The OSC Toy-Box - Casio DG-20 Digital Guitar
Updated: Jun 1, 2022
So, one Friday evening my neighbour unexpectedly drops by and tells me he's having a clear-out. He says he's got an old electric guitar that doesn't work anymore and it's either going in the trash, or it's mine, if I want it (he's seen me coming and going from time to time with instruments and knows I'm a musician).
In this situation, I'll always take it, as I can probably fix it (if it's an electrical fault) and either use it in my own music or make use of it at my day job (a secondary school).
He then hands me this... 😱
This is a Casio DG-20 Digital Guitar (circa 1987). It has 20 tone presets and 12 drum patterns. It also has a drum-fill button (for adding fills to the drum patterns), as well as four individual drum sounds, should you want to throw in some random, extra drum fills of your own. It has MIDI-Out and a built-in speaker.
It's a Guitar, Jim, but not as we know it!
Whilst I'm not a great guitarist, I can play the guitar (in a rhythm-guitarist sort of a way) and own several guitars. Whilst this looks like a guitar, it doesn't really play like one. It seems Casio were attempting to corner a gap in the market in the late 80s; providing a synthesiser option for guitarists. It has a strong sense of the "experimental" about it, as if they were stretching what was technically possible at the time (with regards to touch pad technology and user interfacing). In retrospect, they were overreaching (I'll explain more below), but in 1987, when these things hit the market, they must have seemed extremely cool and futuristic.
How Does It Work
From what I can deduce, there are two main aspects to its functionality.
Firstly, you pluck a string and it registers "note-on" (in MIDI terminology), via a sensor in the string mounting in the saddle. These are sprung sensors, and the string needs to be plucked with a reasonable degree of force. Delicate or rapidly repeated plucks don't register well, if at all. But that's all this aspect of the design does! A pluck only registers "note-on"! The actual pitch of the note is determined by the second part of the design: the fretboard sensors.
The fretboard is rubber (which is a weird tactile experience in of itself). Beneath the rubber is an array of sensors (sensor board picture on the right is from this informative blog).
If none of the strings are held down (i.e. you strum an open string) it registers the open string tuning of whichever string you pluck. Each fret however has six corresponding sensors (one per string), that registers its respective note on the fretboard when pressure is applied. E.g. if you hold down the low E string on the first fret, it registers an F.
Therefore, "note-on" is registered by the string pluck and the note-value/pitch is registered by what you are (or are not) pressing on the fretboard.
The sounds are everything you would expect from a small format Casio synth of the mid-late 80s. They're crude, simple, charming, and wholly unrealistic (not that realism is really the point with this sort of an invention). There are some basic guitar-like tones, and then some other interesting patches such as organ, glockenspiel and clarinet. My personal favourites are the more pad-like and bell-like sounds; they're quite lush and warm.
The drums are equally charming, run-of-the-mill, Casio sounds from the mid 1980s. Crunchy, boxy, simplistic, but containing huge amounts of rustic, kitsch charm.
The built in speaker doesn't reproduce the highest and lowest frequencies very well, but the line-out allows you to better enjoy the full range of the frequency spectrum, in all it's crunchy, buzzy glory.
Frankly, there is none! Or at least, if you're approaching the DG-20 with any meaningful experience of playing normal guitars, this will feel very alien.
There's no velocity sensitivity; it's all or nothing. Softly plucked notes don't register. Insufficient pressure on the fretboard registers an open string. Too much pressure and you trigger vibrato ("modulation" in MIDI terms) or the string itself touches the next fret up, registering a semi-tone (half-step) sharp. Trying to be accurate on this instrument is like dancing on ice.
The strings are nylon and all the same gauge which feels unusual. It doesn't support note bending (not that bending notes is possible on the sticky, rubber fretboard). Instead you have to apply extra pressure on the fretboard to trigger vibrato, however this often unintentionally misfires (as mentioned above).
The really bizarre thing though, is that, because the strings are only registering "note-on" and the pitch is determined by the fretboard sensors, it doesn't matter what the strings are tuned to, as long as they're reasonably taut (to trigger the "note-on" sensors).
I had a really difficult time getting to grips with this at first, as the vibration of the strings was a different frequency/pitch to the note being generated. This was highly counter intuitive. Whilst the string resonance isn't audible, it can be felt in the fingers. Therefore, hearing one note and feeling another causes a viscerally dissonant sensation. It's hard to explain, but if you've spent many years playing the guitar (or any instrument for that matter), you become accustomed to the note you hear being mirrored by the tiny vibrations you feel through the instrument. For the sound and feeling to be unrelated is seriously disconcerting.
To counteract this, I tuned the strings properly to E, A, D, G, B, E. However, with the strings being all the same gauge, the lower strings were far too floppy and the higher strings were too taut. In both instances, this caused the pluck sensing to falter and become too inaccurate. I had to compromise and tune all the strings to be within the same octave. This means the low E and A are an octave higher than they should be, and the high B and E are an octave lower than they should be. All in all, a bizarre and counter intuitive experience for anyone accustomed to a normal guitar.
So What Was Broken, Leading To Your Neighbour Giving It Away?
The DG-20 either runs on a 9-volt power supply or utilises six D-Cell batteries (the really big, fat ones). I learned from this article that in order to save the user accidentally leaving it on and draining the batteries, there's a primitive "auto-off" circuit, which after six minutes of inactivity is triggered to shut down by the CPU.
It's common for some transistors in this "auto-off" circuit to fail (circled in the picture on the right). I traced voltages with a multi-meter, and the power ceased at this point, meaning I too had a fault with the "auto-off" circuit. I replaced the transistors (as I had some compatible spares), but it still didn't work. The fault therefore, must be in the capacitors that store the charge that keep the transistors open during active use. I had no spare capacitors and the capacitors on the board all looked healthy (normally failed caps have bulging tops and/or signs of leakage - like an old, expired battery).
I have no intention of using the DG-20 on battery power. It's inefficient, expensive and probably not great for the environment. I have spare 9-volt power supplies I can use to power this thing, and so I wasn't going to spend time diagnosing and shopping for capacitors, to repair a battery saving bit of circuitry I knew I would never need.
I therefore short-circuited the "in" and "out" pins on the inactive transistor, and the DG-20 came back to life.
A Little Slice Of History
I'm still a little unsure how I feel about having come into possession of an instrument such as this. I feel less like I've acquired a musical instrument and more like I've acquired a museum piece, a relic, a scientific and commercial oddity from a bygone era that literally has no place in the modern world, other than a conversation starter. It's like the Sinclair C5 or Nintendo Virtual Boy of guitars (or synths... I don't even know whether it's more guitar or synth at this point).
Casio's research and development must have undoubtedly told them it was inadequate solely as a guitar and no serious guitarist would really utilise the DG-20 due to its un-guitar-like characteristics. They must have known they were overreaching and more likely creating a toy-like tech-demo of what might be achievable in the future.
Perhaps, what it lacks in intuitive playability, Casio compensated for with a bold, futuristic design. If that's the case, they nailed it! When I posted a photo of this on my socials, it got more traction than some of my music releases got, which says a lot about about how right Casio got things on the style front (or how wrong I'm getting things on a musical front 🤣).
A Conversation Piece?
I know some people with unusual, imported cars, and every time they park up or stop for petrol, someone always approaches them and says "Hey! What is that?! Is that an import?! From Japan?!", followed by an inevitable conversation about import costs, tax, insurance, spare parts, etc. The car owner has had this same conversation many times with many strangers.
I feel like this guitar is going to play a similar role in my life. It's charmed me too much to part with and its sounds are so wonderfully kitsch, I simply have to use them in the future, but I'm probably going to spend more time admiring it and talking about it to curious houseguests and onlookers, rather than actually using it. It's possible that this was part of Casio's intention; to inspire conversation and spark imaginations about what the future of music technology could yield. Either way, as a museum piece, conversation starter or a musical instrument, owning a DG-20 in 2022 has a sense of post-modern irony about it.
Verdict: Beauty & The Beast
All things considered, it's beautiful and ugly in equal measure. It is borderline unplayable as its fundamental design was too ahead of its time and the sensor-technology is not up to the job of adequately capturing the nuances of a guitar. There's probably a knack to it, but it would require far too much time to master, and probably have limitations on what is feasibly achievable.
Sound-wise, it's arguably pretty rubbish too and not making any great impressions as a synthesiser. However, this is far more subjective than the playability. Sure, it's rubbish by modern standards, but my gosh, are the sounds fun! The tones and drum beats are dripping in nostalgic charm and I know I'm going to use them at some point.
With future use in mind, I have sampled all of the tones on the DG-20 for ease of use. You can download them here. The sampler-instruments are configured for Logic's EXS24/Sampler, but it shouldn't be too much work to load the samples into your sampler of choice as they're all individual audio files and clearly labelled.
So there we have it: the Casio DG-20. An ironic, post-modern oddity of retro aesthetic that's equal part beauty and beast.