Saturday, April 11, 2009


yeah, i should really think up a better name for this design.any ideas?
first step: gather toys and parts
glitch circuit. this is not the actual toy that i used but it is similar. the glitch comes from shorting the clock speed resistor. the reset is a normally on tactile switch that disconnects the power to the circuit when pressed. the pitchbend is a 10k pot with the outer lugs connected to ground via 10k resistor and to vcc via 27k resistor.

the circuit is too large to fit into the keyboard so i consolidate the circuit and cut it down to a more reasonable size.

the drum circuit is pretty generic. i found two boxes of 12 at an outlet store and bought them all.

this circuit can be found in many different drum toys, but these are much smaller in size making them easier to work with. the pitch bend is the other 10k pot on the joysick with a 15k to ground and a 22k to vcc. the npn transistor on the left used to drive an led. i used this point to trigger the keyboard.

the keyboard is a super cheap toy! the plastic is very thin and sensitive to heat. when hotgluing everything together, i have to keep the plastic cool by blowing it with my airbrush until the glue is cooled. on the other hand, this plastic is extremely easy to cut with an exacto knife. this makes cutting the faceplate section out a breeze.

the circuit in the keyboard is unimpressive. there are no components whatsoever. the circuit loses power when you hit the keys and it sort of detunes the note maybe to get more of a piano envelope or something. there is a demo mode, but i left thos out of the interface. the 8 notes activate by connecting them to vcc. i cut the connection from the vcc to the keys and rerouted them to the drum circuit's LED output. this way the keys will only be triggered if the drums are played. also, the keyboard output is fed to the base of the drum circuit's output transistor. this gets rid of that bad "piano" envelope and the keyboard audio is modulated by the drum sounds making it sound all "8-bit".

in order to use the drum and glitch circuit, i utilize the the unused black keys. for this i have to add a small circuit board.

the 4 switches to the left will activate the drum sounds and, and the one to the right will sound the glitch circuit(carhorn). the 3 drum switches to the left play drum sounds and 3 different rhythms when the rhythm is playing. there is also a 4 position slide switch that will hold the rhythm continuously. the 4th switch to the left is the rhythm start/stop switch.

the joystick is just a run of the mill game controller joystick. i found some little plastic beads and drilled tiny holes into them to replace the big hemispherical caps that were originally on them. i also took the joysticks apart and removed the spring the holds the stick in the middle. this way the stick will stay where ever you leave it.

putting it all together is pretty easy as long as everything is working properly(and you used a 15k not a 51k resistor). after about the 5th time building one of these, it comes together pretty fast. i finished the last of 3 today. from start to finish it took about 2 hours.

since there is not a lot of room in these, i like to keep the wires as short as possible. here are some peeks into the inside of a finished one.

and the finished product

each one of these is slightly different. the one with the blue joystick's audio is mixed differently that the other two, and the one on the bottom has the line out in front of the keyboard(thats because i'm an idiot). to hear these 3 in action, watch this video.


while i was waiting for the paint to dry on my casio pt-100, i threw this together. its basically a new version of the holiday keyboard with the addition of a glitch circuit. watch the video...

Friday, April 10, 2009


i finished this one a couple weeks ago. i spent three weeks building it but i was too lazy to even go up stairs to get my camera, so this entry is pretty brief. i found a toy drum at the bins a while back(pre-toy crisis).

i've had a couple of these in the past, but this one was slightly different than the other two. actually the other two are a funny story. back in the earlier days of my bending career, i found one of these for a couple bucks at a thrift store and had big plans for incorporating it with a "yak-back" and some other stuff. i had it all planned out and ready to go, but then i fried it, or so i thought. in order to salvage the project, i shelled out $35 for a new one off ebay. unfortunately the new one wasnt the same. the record function only played back your rhythms as they were recorded. the old one snapped each hit to the step. also, by the time it had shipped to me, i had already lost interest in the project...ok, that wasnt a funny story at all... anyway, i found this one and quickly noticed that the 8 demo rhythms were not as realistic as the first two i had owned. they were pretty much just random sounds and orch. hits. the drum sounds themselves were pretty good though and the retriggerability is great too. i stripped the circuit down to the chip and decided to rehouse it into an old modem box i found.

each drum sound is triggerable via one of six LFOs. because the drum sounds were triggered with pressure sensitive peizos, the LFO frequency can go pretty high without causing any stuttering in the drum sounds with the exception of the kick drum which was triggered with a regular foot switch. for each of the 6 LFO's, there is a 3 position switch. each switch selects either manual(normal)trigger/LFO continuous trigger/LFO manual trigger. below each 3 position switch is a momentary push switch. with the LFO in manual(normal), the sounds will only trigger once per tap. in LFO manual, the momentary switch will enable the LFO only when the button is pushed. in LFO continuous, the button does nothing. to the right of the 6 drum sound buttons are 4 function switches. the two on the left control the tempo and the other two are for record and stop. to the left of the 6 slide pots that control the LFO's frequencies, there is a longer slide pot that is the pitch bend. at the top of the machine is the pitch mod and echo section. from right to left there are a joystick that controls the speed of the pitch bend LFO and the speed of the echo, a three position switch that changes the pitch bend LFO shape from tri to saw to rev. saw, a switch that turns the pitch bend LFO on and off, a switch that turns the echo on and off, and a pot for the number of echos. when the echo times pot is all the way up it feeds back just a little bit and can get out of control if you want it to. in the back there is a power on/off switch, a 1/4" line out, and an RCA mic in jack for the echo. i also left some room back there in case i want to add ports for external devices such as drum pads or a keypad to activate those cheesy demos, and possibly a volume pot for the mic input. the 4 leds in the front indicate from left to right, power on, echo on, pitch lfo on, and the last one blinks with the sounds and also lights up solid when recording. ok, i think thats about it. i kind of wished i had taken pictures of the inside but oh well.