Casio DG-20 digital guitar

[gmeredith]

I just bought one of these. Eagerly awaiting delivery. Has anyone ever bent or modded one of these? I think it lends itself very well to bending, basically being a standard cheesy casio keyboard in it. I can see already that you could do a separate drums-out socket mod on it, as it has a separate volume control for the rhythms.

Cheers, graham

[Griffin]

oooh - i think you're right. That'll be fun!

[Circuitbenders]

But will bending it stop you prancing around like a camp deviant the second you strap it on? I think not as the lure is irresistible. 

[gmeredith]

This is standard issue equipment for camp deviants, so no amount of bending will stop the prancing

Cheers, Graham

[kb]

Hmmmm...I've toyed with getting one of these for one basic reason: 

supposedlly, the synth engine of the DG-20 is the same as the HT-700.  If that's true, then the DG-20 should have, as does the rest of the HT-series, a nice little custom 4-pole analog filter chip (NJM2090) that's 'underutilized' in the stock Casio design.

You can bring out manual controls for cutoff, resonance and make some really scary and warm noises with it.  I did this to my HT and my MT600.   

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

I've even harvested the chip for installation in other keyboards - nice that it runs off 0-5V supplies!



Looking at the DG-20's manual, though, I'm not sure the chipset is identical, because there are fewer overall sounds and some different ones.  also, doesn't seem to have onboard chorus like the HT's do...

When you get the DG and crack it open, can you let us know if the DG DOES have the onboard filter chip?   

[gmeredith]

I certainly will!! If it does, I hope you'll share with us how you did the filter controls. Those filter mods you did were EXTROARDINARY! You took a cheesy casio keyboard and turned it into a Roland Juno!!. If mine has a similar synth engine to yours, I'd be very keen on modding my DG20. I'll take circuit photos as soon as I get it. I'm already planning to build into it a DOD distortion pedal and a boss stereo chorus pedal, and I don't even have it yet!

Cheers, Graham

Update: Hi KB, I think I found your HT/MT filter mod site:

http://home.earthlink.net/~kerrybradley/id7.html

Nice work!! I've been heavily modding my casio sk-8 sampler for a while now, and one of the plans I had in mind was for an add-on filter with res. The trouble has been to find a simple filter circuit that runs off +5V DC and a CV input. Pleeeease think about working on the standalone filter you mentioned you were planning to do sometime using this casio chip!!! The SK-8 is already set up to run the filter chip with an ADSR line from the processor, so I could tap that as well as use your manual controls. I could have 8-bit samples running resonance filters!!

Cheers, graham

[kb]

Hi Graham,

Yup, that's my lame-ish vanity site you've found. I'm no web designer so I just used the webtools provided by my earthlilnk acct.  Sorry that the MT filter page is incomplete - I have to get the schematics I used and some more explanatory images together and get 'em posted.

I've been tracking your SK-8 posts on electromusic and the casio board - excellent stuff!  I wanted to pick your brain about the RAM chip you added.

So, if you like, let's talk offline about the filterchip et al.   My email address is on the homepage of the ~kerrybradley acct (it's not a link, it's text-ified to avoid spam).

[Signal:Noise]

That filter mod is amazing.

[gmeredith]

The DG-20 just arrived in the mail today, WOOOOOOT!!!!

In immaculate condition! Haven't had much time to play with it though, a thing called "work" got in the way! I did do a few things, though, tightened the strings, set it up better. I must say that people such as myself who have very big hands and fingers will find the fretboard a little narrow, I often put my fat claws over more than 1 string every now and then and trigger 2 notes while doing a solo. But I'm sure I will clean up my act, I'm a bit clumsy like that on a real guitar as well (I'm a bass player, not a guitarist!).

After playing around on the preset sounds for a while - which aren't too bad at all, surprisingly - I MIDI'd it up to my TX81Z module and started doing what I actually bought it for -  play bass synth guitar. The TX excels at really fat synth bass sounds, and it sounded FANTASTIC hearing those sounds being played with a stringed instrument. I love it! It wasn't too long before synth bass lines such as Devo's "Freedom of Choice" and "Whip it" were heard emanating from the music room! A real 80's inspired piece of equipment.

I suspect that the DG-20 will lend itself very well to modding and bending. The first thing I'm going to do is permanently wire up some Ni-Cad batteries into it and install a charging socket, so I can ditch the mains adapter.

Then I'm going to put in a drums-out socket that will switch the drums out of the main out socket when you plug into the drums socket, so you can have separate outs for mixing.

On some of the presets, I have already noticed that it has 2 types of LFO's - triangle and square. The mandolin has the square wave tremolo "chopper" LFO on it's volume. The trumpet, clarinet and several others have a triangle pitch vibrato.  There is here the possibility of bending these to affect any VCF that may also be present, according to KB's post, or one installed into it.

Definitely going to build a distortion pedal into this thing! The 8 guitar sounds are clean sounds, rather than preset digital "distortion" sounds, (it does have one listed as "distortion" but it's more of a sawtooth synth wave) and should drive a pedal nicely and sound very realistic overdriven. I'll post up some mp3's when I try this. I could bring the pedal's controls out onto the DG somewhere, there's ACRES of room to add stuff.

I'm going to try to change the strings for a better feel. The DG-20 uses 6 nylon strings that are all the same thickness (about the small E string on a nylon string guitar), and you don't tune them - you just tighten them to some nominal tightness. Since the sounds are actually produced by switches under the rubber fretboard, the strings are there simply to trigger the "keys" you hold down, and to give a "guitar" type feel to the neck.

The 3 bass strings feel unnaturally thin. I'm going to try thicker nylon ones for those (don't use metal strings - they will cut the rubber fretboard and frets up - also, they may not bend enough when you press on them to trigger the fretboard switch underneath them). This will also enable me to put more tension on them so they're less bendy and sloppy feeling.

Last of all, a set of straplocks for the strap - you don't want this thing hitting the concrete!!

I'll take internal shots as soon as I get a chance to open it up. Does anyone know where I can get the service manual for this thing?

Cheers, Graham

[kb]

Signal:Noise:  thanks!  everytime I turn that MT600 on, I'm really amazed how much you can open up the sound with those filter controls.  if you can find any of those HT boards cheap, they're definitely worthwhile.



Graham:  congrats on the DG safe arrival!!  looking forward to pics of the innards! 

it rains, it pours:  matrix just put up a post on another fellow demoing his DG-20 on YouTube.  surprisingly nice instrument.

funny how so many of these old 80's Casio consumer 'toys' are getting a new life:
- bending has unveiled amazing sounds and sequences from bread and butter Casios, most of which are nominally cheesy laptop organs
- alternative controllers, like the DH and DG, are being recognized for their expressiveness (of course, without MIDI they'd really be toys...) and their prices are going up

[Signal:Noise]

Did all te casio mt-s have that filter chip? because i had an MT-55 that i modded and later sold that didn't really seem to have much, I'll be gutted if i missed this.

[gmeredith]

OK, here is some pics of the inside of my Casio DG-20.

The case opened:

[gmeredith]

The main board, track side:

[gmeredith]

Closeup of the 2 chips on the track side

:

[gmeredith]

Main board, component side: