Casio HT-3000

Casio HT-3000 Image

The Casio HT and HZ series are a very interesting group of synthesizers produced from 1987-1991. They use a very specific form of sound generation called "SD Synthesis". Short for "Spectrum Dynamic" SD Synthesis has some things in common with the subtractive synthesis we know and love. The synth takes a waveform and runs it through a real analog VCF (filter). There are ADSR envelopes for the DCA and VCF that shape the sound. And there is an LFO just like on a standard subtractive synth, although this LFO only modulates pitch (vibrato) and volume (tremolo).

Where things get interesting however, is in the choice of waveforms available from the synth engine. There are 32 incredibly varied waveforms, some sound very nasal or narrow, some like saw or square waveforms, some with an odd metallic timbre, and some feature white noise. It's still a mystery exactly how these waves are created, but experts suggest they contain a number of harmonically-rich pulse waves at different octaves, as well as a ring modulator and an analog noise source.

To make things even more interesting, these waves have pre-programmed amounts of PWM and amplitude modulation built into them. For example, one SD wave could contain two pulse waves fading in and out at different times. But you don't have to understand all of this to get the best out of the synth. The mystery and modulation of it all means you can just pick a preset and change the waves around and see what happens. The synth sounds are in the same ballpark as other DCO-synths of the time, and can even sound a little PPG-like on a good day. The filter is a bit weak for bass but adds a nice swoosh to some sounds. There is also a nice chorus effect on board. Additionally, being a home keyboard, it has built-in speakers, a Drum Machine and an Auto-Accompaniment mode (the lower tone is used for accompaniment). The drum sounds resemble the Casio RZ-1 8-bit drum machine.

The low point of the synth is in the programming. You have one big clunky rotary dial and a list of two digit parameters to edit (e.g.: 10 will be cutoff, 11 is resonance) and these parameters are not listed on the panel, so you need the manual with you at all times! MIDI is present, but limited to just 3-channels and has no SysEx support. Kind of a bummer from a synth with such a tedious programming interface.

The HT-3000 has several brothers (also released in 1987). They include the HT-700, which has 49 mini-keys instead of the 3000's 61 full-size keys. It also has a big brother in the HT-6000, which is a 4 DCO, 8 VCF and 64 waveform monster! (And the HT-6000 lists the edit parameter codes on front-panel.) Now, as no one really knows about the HT-series, they go for very little money and can be a great tool in your synth arsenal for unusual sounds!

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25 Visitor comments
February 7, 2012 @ 12:37 am
I still have the HT 3000 I bought in 1991 or 1992 I think. Works as new.
January 19, 2012 @ 8:14 pm
Ive got a HZ-600 and found it useless for retaining sounds even with fresh batteries in. The whole range has no permanent RAM. Fortunately I found a RAM card on Ebay, which turned the thing into a hybrid analogue filter/DCO synth close to a Korg Poly800 i.e. one filter divided between 8 notes. Just a shame theres no "octave down" button. This could create good basslines. Handy tip plug the midi in to the midi out for neat "doubling" effects! - obvlously you can't sequence the thing, but hey!
December 31, 2011 @ 2:38 am
I had the same problem - it turned out that a Zener diode somewhere on the brown pcb was defective. I replaced it with a standard 5V Zener and it works now. I can save my sounds to last as long as I keep the batteries fresh.
senor v
November 7, 2011 @ 4:56 pm
Well, mine is most certainly broken. I put new batteries in it AND I plug it into the wall and all my saved sounds are lost within minutes of turning it off. So, guess it'll go back onto eBay. :( Goodbye little synth.
November 6, 2011 @ 2:45 pm
A fun, cheap synth. I changed the rotary dial out for a smaller basic knob and it's much easier to do filter sweeps now. Power jack on mine died, but the batteries still work. Mine's the 700 and it has that awful Casio habit of turning off on it's own if it's not getting attention. The waveforms are what keep it interesting. Don't pay too much though.
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Rated 3.45 (148 Votes)

  • Check Price
  • The link above will take you to an eBay search for this synth to see active listings. If you don't find it there, try looking in our forum marketplace or post a wanted classified.
  • Specifications
  • Polyphony - 8 voices
  • Multitimbral - 3 parts: Upper tone, Lower tone, Drums
  • Oscillators - 1 DCO
  • Waveforms - Upper tone: 32 SD waves, Lower Tone: 16 SD waves, Noise generator
  • LFO - 1 LFO with 5 waveforms for the Upper Tone, 1 for the Lower tone. Modulates volume or pitch only.
  • Filter - 1 VCF resonant analog lowpass with ADSR envelope
  • Envelope - 1 DCA with ADSR envelope
  • Effects - Analog Chorus (3 types)
  • Patterns - Drums/accompaniment: 10 user patterns
  • Keyboard - 61 keys (no velocity). Mod and pitch wheels.
  • Memory - 30 preset, 30 user
  • Control - MIDI In/Out/Thru (3 channels only and no SysEx)
  • Date Produced - 1987 - 1991
  • Resources & Credits
  • Review by Alex Juno

    Original images from this site

    Reviewed September 2011

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