MATRIXSYNTH: Casio Brochures

Friday, July 27, 2007

Casio Brochures

Title link takes you to shots of various Casiotones via this auction. Anyone know more about the 101? Analog? Digital?

7 comments:

  1. No Casios are analog Poly-Synths like Junos or such.
    All are digital, some of the earlier models with auto accompaniment use Analog drum circuitry (home organ style, an ringing oscillator and white noise shaper for each tone). They have switched capacitor filters to generate different timbres, some of the accompaniments have capacitor filters for the envelopes of the notes.

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  2. I think there were one or two early Casios that had analog filters or partially analog filters. There's one Casio that even has an input for sweeping the filter. Could all be digital though. Loscha would know better than I would. I never thought the Casios sounded analog, but they don't really sound digital either. I've got a VL-1 and an MT-40 and they both occupy their own niche in sound space. I've used the VL-1 waves as starting points for sounds on my V-Synth XT. You'd never know they started out Casio. They actually sound better than patches I made with PPG waves.

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  3. The MT-400V had an actual synth filter and a BBD chorus. The oscillators on the early Casiotones consisted of two different "wavetable" (arbitrary 16-step wave) oscillators, each with its own volume envelope. Entirely digital except for the switched "formant" filters (not all that interesting IMO) and the drum sounds. The sound is generated through a single DAC, but the sampling frequency was around 600 KHz so there is practically no aliasing.

    Here is a really good explanation (the writer actually reverse-engineered the chip in the 80s):

    http://www.firstpr.com.au/rwi/casio-keyboards/Casio-931-2006-06-17.txt

    I have an MT-100 which has to be one of my all-time favorite keyboards, especially with the unfiltered output and the alternate modulation setting switches added in. Very under-rated especially for weird thin reedy sounds. "Pipe organ" is also the best Farfisa-type sound I have heard on any keyboard ever.

    PDM

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  4. Other than the CT410V/MT400V, the Casio HT series had true analog filters in a custom chip, the NJM2090 (good luck finding the datasheet, though). It's quite a nice filter if you mod it:

    http://www.youtube.com/watch?v=BMi6kqhd_1M

    The HT's were a bit similar to entry-level DCO synths like the Korg Poly800, in that they had programmable "oscillators" (waveshape selectors) and the single filter processed all voices.

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  5. MT-400 and DH-xxx Casios had filter chips in them. The pinouts are in the service manuals, but, that's about it. They're sort of like the CEM chips I guess.

    To expand on what Anon has written here. Casio based their idea of synthesis (perfected in the MT65) on a Vowel/Consonant model. Noises like guitar, flute, xylophone, all had a linguistic peculiarity to them. A consonant sound (the attack) and a sustained vowel sound. The two parts of the waveform interact in similar ways. The static formant filter frequencies chosen in these keyboards are based on those of the human vocal tract, designed that the instruments would impart a more naturalistic perception.

    The VL-1 uses patterns of up and down waveforms, similar to Walsh Tones (as observed by Robin Whittle quite a while ago), whilst not exactly walsh tones, it is worth looking up walsh functions on wikipedia or wolfram anyway, because they're interesting, and a beautiful picture to look at).

    The MT45/MT11 uses a different type all together, instead of using a 12 bit DAC, it uses 2 differently weighted bits (1 and 64) added together to make sounds.

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  6. Hi Loscha.

    No custom filter chips in my DH100 - just a funky 4-pole analog filter using 4 FET's as the variable resistors and two op amps as input & output buffers.

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