The Ensoniq SQ-1 is a digital synthesizer based on ROM waveforms (a ROMpler). It is patch-compatible with the Ensoniq SQ-2 (the 76-key version with the same engine) and the Ensoniq KS-32. It is also available in rackmount form as the SQ-R.
21-note and 32-note-polyphonic versions of the SQ-1 exist. The models are SQ-1, SQ-1 Plus, and SQ-1 Plus 32-voice. The plus versions have improved piano sounds.
It contains a set of 9 transwaves that can be used for wave sequencing. Here is the transwave list:
The CR2032 memory backup battery is soldered to the main board. When it dies, a battery holder should be installed in its place.
The front panel buttons are table-shaped and rest on a plastic frame. The legs can become bent or broken, causing buttons to be permanently pushed in. They are not difficult to replace if you can find spares.
The 1/4" audio connectors are plastic and not flush with the case. They can break and will need to be replaced with new ones, but they are fairly standard and a simple soldering job to replace.
Broken keys can be challenging because you have to completely disassemble the synthesizer to remove the keyboard, but once you've removed so many screws that your hand hurts, replacing a key is simple. The key return springs have a fair amount of tension, and you will need pliers to reattach them.
Internally, the SQ-1 has 3 circuit boards - a power supply board, the main board which is managed by a Motorola 68000 CPU, and the front panel display/button board.
To our knowledge there wasn't a copy of the SQ-1 Plus / SQ-2 manual available in PDF form, so we scanned our copy. It's available below.
Year Released: 1991
Keyboard: 61 keys with velocity
Polyphony: 21 notes
Multitimbral: 24 parts
Preset Patches: 100
User Patches: 80
ROM: 3MB (167 16-bit waveforms including 1 MB piano)
Dimensions: 1026 mm x 340 mm x 130 mm
Weight: 11.3 kg
Latest OS Version: 1.11
Latest OS Version For SQ-1 32: 2.03
Latest OS Version For SQ-1+: 1.15
Ensoniq SQ-1 1990-ish ($175)