CASIO PA-31,
Casio KA-20,
Casio SA-8,
Casio SA-2,
Casio TA-10		 small keyboards with complex lo-fi wavetable sounds

These keyboards all belong to the Casio SA-21 hardware class, which was the direct successor of the Casio SA-1 hardware. Sound engine and behaviour are basically identical; the only difference is that the newer CPU supports 5 different demos (through 5 OBS buttons) and 5 drumpads. Due to the similarity I only describe here the differences to the SA-1 hardware (see there).

Casio PA-31

Casio PA-31

Unlike Casio SA-1, this instrument is 4 note polyphonic, plays samples with higher bit resolution and has 4 demo melodies. Unfortunately the digital volume control is gone, which on the SA-1 could be used as a sound effect to change the sample bit resolution and the speed of algorithmic preset sounds (e.g. mandolin ring).
The special feature of the Casio PA-31 in comparison to other such keyboards is the so-called "voice pad controller", which is simply a set of 8 sound effect buttons those play each a fixed low resolution sample (like drumpads), which pitch can be adjusted with a knob within a bit more than 1 octave.

different main features:

eastereggs:

notes:

All sounds of this instrument sound cleaner and less harsh than with Casio SA-1. I am not sure if the output DAC bit resolution is increased by external discrete components (demultiplexer?) or if it is just better filtered.

The "voice pad controller" is implemented by the independent CPU "OKI M6373-349", which clock speed can be adjusted with the big red knob to change the pitch. Unfortunately the effect pads respond too slow for fast trilled sounds and have only a monophonic sound generator. The low- res effect samples sound quite noisy but not harsh. (I haven't examined the hardware yet.)

The demos are nice and complex orchestrated although they are quite short (repeating in a loop) and the tune "Twinkle Twinkle Little Star" sounds almost like when the programmer forgot to add the main voice because most of the time plays only the accompaniment and 2nd voice (obligato?); the melody voice appears only for a few seconds as ringing mandolin. On the Casio SA-35 this tune indeed exists complete with main voice and there the main voice can be muted by hand to train playing.

Casio KA-20

Casio KA-20

This quite rare yellow toy keyboard was apparently the model for the widely spread and greatly bizarre sounding My Music Center, because it has many design elements and even some sounds common with it.

Both have a case with moulded handle opening at the top, 32 keys, 5 drumpad buttons and 4 edge protectors, although My Music Center is typically red with yellow plastic protectors while the violet protectors on KA-20 are of rubber. The percussion timbres of My Music Center sound even like low- res samples of the latter, both include a honky- tonk piano sound and multiple demo tunes, and also the arrangement of the wonderful "Jingle Bells" demo has noticeable similarities with the Casio model (regard the trilled notes) although they are not identical. The My Music Center is also much smaller and has mini keys while KA-20 has a midsize keyboard. An even closer case imitation of it was the Sun Ta Toys SDN BHD 1996, although its "Jingle Bells" is arranged differently.

Unlike the tinny My Music Center, the sounds of Casio KA-20 are astonishingly clear and even the speaker sounds pleasantly warm and has some bass. The KA-20 uses the same CPU like the Casio PA-31, but has only 16 sounds due to omitted cipher buttons. These are the differences to the PA-31:

different main features:

eastereggs:

notes:

The only 4 available cipher buttons {"1", "2", "3", "4"} of the Casio KA-20 correspond to the buttons {"0", "2", "6", "7} on the SA-1 (or PA-31). It is very recommended to add also the 6 missing buttons to get access to the 84 missing preset sounds buried in its CPU. (I didn't modify mine because I already own the PA-31. I haven't examined the hardware yet.)

A red, Japanese language keyboard with same case and ROM-Pack slot instead of the preset sound list, key lighting (LED row) and 8 OBS preset sounds(?) was released as Casio - Sound Kids 02 (alias Casio KS-02, I got the box photo from a collector).

Casio SA-8

Also this 2 note polyphonic instrument is based on the same CPU, thus I only will describe here the differences to the latter. Someone told me it was also released as Casio SA-3 and a green/ purple version as Casio SA-9.

different main features:

eastereggs:

notes:

This thing resembles basically my Casio PA-31 but is 2 note polyphonic and has only 25 sounds - apparently due to omitted cipher buttons. I guess it was the cheaper version of the Casio SA-6 (black, roughly oval mini keyboard) which has 100 preset sounds, 5 drumpads and 5 demos.

The only 5 available cipher buttons {"1", "2", "3", "4", "5"} of the Casio SA-8 correspond to the buttons {"0", "1", "2", "3", "6"} on the Casio SA-1. It is very recommended to add also the 5 missing buttons to get access to the 75 missing preset sounds buried in its CPU. Technically it is likely possible to upgrade the SA-8 with 4 note polyphony and all the other features found in the Casio SA-21 or also PA-31 (except "voice pad controller") because both contain the same CPU. But for this a diode would need to be soldered into the line of each key, and also the CPU needs to be switched into SA-21 mode (likely by a permanent diode somewhere in the keyboard matrix). The PA-31 contains also additional descrete components (capacitors and resistors); I haven't examined if these have to do with the keyboard matrix or if they only improve the sample resolution. (I haven't examined the hardware yet because I own already the SA-1 and PA-31.)

Casio SA-2

This lousy little tablehooter from 1995 (embossed case date stamp) is an even more crippled version of the Casio SA-8. It has no(!) tempo control, only 2 volume steps, only 16 preset sounds (due to 4 cipher buttons) and no drumpads anymore. A red version of it was released in 1995 as Casio KA-2.

Don't confuse the SA-2 with the similar looking Casio SA-5, which is way more versatile and has fantastic tekkno synth sounds.)

different main features:

  • only 16 preset sounds {piano, elec piano, honky- tonk piano, harpsichord, brass ens, warm brass, trumpet, tuba, samba whistle, whistle, quena, flute, strings, warm strings, violin, violin- piano}
  • only 4 cipher buttons
  • no tempo control
  • only 2 step volume slider
  • no drumpad buttons
  • CPU "OKI M6387-11, 5092301" (30 narrow pin DIL)
  • only 1 demo melody: "Choral (Beethoven)" [="Ode to Joy"]
  • no sound output jack

    • eastereggs:

    Very annoying is that this horrible crippled tablehooter has only a mechanical switch for 2 volume steps despite its CPU would support digital volume control. Also the omitted tempo buttons are inexcusable. The SA-2 is certainly good for circuit bending (all the missing stuff can be added by matrix eastereggs), but for not much else. (I would never have bought one of these but found mine in a junk pile after a flea market.)

    Casio TA-10

    This is basically a midsize Casio SA-8 with built-in stereo cassette player. This is not a cassette recorder despite there is a microphone for singing, and despite midsize keys it is only 2 note polyphonic. Due to extreme similarity I only describe here the differences to the SA-8.

    different main features:

    notes:

    This keyboard came with the German audio cassette "Mein Casio TA-10 Keyboard - probieren, spielen, lernen". With my specimen the cassette sounds detuned against the keyboard and plays a little higher; likely the cheap plastic tape drive runs a bit too fast. The first cassette side musically explains the functions of the keyboard. Then the player shall accompany an imaginary eerie movie scene with the "fantasy" sound.  On side 2 there are 6 German children songs. First it plays a complete version, then followed by only the accompaniment to play to.

    The 6 children songs are:

    1. Alle meine Entchen (="All My Ducks")
    2. Hänschen Klein (="Little Bee")
    3. Es tanzt ein Bi-Ba-Butzemann
    4. Meister Jakob (="Brother John")
    5. Vogelhochzeit
    6. Guten Abend, Gute Nacht (= Brahms lullaby)
    The songs are nice polyphonic arrangements and were likely played on one of the professional Casio workstation keyboards with its automatic accompaniment.
     

    Instruments of this hardware class also include the midsize keyboards Casio SA-21/ SA-38/ SA-39 (all same case, 5 drumpads, 2 speakers, 100 sounds) and the oval mini keyboard Casio SA-6 (100 sounds, 5 drumpads).
     

     removal of these screws voids warranty...    
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