Alesis S4 / S4 Plus

Alesis S4 Image

The QuadraSynth was introduced in 1993 by Alesis, and it was their first major synthesizer. The S4 is the rack-mount version of the QuadraSynth. It's a 64-voice digital synthesizer with a whopping 16 MB of sample ROM, and was the first synth to offer the ADAT Optical Digital interface. It also featured the same multi-effects processor as the QuadraVerb 2, drum kits based on the D4 drum module, 4 assignable control knobs, one PCMCIA card slot, 48kHz clock input, and 4 audio outputs.

The S4 is undoubtedly a powerful and flexible synthesizer capable of creating rich sounds - both acoustic and electronic. It uses digital additive/subtractive sample playback synthesis to create high quality stereo grand pianos, organs, strings, drums/percussion, brass, woodwinds, new and classic synth textures, and more.

Released in 1995/1996 came the new and improved S4 Plus version (pictured). The S4 Plus rack module came with only 20MB ROM, losing the coveted 8MB stereo Grand Piano sample found in the QuadraSynths in favor of 4MB of General MIDI pianos. For an all around versatile modern synthesizer module that isn't focused just on dance or trance, be sure to consider the S4 or S4 Plus.

Lookup Alesis S4 / S4 Plus Prices

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16 Visitor comments
January 9, 2014 @ 11:32 pm
I have this rack. The pianos remind me of the M1 era, but with more depth to the sound. The strings are really dance-y. The mellotron and a couple of the guitar/flute sounds are great. It's not a synth in my view, it's more of a pre-made sampler with a quadraverb built in and some good sounds on it for dance/rap music or soft arps.
July 2, 2013 @ 8:22 pm
S4 -VS- QSR. Opinions? Anybody?
I have a QSR. The stock acoustic type samples/patches sound too dated ain't worth doo doo & the filters are a bit weak. But with a little editing/tweaking, it's capable of some AMAZING Synth Pads. The Vintage Synthesizers Q-Card is pretty good. (probably the best Q-Card IMO) It's not in the same league as Roland's SR-JV Vintage Synth, but if the QSR had an appregiator, it would be nearly as good as Korg's EXB-PCM Vintage Archives. (which is actually a bit disappointing) I'd like to know how the S4 sounds, compared to the QSR. I see an S4+ on Ebay for $158.
May 4, 2013 @ 5:27 pm
Oops sorry, it was the QSR I was dissapointed with, the S4 I have no opinions about...
Svenn lemm
March 24, 2013 @ 12:41 pm
I´ve had one of these and the truth is that I was not very impressed,
has weak sounding filter wich I think is the synths biggest problem and
that really made it sound like sheit imho.

Eric B
February 2, 2013 @ 3:29 pm
S4 seems to have an extended bandwidth. Clear highs and deep bass are possible.

Behind typical 90's presets lives one of the better ROM sets of the period. Synth waveforms both analog and digital sound sophisticated. Filter is not resonant, but there are a few sampled sweeps. Piano has a good tone. Choir, mellotron, organ and strings sound very well. Included are some snappy drum samples of D4 variety.

S4's envelopes, modulation and the four sound "mix" architecture are strong points. Good effects as well. With programming it is possible to produce colossal, evolving pads.
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  • Check Price
  • The link above will take you to an eBay search for this synth to see active listings. If you don't find it there, try looking in our forum marketplace or post a wanted classified.
  • Demos & Media
  • YouTube Thumbnail
    S4 Plus Factory Demo.
    by eonporter1

    Manual - Alesis have made manuals and program charts for many of their products available on-line, for free download as .PDF files.

  • Specifications
  • Polyphony - 64 voices
  • Oscillators - 48kHz Linear samples
    S4: 16MB, expandable to 24MB using PCMCIA ROM and RAM cards
    S4 Plus: 20MB, expandable to 28MB using PCMCIA ROM and RAM cards
  • Multitimbral - 16 parts
  • Effects - 4 On-board effects, based on the Alesis QuadraVerb 2 FX processor
  • Arpeg/Seq - None
  • Keyboard - None
  • Memory - S4: 128 preset 128 user programs, 100 preset, 100 user mixes
    S4 Plus: 512 preset 128 user programs, 400 preset, 100 user mixes
  • Control - MIDI IN/OUT/THRU (16-channels)
  • Date Produced - 1993 (S4)
    1995 (S4 Plus)
  • Resources & Credits
  • Images from

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