field. (In previous versions, this “micro-editor” always had an orange background color.)

If the “micro-editor” is shown for editing these start and end points, double-clicking ENVELOPE turns on the option to snap to zero-crossings. The “micro-editor” color will be blue.

If the “micro-editor” is shown for editing start and end points, holding ENVELOPE while turning the DATA 1 encoder steps by +/-500 sample points.

A visual representation of the playback position is shown when editing Sample Start & End and Loop Start & End/length.

Version 2.05 is a bug fix release that addresses a number of issues (listed below):

Changes in version 2.05:

All files and folders with names beginning with “.” will be explicitly treated as invisible/hidden. This addresses issues with loading and importing sample data.

The names of wav files created by sampling are fixed to conform with the requirements of the memory card’s FAT32 file system. This addresses very rare issues rising from sample names automatically generated from preset names that contain any of the characters   ” * / : < > ? \ ^ |

The appearance of the Solo/Mute labels has been updated for visibility and to set them apart from preset parameters.

This bug fix release is recommended for all users.

Version 2.03_200318 (released March 18th, 2020) is a bug fix release that addresses a number of issues (listed below).

Changes in version 2.03_200318:

– Fixes a bug that could result in a sample not being properly saved after user sampling.

– Fixes a bug that could result in a sample not being properly saved after truncation.

– Fixes a bug that resulted in display lockup when displaying a sample of fewer than 1728 samples.

– On the Sampling Setup page, adds a “Wait” alert after sampling while the sample is being saved to card, then switches to the Erase Recorded Sample dialog.

Assimil8or software version 2.0 adds a host of powerful new features and workflow enhancements. Refer to the Assimil8or 2.0 Software New Features Guide for all the details.

Changes in version 2.02_20032:

New Feature

Zone Flip: A “Flip” function has been added to the Zone Operations menu. With a zone selected, use the DATA 2 knob to select the number of contiguous zones (starting with the selected one) to flip. Click the DATA 1 encoder to execute the flip. The order of the selected zones will be reversed. The zone voltage ranges will not be modified.

This will be useful when you’ve done a Chop or Explode and want to play the resulting zones in order, first to last, playing low to high on a keyboard (or sequencer) using one of the keyboard balances.

Workflow Enhancements

Zone Lock Indication: The zone number now flashes on any page where it appears to indicate that Zone Lock is enabled.

Sample Monitor Indication: The “L” and/or “R” indicators now flash subtly whenever sample monitoring is enabled for their respective sample input channels.

Also fixed a minor unreported bug and did some display polishing.

Changes in the previous version 1.11_190917.

This release fixed a bug that prevented Assimil8or from loading more than 1000 sample “sides” (a mono sample is one side, a stereo sample is two sides). Consequently, you could not load more than 500 stereo samples or a combination of mono and stereo samples that totaled more than 1000 sides. You can now load up to 1000 samples regardless of the mix of mono and stereo.

Changes in version 1.10_181001:


– File lists (files in folder file browser, sample lists, and folder lists) now display in alphabetical order.

– The sample inputs can now be monitored in the Mix outputs. Set this function on the Pan/Mix screen. The left and right inputs may be set individually. Choices are:

Off: The input will not appear in the mix output.

On: The input will always appear in the mix output.

Auto: The input will appear in the mix output when sample arming is “armed” or “HOT” and will not appear in the mix output when sample arming is “unarmed” or “Safe.”

These settings are saved as part of Sampling Setup.

– Channel Solo/Mute. Channels may be individually soloed or muted. This can be accomplished in two different ways:

1. On the Pan/Mix screen, cursor to the desired channel and select ““ (normal), Solo (S), or Mute (m).

2. At any time, press and hold the Pan/Mix button and press a channel button to solo that channel. Hold the Pan/Mix button and press the channel button again to return it to normal mode.

At any time, press and hold the Mutate button and press a channel button to mute that channel (Mutate, Mute, get it?). Hold the Mutate button and press the channel button again to return it to normal mode.

Solo and Mute settings are persistent across new preset selections and new folder loading.

Solo/Mute Indication – The channel number of any channel that is muted (either because it has been directly muted or because one or more other channels are soloed) is displayed in gray on the Loaded Channel Map and Selected Channel Map.

Solo/Mute Reset – Pressing  Mutate+Pan/Mix together clears all solos/mutes.

Help Text – There is scrolling help text (with timeout) describing the hidden key presses, when any solo/mute parameter on the Pan/Mix page is highlighted.

Bug fixes

– Fixed a problem that could cause a display lockup during Channel Copy.

– Fixed a stereo sampling bug where the left side of a stereo pair (Master channel) was not correctly initialized as part of the pair immediately after sampling, resulting in the right side not triggering when the left side was triggered.

– Fixed a bug that resulted in improper levels of newly formed stereo pairs when editing a channel’s Mode.

– Fixed a problem where a preset set to Auto-Trigger would start before all of the preset’s samples were loaded. New behavior: presets with multiple samples wait until all samples are loaded, then Auto-Trigger.

–  Fixed a problem where sample length would be shown as “0″ on Sample Info dialogs (Channels and Zones pages) for unloaded samples. The dialogs now display the correct length for unloaded samples.

Changes in version 1.03_180502:

Improved: Increased maximum visible folder count on a card from 128 folders to 1024 folders.
Improved: Hard truncation of a stereo sample now updates next channel’s sample selection if the channel was properly configured for stereo/right.
Fixed: Disappearing cursor on waveform displays with very long samples.
Fixed: Samples that had the ‘#’ character in sample name wouldn’t load.
Fixed: Some samples wouldn’t load due to an odd sized ‘inst’ chunk in the WAV header.
Fixed: Preset 199 didn’t get erased when loading a new folder.

Check your Assimil8or’s Software

To check the version that’s in your Assimil8or, press the UTILITY button to bring up the Utilities screen. Scroll down to About this Module and click the encoder to see the currently installed version.

Update your Assimil8or’s Software

To update your Assimil8or’s software, download the zip archive at the bottom of this page, then:

1. Unzip the archive, copy the “app” file to the root level of your micro SD card, and insert the card into the front panel slot on your Assimil8or.

2. Select Utilities > Load Software and click the encoder.

3. Assuming you inserted your SD card in Step 1, click the encoder as instructed.

4. If all goes well (which it almost certainly will), you will see a success message and instructions to turn the encoder and then click it to reboot your Assimil8or with the new software.

5. If an error is detected during the process, an error message will be displayed and you can try again.

6. Enjoy your new software.

Please click here to download version 3.01_231120. Assimil8or Software v3.0 or later is required to use LOCUTUS. Please click here to download version 3.01_231120.

The 3.01_231120 update includes a bug fix is and strongly recommended for all LOCUTUS users. Rossum recommends that all LOCUTUS users update to the latest Assimil8or software.