... a few comments have been turning over and over in the murky depths of my mind. Combined with the potent fuel that is Badger Tanglefoot, they've finally fired a spark across a synapse or two, and I had an idea. I'm not sure it's a very good idea (you know in cartoons a lightbulb appears above a character's head? Well there's this lightbulb but it's all dim and flickery and going bzzzt bzzt bzzzzt) but I'll share it anyway.
Bendable drum machines aren't exactly uncommon. The bits inside them are, though. If you fry the big custom chips inside, you're hosed. No replacements, no spec, no manuals, that's it. Mask-programmed chips too usually, so you can't even burn a replacement onto an EPROM without the factory firmware. Sample ROMs and firmware ROMs are easy, but not programmable logic (like the timer/counter/accumulator chip in my late lamented TR626).
So - we have some nice old drum machines getting hacked about and quite often broken. Not really a sustainable state of affairs, is it? I'd like to offer a solution to this.
How about a simple MIDI sound module, available as a bare board that you can case up yourself, which takes an EPROM full of 8-bit samples and plays them back. That's it. You can set the tuning, but that's your lot. If you feel inclined you could build an output demultiplexer and get individual outs, possibly with their own volume controls. Think in terms of a 27C512 EPROM with eight samples, each 8k long, playing back at maybe 22kHz (maybe less, depending on CPU horsepower).
I reckon I could make a PCB which you'd assemble yourself, with the complete kit price coming in about 40-50 quid. Obviously I'd be publishing the PCB layout and firmware source under a suitable licence (GPL firmware, something similar for HW design), but if I sold even ten kits at 50 quid then I'd have more-or-less made back the time I expect it would take to design and prototype.
Thoughts, objections, or anything else, please.
Oh, and you'll need to at least know more than how to change the fuse in a 13A plug. Sorry, that's just how it is.
That a great idea, but even better if you could use muliple EPROM's in ZIF sockets if you chose to, with actual circuitboard traces running to solder padss for bending points, so you could wire up a patchbay or switches easily.
Or maybe that would be defeating the object of circuitbending................... hmmm.
I'm liking the 'building block' theme though, i.e. just using it as a basic midi controlled sample playback device which you can build other stuff onto if you need too.
That a great idea, but even better if you could use muliple EPROM's in ZIF sockets if you chose to, with actual circuitboard traces running to solder padss for bending points, so you could wire up a patchbay or switches easily.
That was pretty much what I had in mind - a bunch of in-line headers or pads that you can solder some leads to, so you can stay away from the chip pins.
Another key aspect of it is that for convenience sake (mine and yours), I'd want to use through-hole components where possible. This does limit the size of MCU and ROM you can use, but does mean that any part (particularly the address latches) can be socketed, making it easy to repair when you blow it up. Of course the choice of components means that it will probably be fairly tough anyway...
Funnily enough, if you look in this months Everyday & Practical electronics magazine, there is a design for a Midi sound module that you can burn your own eeprom with .wav files for a simple wavetable sounds. Just a couple of PIC's and an EEprom. Worth the £3.75 to buy the magazine just to look at that.. You could fill the EEPROM with Speak and Spell .wavs..
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