TR-505 => TR-808?

[Byron G. Jacquot]

>	Imagine it - a TR-505 with a TR-808 bass kick.  Perhaps even with the
>eventual decay mod - wow!  The TR-505 has a great little sequencer, and
>it runs happily on six double-a batteries.  Battlestations!

That sounds like it would be a real killer...

But I suspect it might not be quite so simple to add the 808 kick circuit to
the 505.  The 808 circuit is pretty easily clone-able, and there are a
couple of folks on the list who have built their own.

The hard part will be getting anything out of the 505 to trigger with!  If I
recall correctly, the 505's digital guts exist within a few chips...probably
a microcontroller, the LCD controller chip, plus the ASIC that plays the
sounds, and some incidental logic chips between them.

If you're lucky, there will be a line in there that is being used to trigger
the kick, probably between the microcontroller and the ASIC.

However, it's probably not so simple...the ASIC probably sits in the address
space of the micro, where it's treated like a section of memory.  That would
be a nightmare to reverse-engineer, to try and discover the conditions that
apply when the kick drum is sounded.

You'll probably need a schematic to make any sense of it!  If you need help
with that analysis, you know where to find us.

If you're happy with a less elegant solution (depending on your definition
of elegant), you might be able to extract a trigger from one of the audio
outputs with a comparator or schmitt-trigger.  (and if you could find a 626
or 707, they would work better for that, because you could steal a single
voice's output for the trigger extraction.  With the 505, you're stuck with
the stereo outs, I think).

Byron Jacquot