The SIMMONS SDSV 80s Drum Brain

Simmons 80s Drums SDSV

An analog drum synth legend

You probably already heard a Simmons drum synth without even knowing it... wondering what was used to produce that huge drum sound?

The Simmons hexagonal shaped Electronic drums were all over the place, on countless records and live shows during the 80s , used by artists and bands like Genesis, King Crimson, Jean Michel Jarre, Prince, Herbie Hancock, Pink Floyd etc... The sound was not especially realistic but it was not the goal...the goal was to be huge and versatile. Invented by Dave Simmons, the most famous drum brain called the SDSV or SDS5 was a drum synthesizer, bringing synthesis into the drummer's hands.

Often used abusively to generate only those pewww pewww tom tom sounds, the SDSV module produced a wide range of sounds. With a great punch and sensitivity, a truly unique and cult sound, it can be used for almost everything. The SDSV successor called SDS7 bring some digital low-fi samples in the game and a bunch of additional features like bend direction or FM modulation for a broader range of possible sounds.

The SDSV is a historical piece of gear that has a place in the sound of the 80s and is still used today as a secret weapon. Only around 5000 of these things are out there so don't count on finding a working one easily or for cheap. The machine was made by a true innovator that later, unfortunately, lost his Simmons Company. As there were no accurate VST for this legend out there...

I had to make the VSDSX! This is dedicated to Dave Simmons.

The VSDSX VST, which stands for Virtual Simmons Drum System extended, provides the closest experience to the real thing, it models accurately the analog character of the sound generation, internal circuitry, clocks and counters that read EPROM memory, feed the 8bit DAC which decodes the hi-hat and cymbal EPROMS data in real-time. It models the SSM2044 filters with fine tuning control over lots of internal circuitry resistors. CV, trigger shapes, and VCA response can also be tuned to produce a wide range of sounds, and punch/response, this also emulates how the module will react if triggered with pads, Simmons pads or sequencer... Separate outputs for your DAW, velocity handling etc...You will obtain that legendary powerful analog punch! On top of the cake, one voice can load your own external EPROM data like on a real SDS1 (EPROM based) pad...This opens up onto a whole new range of sound, still being processed by the circuitry.

VSDSX provide a huge synthetic drum sound by itself and can also be used with great efficiency in drum layering.

Using it for layering with VPROM VST can really bring a nasty funky sound which combine analog and early digital!

Simmons SDSV Drum brain



VSDSX VST Videos & Sounds Demos Playlists.

The ultimate 80s drum sound!

VSDSX Simmons SDSV VST Features and Details


The special tone character of the drum synth is mainly caused by the raw analog waveform generation and by the circuitry itself, it generates harmonics that are normally not present in an ideal triangle waveform, VSDSX emulates that behavior and also models the analog clipping that occurs when pushed hard. You can also switch to a clean mode which will behave like an ideal system without OPAMP bandwidth limitation (more highs). These features alone offer a great versatility for sound design.


The sound source of the drum synth was mainly a mix between a triangle oscillator and a transistor based noise generator. The way it was initially connected could be tuned for more or less frequency content. Each voice has different configuration and VSDSX offers user control over the internal noise filtering (especially useful on the snare voice card).

A lot of the circuitry parameters can also be fine-tuned, CV and VCA response, Trigger types (that will mostly impact the click attack generator time) etc.

SSM2044 Filters

The noise source was filtered by an SSM2044 lowpass filter chip, the filter acts on the noise and click part and behave differently depending on the voice, on bass & toms the resonance resistor was usually set to no resonance, but this can be tweaked inside the VSDSX if you want.


One of the obvious things that must be there in a drum synthesizer is a pitch envelope to simulate the behavior of real drums. The SDSV module featured a bending down effect that can be set to more or less amount of bending. VSDSX also features a bend up option and an optional FM modulation taken from the SDS7 module.


The VSDSX have separate outputs for every voice like an original SDSV.

You can choose from ALL to 1 Stereo Channel or Separate Channels for each voice.


The drum synth is highly sensitive to the power of which a pad or a key is hit, VSDSX gives independent access to sensitivity tuning for each voice, the pitch of the tone, VCF cutoff, click trigger etc...You can also disable the volume velocity tracking and only set a pitch sensitivity which gives access to a similar feature than the "run generator" found in certain Simmons Systems.


The GUI features all the SDSV controls (with the same weird naming :) ) but can also give access to a full module display with more in-depth controls, most of the parameters can be MIDI learned and controlled by an external MIDI Hardware or automation.


The VSDSX provides one voice which is EPROM based (like SDS1 or SDS7) the imported sample will benefit from the bend and noise mixing feature with that crunchy 8bit sound.
Load your own custom made EPROM image. EPROM format is the same as VLINN for easy compatibility.

VSDSX supports the following type and size EPROMS binaries (.bin)

2716(2048_Bytes) 2K

2732(4096_Bytes) 4K

2764(8192_Bytes) 8K

27128(16384_Bytes) 16K

27256(32768_Bytes) 32K

LOAD & SAVE FULL PATCH & BANKS in FXB/FXP (additional technical info in manual.)

The Hi-hat & Cymbal modules were pretty rare and unique sounding, mostly they were sample based, same configuration for both cards, but in a very particular way.

Honestly, the metallic waveform has nothing to do with a real hi-hat or cymbal sound, you can hear its looping and the raw 8bit character, but: This is a CULT sound! If you play this with bending up or down while toying around with noise and filter, you get these famous cymbal sweeps!

Velocity can also act on the sample rate and it sounds pretty original.

Memory was expensive at that time so you cannot store a long sample and be cost effective.

So Dave Simmons looped the short sound stored onto a 2732 EPROM, a trick first used by Roger Linn in the LM-1 but this time, the sample is read forward then backward.

The loop plays all the time inside the SDSVs digital modules and only VCA and VCF are triggered, this configuration opens up to very long decay settings.

The 555 Timer is the clock which set the speed of sample reading, the CD4516 are the counters and the CD4013 is changing the readout direction once counter reach the end.

The data are stored as a linear 8bit format and decoded by the linear 8bit DAC.

Hihat EPROM based circuit

The original SDSV schematic and a lot of useful documentation found on the great website were priceless to design VSDSX VST.


Read the VSDSX Manual

Get amazing details about the Simmons SDSV Drum Brain and master the VSDSX!


VSDSX User Manual

Change Log

Update History

You can check your current version with a right click on the GUI.
Updates for VSDSX VST are free until version 2.0

07/01/17 - v1.1 06/30/14 - v1.0

Get It !

Get VSDSX for Windows

VSDSX will be ported to Native x64 and OSX in the future.