CASIO PT-7 w/ Original Box

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via this auction

2nd one this month

"Near Mint Condition Casio PT-7 with Original Box, Operation Manual and Brand New Batteries Included (instrument with tiny polyphonic touch sensor keypad & analogue rhythm)

This is clearly one of the most bizarre and innovative instruments created by Casio, because this tiny thing has a detachable keyboard with 29 soft touch foil keys, and this is not just a monophonic toy tablehooter but a real 8 note(!) polyphonic instrument with analogue rhythm and a small but high quality loudspeaker that makes a very respectable organ sound.

This strange Casio invention permits special play techniques with very rapid glissandos and was one of the forgotten milestones in the struggle of overcoming the clumsy piano key relic on electronic consumer instruments.

main features:

29 tiny soft touch foil keys on a detachable slim line keyboard with short cable

built-in astonishing reasonable sounding small speaker

8 notes polyphony

separate knobs for main and rhythm volume

tempo knob

6 preset rhythms {waltz, samba, swing, slow rock, pops, rock} selected by a slide switch

8 OBS preset sounds {piano, elec. piano, organ, pipe organ harp, accordion, clarinet, violin} selected by a 4-step slider + switch

main voice CPU "HD44140, 3G 13" (56 pin SMD) with timbres based on multipulse squarewave tones with different digital envelopes, those are differently low pass filtered through capacitors. It makes very warm and pleasant timbres, but envelope release phase is truncated too soon, which makes piano- like tones less natural.

rhythm IC "NEC D8048C 316, 8322X7" (40 pin DIL, same like in Casio MT-40) that outputs trigger pulses for analogue drums

analogue percussion {base, snare, open cymbal, close cymbal, clave}; cymbals and snare use transistor noise.

jacks for AC adapter & headphone

eastereggs:


vibrato and sustain switch addable

up to 8 additional keys addable (makes no sense here)

holding down multiple sound select buttons during play makes wild cacophonic sounds (likely keyboard matrix mess by missing diodes).

possibly bass accompaniment (with additional keypad) addable

rhythm shitshot button addable

notes:


The main voice sound chip of this instrument is the same like in the Casio MT-45. It plays high quality analogue timbres, those although not always natural, reproduce a warm and pleasant sound; it does not sound typically C64- like thin, but resembles rather full- size home organs of that era. Like with Casio VL-1, the release phase of main voice envelopes seems to be linear and thus sounds unrealistic since it fades silent too soon with an audible end click. When sustain is switched off, all sounds stop almost immediately after releasing the key. When sustain is on, sounds with decay envelope (piano, elec. piano, harp) ignore the key press duration and sound always with a fixed duration instead. The "elec. piano" sounds like a banjo, and also the normal piano resembles more a picked string. The "harp" and "organ" sounds seem to add a bit of analogue distortion (or a mixed suboscillator with very short independent envelope??) during attack phase. All sounds include a mild vibrato. The smooth touch sensor keypad responds quite sensitive and permits special play techniques with rapid note clusters and polyphonic glissandos (but no portamento - this is not a theremin!).

Attention: Never play with sharp, spiky or rough objects (like finger nails) on the sensor keyboard surface - the foil may get damaged easily.).


circuit bending details


The main unit of this instrument is crowded with 3 stacked PCBs those contain the rhythm IC and a lot of analogue components. The PCBs are partly shielded by aluminiumized cardboard - likely to prevent interferences in the transistor noise generator of the analogue percussion. The detachable keyboard hangs on a very short, shielded 4 lead cable that apparently only conducts supply voltage, GND and the main voice audio signal. The keypad contains a small SMD PCB with the HD44140 CPU, various discrete components and a clock oscillator with 2 trimmers (for pitch tuning?).

Attention: The sensor keyboard case is held closed by 3 tiny screws and 4 plastic tabs; to open it it is important to pull the plastic cover backwards (in the direction of the cable hole); do not bend it upward because this would crack off the plastic tabs. Be generally extremely careful with dismantling this delicate component.

Unfortunately the Casio PT-7 with its special glissando keypad seems to be one of the rarest Casio keyboards at all (I yet saw no other specimen on eBay yet) and I also never heard of any other polyphonic instrument with this kind of controller. The same main voice sound like the PT-7 had also the Casio MT-45 and likely also Casio MT-11 and MT-21, but they all have ordinary midsize keys."