POTEX
SUPER JAM
LO-FI TOY KEYBOARD WITH MANY GREAT DISTORTED CHORUS SOUNDS

This noble looking design object is likely the world only keyboard which right case half can be flipped back for 2 player music play and audiogames. Although the timbre has similarities with My Music Center, in detail the sounds are quite unique. They all are strongly distorted with cold chorus and grainy zipper noise, but this thing rocks! Jimmy Hendrix likely would have loved it. There are 128(!) sound variations but unfortunately the preset sounds are transposed to different notes and a polyphony bug skips notes during fast polyphonic play. But it is still definitely a great lo-fi sound source that with some presets even can sound like a trashy old analogue synth.

Unlike My Music Center the instrument is 7 note polyphonic, the waveforms are more natural (e.g. sonorous pipe organ bass), the bass range is warmer, envelopes are more variable and each of the 32 preset sounds can be changed with the "tone effect" button into 4 envelope variants. The sounds have strong analogue distortion and by this the pulsing tremolo of the chorus effect warbles duller and brighter in a unique way. Bright sounds resemble a sitar or my Nigam - Bulbul Tarang, but there are also many nice, almost analogue sounding dreamy synth brass timbres with warm distortion. In flipped state each keyboard half can be set to a different preset sound, and there are 4 audiogames. The instrument has also 5 drumpad and 4 effect pad buttons with spring noises and SF space laser stuff. But like with Kawasaki Pro37 the so-called rhythms are only loop samples those here include beside drum loops (usable for tekkno) also funk, rock, heavy metal and hiphop accompaniments; the tempo control simply pitches them up and down (like changing the speed of a phono record). Unfortunately the user interface has some flaws, fast polyphonic play often skips notes, and the preset sounds are tuned differently, which is very confusing (but can be compensated after adding a pitch control potentiometer). Annoying is also that the volume of the harsh and thin sounding speaker can not be set lower than medium ambient volume. But despite all annoying flaws this is a great and unique sounding instrument.

caution: Before flipping the right case half you must press the black keyboard release button below the speaker to unlock the mechanism. The plastic latch inside is far too flimsy and otherwise will crack off when not properly unlocked.

Someone e-mailed me that in USA this keyboard was also released by DSI with (counterfeit?) "Yamaha" logo (green case, yellow speaker, strange license sticker from Yamaha Motorcycles (not musical instruments!) on the back), and that also a light blue version came out (possibly released by Oregon Scientific).

main features:

Let's Jam!Come On!

modifications:

notes:

The operating concept of this instrument resembles Casio SA-35 or Yamaha PSS-7; the preset sounds are selected through group buttons those each cycle through multiple sounds. The selected sound is played during button press, and without rhythm most other buttons play a base drum noise, which disturbs live performance. The user interface also has other flaws; e.g. the stop button always resets the volume to medium, and the tempo control only takes effect after the accompaniment sample passes its loop point, which usually causes a delay of multiple seconds. Other Potex instruments could control their sample playback speed perfectly (the great Beat Square - Mix Evolution even backwards). In unmodified state the speaker sounded extremely thin and harsh, which made the bass part of the accompaniments almost inaudible. Gluing a thin adhesive foam rubber strip (window insulation foam) inside the rim of the white speaker cover fixes this and makes the sound quality at least fairly ok. On the case bottom is a "demo" switch, which switches the auto power- off time between short and long. (I haven't analyzed the hardware further yet.)

The sound programmer must have been on drugs or dyslexic, since many presets sound not remotely like what their name suggests, and very annoying is that many preset sounds are tuned to wrong notes (mentioned below). Also the strong chorus effect makes most sounds unrealistic. Like with My Music Center the preset sounds are not realistic but have a synthetic cold chorus timbre with zipper noise and some DAC aliasing noise in high notes. But unlike the latter, here the timbres are more natural and contain analogue distortion that makes them sound more vivid and also the bass range of some sounds is warmer. (Empty batteries increase the distortion.) Also the envelopes sound more variable here and like with Feng Yuan 28061 the chorus tremolo speed varies with the note pitch (the higher the faster). Flipping the right case half (by 12° is enough) switches the instrument into keysplit mode; now the preset sound group buttons 1 and 2 control the left half while 3 and 4 control the right half (thus each half has only 16 preset sounds available). In this mode an annoying polyphony bug in each half randomly truncates its notes when more than 2 keys are pressed.

The "piano" resembles the My Music Center one but is less detuned and held notes decay slower. Also "trumpet" (tuned to D) resembles the My Music Center one, although this one is less harsh and can not reach that high notes; the bass range is buzzy and disharmonic. "pipe organ" (tuned to G) is a halfway realistic metal pipe organ rank with sonorous bass range. "tuba" has too slow attack, sustain and a dull synth brass timbre with mids resembling a french horn; high notes rather resemble a metal flute. "violin" (tuned to D) sounds like on My Music Center; "saxophone 2" resembles "violin" with a more brassy waveform; the slow attack is very unrealistic and it sounds more like synth strings. "bell" has sustain and doesn't decay (not realistic); it rather resembles a bowed glass, although with high notes the chorus tremolo is too fast. "elec. guitar" sounds like a semi- hollow acoustic guitar with quite fast decay; longer key press makes note shorter. "music box" (tuned to D) resembles a glass celesta, but the bass range sounds dull like an acoustic guitar. "flute" resembles a metal flute with slow attack and dull bass range. "church organ" is a slightly brighter variant of it and with 1 second long sustain. "strings" (tuned to D) resembles a cello in the bass range; high notes resemble a pipe organ. "saxophone" (tuned to D) sounds in the mids halfway realistic; the bass range grunts buzzy and a bit disharmonic. "banjo" sounds halfway realistic. "hammond organ" is not realistic at all but resembles a metal pipe organ rank with slow attack and 1 second sustain. "harmonica" has the same envelope with a duller semi- brassy waveform that in the mids resembles a french horn. "jazz guitar" resembles a slightly thin harp. "honky-tonk" is no piano at all but is a dull synth string or reedy clarinet timbre with slow attack. "brass" (tuned to D) is also wrong; it resembles a reed organ timbre with very sonorous, warm and buzzy bass range and loud sustain that suddenly stops after 1 second. "cello" (tuned to G#) has the same envelope with semi- brassy string timbre (resembling a french horn). Also "english horn" (tuned to D) has the same envelope with a thin waveform resembling an oboe or harmonica. "clarinet" (tuned to G) is another hollow synth brass timbre with sustain. "harpsichord" is the same in slightly brighter. "horn" has the "brass" waveform with another french horn timbre. "oboe" (tuned to G) is a harsh brass timbre with slow attack and sustain. "accordion" (tuned to D) is too hollow to sound realistic. "harp" sounds ok (envelope like "jazz guitar"). "alto sax" (tuned to D) has slow attack and rather a harsh strings timbre; only medium high notes are halfway realistic. "strings 2" (tuned to D) is another pipe organ rank with warm bass range, slow attack and 1 second sustain. The "mandolin" rings with 8Hz. "xylophone" (tuned to B) sounds only in the mids remotely realistic; the bass range resembles rather a fast decaying e-bass. The "percussive organ" is not percussive at all, but yet another synth strings timbre with slow attack and 1 second sustain.

The "tone effect" button cycles each sound through 3 additional envelope variants. Variant 1 modulates the volume envelope with a kind of bell clang texture that turns faster and slow again and then stops; it truncates the now always held notes after 1 second and sounds very unique. Variant 2 sounds like the original but the pitch slightly howls down during attack and howls up again after key release; the effect is quite gentle and mostly audible in the bass range. Variant 3 delays the chorus subvoice of the preset sound by half a second, which with percussive sounds like a simple echo and with sustaining sounds gently changes the attack timbre.

The drumpad buttons are numbered "drum 1" to "drum 5" and play the samples {gong, closed hihat, low tom, base, high tom}. The gong is a 1 second long Chinese gong. The base may be also a muted tom. Also the 4 effect pad buttons are only numbered. "1" is a scratchy up howling sort of spring noise. "2" is a spring boing noise. "3" is a high laser zap quickly followed by a synth tom. "4" resembles a shot riochet noise that howls up and resembles an SF space laser sound. When the case is not flipped, the 4 audiogame buttons play a 5th effect sample, which is another spring boing noise layered with a howling sheet metal rattle (like the ghost noise from very old horror movies). The monophonic record/ playback sequencer behaves like with My Music Center, but drumpads can not be recorded. Strange is that during playback the only still active buttons are "tone effect" and the 5 drumpads, but not the effect pads.

The 10 preset "rhythms" are drum loops and accompaniments (of little use for melody play) those are simply loop samples of fixed- key, thus the tempo control also changes their pitch by simply changing the sample playback frequency. A confusing flaw is that tempo control only takes effect after the accompaniment sample passes its loop point, which can take a few seconds.

The accompaniment patterns are:

  1. fusion accompaniment (with trumpet)
  2. rock rhythm (base + distorted snare)
  3. tekkno rhythm (distorted base, kind of train noise)
  4. hiphop rhythm (drum kit with odd metallic buzz)
  5. funk accompaniment (wokachika e-guitar, e-bass)
  6. hard rock accompaniment (e-guitar, drum kit)
  7. fusion accompaniment (with tuba, e-guitar, boom noise)
  8. house rhythm (?, distorted base with handclap)
  9. slow heavy metal accompaniment (distorted e-guitar, drum kit)
  10. funk accompaniment (e-guitar, e-bass)
The 4 audiogames are for 2 players and only work when the case is flipped. They are selected with the "G1" to "G4" buttons. 2 red LEDs indicate which player is up. Other toy keyboards with flippable case halves are the Sound Mixer HMP-288 and the Super Electronic Keyboard (case details like Super Jam with more buttons, clear blue with black case, box shows yellow and silver, seen on eBay). Another My Music Center variant by Potex with way less flaws is the Cyber Keyboard and another My Music Center variant with lots of sounds (including the Super Jam pipe organ and brass timbres etc.) is the great Elta- EK-491 (49 midsize keys with even a simple synthesizer and MIDI out).
 
 removal of these screws voids warranty...    
WarrantyVoid
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