Super Stereo, My Portable Rockman

Super Stereo

sound toy with rhythm loops, piano and animal samples

My Portable Rockman

Super Stereo

This sound toy has an almost empty green/ red plastic case in the shape of a small ghettoblaster. It has a white silicone (rubber) keypad and plays many rhythms and sounds. At the front is a green pseudo "CD lid" with the label "dynamic sound"; behind it was a deck of tiny picture cards for children. It plays preset rhythms, animal samples, piano sound and melodies. All sounds are made from lowres samples.

main features:

lousy silicone keypad with 16 small buttons
8 buttons for piano keys, switchable to OBS demo melodies
tiny plastic loudsqueaker
8 preset rhythms
8 short monophonic piano melodies
7 low-res percussion/ animal samples
3 animal sound buttons {dog, frog, bird}
4 drumpad buttons {low woodblock, high woodblock, laser, whistle}
on/off button switches to rhythm mode
flashing lightbulbs

modifications:

cinch sound output, speaker mute switch and AC adapter jack with regulator added.
speaker replaced against a real one. (I toasted the headphone- like original plastic squeaker when I halted the CPU clock.)
pots for volume control, distortion, pitch (CPU clock) and click effect (from lamp output) added.
reset (rhythm stop) button added.
8 switch DIP switch block + enable switch added to permanently select a rhythm pattern. (Rhythm otherwise falls back to default when a button is not held down.)
"drumroll" pot added.

notes:

The piano sound uses a very coarse piano waveform sample with envelope.

In rhythm mode a standard rhythm pattern is running continuously and any press of a "drum" or "animal" button plays 1x an alternate rhythm pattern depending on the pressed button. All alternate rhythms and demo melodies play in a loop when their button is held down.

circuit bending details

This was one of the first instruments I had modded. I had done here quite traditional circuit bending, that has nothing to do with (anyway absent) matrix eastereggs.

Danger: The conductive layer of these silicone buttons is extremely thin, though by the abrasion of multiple assemble and dismantle cycles and my attempts to clean the badly working contacts (by rubbing etc.) I finally destroyed the layer completely (Arrg! 8-[ ). In the shop where I once had bought the toy, they only had left a single, bleached out specimen with broken "CD" lid. Fortunately I managed to transplant its silicone keypad to my circuit- bent instrument. Halting the CPU clock will fry the plastic loudspeaker.

All buttons are sensed by 6 lines those react on VCC (=+4. 5V). Instead of a matrix, this awful hardware senses combinations of multiple simultaneous input lines pulled to VCC as different key inputs, though each rubber key presses against multiple contacts, i.e. when a key is pressed too weakly (or contacts are dirty), the wrong(!) sound is played. (This kind of keyboard hardware seems to be also quite common in toy mobile phones.)

For the 8 DIP switch block I had to wirewrap a bundle of very thin wires to the fragile PCB without destroying the tiny, tinned PCB contacts for the silicone buttons. Due to the buttons respond bad (wrong sounds) I tried to solder some diodes on the tiny PCB to remove the need of connecting multiple contacts for each button, but it hadn't much success (possibly due to the voltage drop of diodes.

I added a "drumroll" pot, which makes a feedback from the lamp output to the DIP switch with an electrolytic cap and though re-triggers a pattern again and again with each n-th flash by simulating fast button presses. (This function behaves a bit unpredictable when other pots are turned, but this makes it also interesting for experimental music.). I added a click effect pot from a lamp output; it is routed through a DIP switch to avoid distortion when off.

The resulting instrument can make quite versatile, grainy tekkno rhythms, and the sound CPU can be ridiculously overclocked without crashing until the rhythm turns into a continuous beep. Never the less I added an opener button switch in the CPU supply voltage as reset to stop rhythm.

My Portable Rockman

The same sound CPU is also used in the walkman shaped sound toy "My Portable Rockman", but this one has the key buttons placed in random order (no continuous tone scale), which makes it extremely difficult to play melodies without modification.

*removal of these screws voids warranty...*

	back