Alesis Quadrasynth

Alesis Quadrasynth

Alesis Quadrasynth keyboard Alesis Quadrasynth S4 Module
W × H × D (mm)	1220 × 115 × 355 (keyboard) 482 × 43 × 150 (module)
Rack units	1U, full width (modules only)
Weight	13.6kg (keyboard) ~2kg (module)
Keyboard	76 keys
Manufacturer	Alesis
Release date	1994-1995
Standards	General MIDI
Parts	16
Max polyphony	64
Normal presets	Programs: 128 factory + 128 user (original models) 512 factory + 128 user (Plus models) Mixes: 100 factory + 100 user (original models) 400 factory + 100 user (Plus models)
Effects	Variable, see effects.

The Alesis Quadrasynth is a 76-key keyboard synthesizer released in 1994 by Alesis. It is the first device to incorporate the "QS Composite Synthesis" synthesis to produce sounds. It features a 16 Megabit ROM which features high quality, uncompressed sounds.

The name "Quadrasynth" was likely chosen as they have previously used the "Quadra" moniker for their Quadraverb lines of effect units, but also possibly because there are up to four elements that can make a program, and there are four knobs featured on the front panel that lets you modify parameters with ease.

Internally the keyboard seems to be referred to as the S5 - it is similar to the module version (the S4), however it incorporates mechanisms designed for keyboards such as the keybed, bender wheels, aftertouch sensors and more.

For the time it ended up gathering favourable reviews from publications, citing its easy-to-use interface, multitimbrality, expandability and large (for the time) 64-voice polyphony being obvious positives, with the filter being cited as a downside. Uniquely, or perhaps as to be expected with Alesis products of the time, the user interface itself is unconventional - rather than relying on a character display like the U-20 and JV-80, or a fully dot matrix display like the XV-5080 or the Korg M1's, they opted to use a custom LCD that has a dot matrix display for patch names, with the bottom section being entirely dedicated to displaying bespoke elements that can be highlighted.

Picture of Alesis S4 Plus's display in editing mode, showing most of the individual segments as active. Take note that the currently selected menu is underlined.

All the models feature a compliment of MIDI IN/OUT/THRU ports, as well as a digital output, a 48khz clock sync input, 2 pairs of outputs, PCMCIA expansion and a headphone jack. Depending on the model, the power input can be a 3-pin kettle lead type (similar to PC power supplies and other home appliances), or a special 4-pin DIN that delivers 9V AC power.

The keyboard version features in addition to these a complement of sustain and expression pedal inputs, which are missing from the module version as they are irrelevant there.

The Quadrasynth and S4 modules shipped with two built-in demo songs - "Cyberfunk" and "Bach's Bad Dream (with apologies to J.S. Bach's Prelude in Am)", both sequenced by Stephen Kay.

Synthesis

The QS Composite Synthesis standard is used across every Alesis Quadrasynth and QS line of products, it is comprised of 64 total voices, with each note being able to use up to four. This is comparable to the Korg ai² in terms of features, and to the Roland JV-1080 in terms of voice count and the voices-per-note figure.

The filter employed is a non-resonant type similar to the one on the Korg M1 or the Korg 01/W. To compensate for this, on-board waveforms feature multisamples with various resonance levels, which can be assigned to different velocity levels or pitches depending on the patch that is designed.

Each voice has access to an amplitude envelope and LFO, a filter section (with LFO and EG), a pitch modulation section, as well as a modulation matrix specific to that voice. These are then fed to an effects section - four buses are available, but the way these are organised and routed depend on the selected layout.

Effects

All effects information was collected with help from the manuals, as well as emagic's SoundDiver 3.0 software.

Configuration #1 - 4 sends, 1 reverb

4 FX sends are available in this mode - the first three sends each have their own independent pitch unit that controls chorus and/or flanging. Afterwards, each of the 4 sends has their own delays, which can have their own independent delay and feedback time. These can all be routed to the singular reverb unit in this mode, if desired. The pitch mode can all be changed independently, but only the first two delay instances can be changed, while the latter 2 are locked to "Mono Delay"

On the Plus models, the third pitch unit is hard locked to a "resonator mode" for this algorithm. This concession was made to provide higher fidelity for the other effects in this configuration.

Configuration #2 - 4 sends, 2 reverbs

4 FX sends are available in this mode, but only the first send has a delay unit, which is hard-set to Mono Delay. Two pitch units exist, one on FX send 1 and one on FX send 3, with only the first one being modifiable from "Mono Chorus". FX1 & 2 get summed up towards Reverb 1, and FX3 & 4 get summed up towards Reverb 2, both which are fully configurable.

Configuration #3 - 4 sends, 1 lezlie (sic)

4 FX sends are available in this mode - it is set up similarly to Configuration #1, however the first pitch unit is replaced with a Leslie simulation.

On the Plus models, the third pitch unit is hard locked to a "resonator mode" for this algorithm. This concession was made to provide higher fidelity for the other effects in this configuration.

Configuration #4 - 2 sends, with EQ

2 FX sends are avaliable in this mode - each going through one pitch unit, and then one delay unit - fully modifiable. Both get summed up into a reverb, which is also fully modifiable, which then gets output to a 2-band shelving EQ.

Configuration #5 (only available on Plus models) - Overdrive > Chorus > Delay > Reverb > Leslie

4 FX sends are available, but only FX1 gets access to the overdrive module - introduced in the Quadrasynth plus series. All the modules here are fully editable, and with exception to Overdrive can all be routed to any effect send (but not multiple). Terminates with an equalizer module.

Behind The Scenes

According to an interview with Marcus Ryle, one of the synth designers behind the Quadrasynth, he stated he had wanted to create a synthesizer that is simple to understand and edit, but can be quite complex. In the article, it's also noted that the reason filters are non-resonant was to achieve a higher polyphony count of 64 voices, and that the design philosophy was largely inspired by the team's prior work on various Oberheim products, like their Matrix 6.

It is easy to see some of these aspects in the final product: The bespoke LCD that makes editing easier than it would be on a 2-line unit, the quad knobs that allow for easy sound manipulation, or the variety of modulation options - all cited as sort-of bullet points the team wanted to achieve with their design.

Much like how they reused technology from their effects unit of the time, Alesis would also end up using many of the sounds they recorded and produced for their drum machine lines of products, like the Alesis D4, as a basis for the kits available on the unit.

Terminology

The Quadrasynth line divide their sounds into two different types:

• Mixes, which comprise of multiple programs playing concurrently, similar to Combi mode on Korg synthesizers or Performance mode on Roland products.
• Programs, which can comprise of up to four different voices. This is similar to the Prog mode on Korg synths, and the Patch mode on Roland products.

Alesis Quadrasynth S4

This is a rackmount version of the Quadrasynth, released in 1994. It is contained in a similar chassis to their effect units (notably the Quadraverb 2 even features a similar looking screen). Unlike the keyboard's orange-tinted backlight, the module version features a green backlight instead. In addition to the standard complement of I/O, the S4 and S4 Plus feature Alesis ADAT inputs and outputs accessible via optical ports. It could have possibly been used to interface with ADAT equipment of the time. This model and the S4 Plus also use the 9V AC 4-pin DIN port for power delivery. For more information, please see our power supplies article.

Alesis Quadrasynth Plus Piano

This is an upgraded version of the keyboard model, released in 1995, adding a further 3 banks of non-editable presets and mixes, which include a General MIDI bank and mode. The latter is selectable from the settings, although a GM Reset SysEX message will also set the synth up appropriately. It also expands the effects section to be comparable to that of the Alesis Quadraverb Q2's, and adds a further 8 megabits of ROM for various new types of sound, as well as a new piano. Some sounds have been added to existing voice groups, but for the most part two new voice groups have been created - "QSPlus" and "Rhythm" The v2.0 firmware also adds a few new smaller features, like a new Random LFO selection that is unipolar, and also implements bank switching via MIDI CC#0.

The demo tracks have been replaced as well, three new tracks and a shorter version of Bach's Bad Dream is available, albeit it seems to set the pitch bend ranges for the square lead errorenously. It is unknown if these new tracks have any names or who composed them at this time however it is likely the same person who sequenced the original two demo tracks, Stephen Kay.

Beyond firmware, the keyboard body has been recoloured from gray to black. It and the module would also include a software called Sound Bridge, which could interface with a PCMCIA card to upload extra samples. Notably, it could load SampleCell formatted files as well. These cards could also be used to store extra programs and mixes if desired.

Alesis Quadrasynth S4 Plus

Illustration of the Alesis S4 Plus, based on a version found in the manual with added colour.

Released in 1996, this is a rackmount version of the Quadrasynth Plus Piano, except it omits the extra piano sounds, for a total of 20 megabits of sample ROM. Software-wise, it is identical in all other respects. The QSPlus bank has been renamed to S4Plus.

The rackmount body itself features a few changes: "EXPANDED ROM - GENERAL MIDI" text can be found below the 8 buttons on the left, a bracket below the PAGE pair of buttons indicate that these can also increment or decrement a value by 10, the VALUE pair of buttons have a similar bracket, but for incrementing or decrementing by 1, and the logo has a fancy "Plus" handwritten on top of the logo.

Oddities

• On the original and the S4 models, using the bank CCs would not change the current bank. This was fixed for the plus releases.

• You could upgrade from the original model to the plus model via a ROM swap, which was way cheaper compared to buying a new synth. This was labeled as a v2.0 upgrade in some publications, as well as in the Plus manuals.

• While the officially released expansion cards will work with any Quadrasynth or QS unit, on the original non-plus models you would need to copy the card contents into the user memory, wiping out any custom patches or mixes one may have made. This is not the case with the plus models or any of the QS synths.

• While PCMCIA cards were common back then, only specific cards will work with Alesis synths - it requires a specific generation of Linear Flash memory, and it seems like specific Cisco cards will work for this purpose. Normally these synths can only read up to 8 megabits, although with mods it may be able to read beyond that.

• Alesis devices of the time employed the use of BR2325 batteries. If replacing a battery, one can instead solder a CR2032 battery holder in its place and use a CR2032 battery inside with no issues. For more information please consult the replacing backup batteries article.

• Although rare, the Quadrasynth can display quasi-error codes. For example, if there is no battery detected (or if the battery failed), it would not boot up, instead displaying a screen with all segments turned on, except the indicators for MIDI channels 1-5 and the MIX program number would read "_3".