Video Technology - Rhythmic 2

Video Technology

squarewave keyboard with accompaniment & analogue rhythm

This instrument from 1985 (bottom type sticker) may be the ancestor of all no-name keyboards with bipolar squarewave sound engine. Like MC-3 and its variants it employs the Yamaha 4 channel soundchip DSG, but unlike these, it additionally has analogue percussion.

The Rhythmic 2 has a black case, 1 speaker and some rows of differently coloured silicone rubber buttons (similar like the Testron ones).

This instrument was also released as Maitho PK2 and a red version as Power Sounds (seen on eBay).

main features:

49 mid size keys
tinny 3W loudspeaker
polyphony 4 notes (only 1 note with accompaniment)
separate knobs for main and rhythm + accompaniment volume
10 semi- OBS preset sounds selected by 5 buttons + shift button: {organ, music box, oboe, guitar, trumpet | clarinet, violin, harpsichord, accordion, piano}
10 semi- OBS preset rhythms selected by 5 buttons + shift button: {waltz, jazz waltz, disco, rock, rumba | march, 16 beat, swing, bossanova, tango}
sustain and vibrato button
4(?) percussion sounds (most are analogue, some may be digital)

base	= analogue click
hihat (?)	= shift register noise (?)
snare (?)	= transistor noise (?, more muffled than the hihat) with multiple volume levels
tom	= low squarewave (?) blip

auto-accompaniment in single finger chord or fingered (=normal) chord mode. (manual organ chord keyboard split when rhythm off) For such chords always the same, envelope-less squarewave organ tones are used.
arpeggio button (only usable during accompaniment)
rhythm fill-in button
tempo {+, -} buttons
transpose {+, -, reset} (0..-11 semitones, works only with accompaniment)
many red round status LEDs
multi-chip hardware:

CPU= "Toshiba TMP4740P, 5444 8814H, Japan" (42 pin DIL, crystal clocked @ 4MHz)
sound IC= "Yamaha YM2163, 7Z 02 83 G" (24 pin DIL | DSG)

4 demo melodies repeat in a sequence:

[classic tune]
Blue Danube
For Elise
Skate Waltz

jacks for AC-adapter, headphone

notes:

The hardware construction of this 1985er keyboard strongly resembles Letron MC-3, HBATEC, Testron, Fujitone 6A and the like, thus it apparently was an early predecessor of a series of Chinese so-called "no-name" instruments. Interesting is in this context that the Rhythmic 2 features as well the demo melody "Blue Danube" (which is the same like with my HBATEC keyboard) as "For Elise" (which is the demo tune of the Testron), although these versions are arranged differently. The accompaniments of the instrument's demo melodies various times miss the correct key (thus sound disharmonic) and are slightly out of sync, which sounds quite unprofessional. Like early Casio instruments, the Rhythmic 2 has a moulded, cylindrical plastic pot behind the speaker in the case bottom, but unlike good Casios, this one seems to make the sound rather cheap and canny than improving its timbre. Nowadays the company Video Technology is better known as VTech, which is a well known manufacturer of educational children computers; VTech otherwise is affiliated with Yeno, which was the manufacturer of the "Der kleine Musikant" toy keyboard.

The CPU "TMP4740P" is a documented Toshiba 4-bit microcontroller with 4KB ROM and 256 byte SRAM. Bizarre is that this chip with identical or similar software (same preset sound and rhythm list) was also used in keyboard kits or projects of the Chinese electronics DIY magazine "Electronics Practice" (of 1994?) as "KD-48" and "KD-49" (both differ in analogue parts?, schematics seen on Chinese websites, thanks Traktor for info). The KD-49 apparently can be even equipped with a 2nd DSG to increase polyphony (/CS+/WR of DSG1 wired to CPU pin 33, of DSG2 to pin 36), thus it may be that the Rhythmic2 CPU can support it too.

When I bought the Rhythmic 2 keyboard, the "fingered chord" and "tempo -" button didn't work due to a broken bridge trace on the panel PCB.

All non-percussion sounds are saw- and squarewave based (with different pulse widths and envelopes) and sound much like a C64. The soundchip (same like with Testron) internally re-assigns the same tone generators to different outputs, so in accompaniment mode only 1 channel remains at the right keyboard section for melody play. Interesting for playing are the 5 semi- OBS sound buttons those can be also pressed while keys are held down without stopping their notes. By rhythmically pressing these buttons many arpeggiator- like timbre changes can be created, though this button field can be regarded as a realtime sound control. The static voice assignment of the instrument is a little annoying, because in any chord modes only 1 polyphony channel remains for the user selected sound in the right keyboard section, no matter how many channels are really actually occupied with chords or other accompaniments.

The accompaniments insert a sort-of automatic fill-in every 4 measures, which can be a little confusing, but generally sounds nice. The complex accompaniment behaviour resembles a bit the Testron, although it permits less play tricks. The instrument seems to make no use of the digital metallic cymbal sound of the YM2163 despite it would have sounded more natural than the analogue transistor noise it uses instead. Possibly this instrument was initially designed for a predecessor of the YM2163 soundchip that didn't feature these percussion sounds.

A stereo variant of the Rhythmic 2 keyboard was the Rhythmic 6 (aka Saisho - Music Maker MK 500, seen on eBay), which has 2 speakers and an additional chord volume slider, but still the same preset and function button names although it has sliders instead of knobs and smaller buttons. Likely both belong to the same hardware class. A more advanced midsize keyboard by Video Technology was the great Rhythmic 8 (pitchbend wheel, strange drum machine with slide switches, synth that can be layered with main voice) and the later fullsize keyboard Rhythmic 10.

*removal of these screws voids warranty...*

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