Bontempi ES 3000   digital squarewave keyboard with drumpads & cheesy accompaniment
Thompsonic TS-37

Bontempi ES 3000

This very rare Bontempi keyboard is the small brother of the Elite MC2200; it is technically and soundwise very similar but has less features. So the custom drummer was replaced with a simple chord sequencer to make better use of the short keyboard.
The main voice is 2 note polyphonic squarewave and it features single finger chord accompaniment and 4 drumpads with low-res sample percussion. In unmodified state this tablehooter roars ear- tormenting loud out of its tinny speaker because the 5 step volume slider can only switch between silence, too loud and even louder.

This instrument was also released as MC-2100 (by Medeli?) and Thompsonic TS-21 (seen on eBay).

(Note: This keyboard may sound nice, but don't buy one of these so far your only intention is to get a keyboard with faithfully imitated natural instrument sounds. Remember, this is a squarewave instrument and though many of its sounds sound not even remotely like what is written on its buttons, though bought with wrong expectation it may disappoint you.)

Due to strong similarities with Elite MC2200 I only describe here the difference.

different main features:

eastereggs:

  • 2 higher note keys addable.

    • modifications:

    notes:

    This instrument resembles very much the Elite MC2200 but has no key split sounds, no song bank, only 8 rhythms and instead of the custom drummer a rather useless chord sequencer. Interesting is that Bontempi here redistributed a piece of MC-series hardware (manufactured by Medeli?) made in China. For reasonable use of this instrument, the far too loud volume switch urgently needs to be modified and a sound output should be added. My specimen operated very poorly, because solder joints at the AC-adapter jack and the black cable to the reset capacitor were bad, which caused crashes and much noise. Even after fixing this, it made unpleasant scratchy (walkie-talkie-like) distortions, causing colourless hissy percussion and grainy envelope behaviour (particularly at low volume). It turned out that the power amp was oscillating; after taming it with a capacitor the sound got much better. The percussion sounds less muffled than in MC2200.

    Unlike MC2200, all main voice preset sounds work properly and don't refuse polyphonic play - even the fast play polyphony  flaw is gone here because this keyboard does not mute the earliest note but ignores later notes when more than 2 keys are pressed. But long decay envelopes sound much shorter (1s instead of 2.5s e.g. in 'cowbell' or held 'piano' notes) due to changed components in the analogue RC circuit; short envelopes are not affected but even seem to be here a tiny bit longer.

    The monophonic rhythms make no use of the 'cymbal' sound and thus consist (like with the MC2200) of only 3 low- res percussion samples with audible start and end click, which gives them a fat trashy timbre and is well suited to synchronize brain waves for meditative musics. The cymbal can be only played by its drumpad. Unlike MC2200 there is a real rhythm "start/stop" button, so it can start them without beginning in accompaniment mode.

    The chord sequencer is a bit awkward to use and was hard to figure out without a manual. To program it, select the desired rhythm and press "program", which begins the synchro start mode of the single finger accompaniment ("power" LED flashes => rhythm starts after any accompaniment section key press). Now repeat in a loop until all chords are entered:

    Press "program" again to end. Press "1 beat" or "1 bar" to playback the chord sequence. You can now play a monophonic melody on the entire keyboard length while the sequencer repeats the entered chords in a loop. (The chord sequence always plays the rhythm it was recorded with; you can not choose a different rhythm later.)

    The demo "Brother John" is arranged exactly like that song of MC2200, but plays a little bit (less than 1 tempo step) slower.
     

    circuit bending details

    The Bontempi ES 3000 is based on the single-chip CPU "SC-MC-21", which controls the percussion IC "82100".

    percussion IC
    The CPU outputs 2 squarewave sound channels and trigger pulses for envelope and 3 percussion samples of the percussion IC. Additionally it outputs  plain squarewave accompaniment through 3 pins. The PCBs look like assembled in a sweatshop, so the crooked diodes and wire bridges protrude so high that they short easily. Also an electrolytic capacitor has crush dents.

    The hardware is very similar like Elite MC2200 (CPU "SC-MC-22") and mainly differs in the CPU software. So the envelope control is fully identical (see here), except that in SC-MC-21 hi octave preset sounds don't turn monophonic. The reason for the shorter decay are different components in the analogue RC network that controls the VCA.

    improve volume control

    The volume control slide switch simulates a potentiometer by a chain of 4 resistors (each 1k, located near the power supply jack). Unfortunately their values are a poor choice, so it yells terribly loud. To turn it down, connect a trimmer (I used 10k) from the right end of R11 (2nd resistor) to GND (e.g. left pin of upper resistor) and adjust it until the lowest volume setting is pleasant to use. (You may instead replace it with a real potentiometer if you like.)

    remove amp distortion

    My ES 3000 sounded very harsh and scratchy; particularly at low volume envelopes got crunchy and percussion way too thin and hissy. An oscilloscope revealed that the feeble power amp IC (a tiny TBA820M) was oscillating, sending much HF dirt to the speaker. To fix this, simply wire a capacitor from its pin 1 to pin 8. I found a ceramic 390pF parallel with 470pF sounding best, but a anything about 1nF should work. Bigger capacitors seem to worsen the timbre again; apparently it has to be tuned to cancel the oscillation wave exactly to not affect the sound.

    keyboard matrix

    Compared with Elite MC2200 (CPU "SC-MC-22"), the keyboard matrix for this shorter keyboard has a row less. The benefit of this may be that the absence of 7 highest note keys or the omitted keyboard matrix out pin 35 has freed enough computing time to play also hi octave preset sounds duophonic. Interesting is that all keys with same notes are in the same places like in SC-MC-22. Like SC-MC-2, the keyboard matrix inputs need unusually low resistance (below 1k) to respond.
     
    38
    39
    40
    41
    34
     
    CPU pin
    out 1
    out 2
    out 3
    out 4
    out 5
    in / out
     
    P.
    base
    o
    C2
    o
    C3
    o
    C4
    enter
    in 1
    13
    P.
    snare
    o
    C#2
    o
    C#3
    o
    C#4
    chord
    in 2
    14
    P.
    clave
    o
    D2
    o
    D3
    o
    D4
    S.
    program
    in 3
    15
    P.
    cymbal
    o
    D#2
    o
    D#3
    o
    D#4
    S-
    play 1 bar
    in 4
    16
    -
    o
    E2
    o
    E3
    o
    E4
    S-
    play 1 beat
    in 5
    30
    o
    F1
    o
    F2
    o
    F3
    o
    F4
    demo
    in 6
    31
    o
    F#1
    o
    F#2
    o
    F#3
    o
    F#4
    start/stop
    in 7
    32
    o
    G1
    o
    G2
    o
    G3
    o
    G4
    -
    in 8
    33
    o
    G#1
    o
    G#2
    o
    G#3
    o
    '1'
    tempo
    -
    in 9
    26
    o
    A1
    o
    A2
    o
    A3
    o
    '2'
    tempo
    +
    in 10
    27
    o
    A#1
    o
    A#2
    o
    A#3
    o
    '3'
    -
    in 11
    28
    o
    B1
    o
    B2
    o
    B3
    o
    '4'
    -
    in 12
    29

    The input lines are active-low, i.e. react on GND. Any functions can be triggered by a non- locking switch in series to a diode from one "in" to one "out" pin.
     

    legend:
    "o"
    		 = keyboard key
    S.
    		 = chord sequencer
    P.
    		 = drumpad
    orange
    background     		 = easteregg (unconnected feature)

    Place 33->34 does nothing (no button click) but blocks the panel buttons. Places 28->34, 29->34, 30->38 do nothing at all (no fixed diode). So the only eastereggs are 2 higher note keys.

    Regarding the CPU type label, also a instrument named "MC-21" may exist, which appears to be the genuine name of this hardware class. A very similar but more versatile 49 midsize keys instrument (with many rhythms and demo melodies) was released as Elite MC2200; unfortunately it suffers of annoying polyphony bugs.
     
     
    A keyboard with case like ES 3000 but very different hardware was released as Thompsonic TS-123, which is basically a My Music Center variant with changed controls (8 preset sounds & rhythms cycled through by each 2 buttons, 6 demos, sustain button, volume +/- buttons, record & playback sequencer, drumpads switchable to animal voices). It was also shown as MC-23 on the Medeli website of 2001.
     

    The Thompsonic TS-123 CPU is "31-1145-0, C2A" (26 pin DIL-shaped COB).

    Thompsonic TS-37

    Also this midsize keyboard from 1994 (embossed case date) is based on Bontempi ES 3000 hardware.

    Through its 2 bigger internal speakers the percussion samples sound quite fat and end with a strange bassy pop noise. Unlike ES 3000 it has an additional headphone and microphone jack.
    My TS-37 came with the wrong manual of MC-73, which hints that both were made in the same factory.
    Percussion samples are on a separate COB IC.
    The CPU of mine is "SC-MC-21, 3292357, Japan" (42 pin DIL) and the percussion COB module "82100".
     

     removal of these screws voids warranty...    
    WarrantyVoid
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