Roland TR-808 Modded by Robin Whittle

images via this auction, via Gustavo.
"Robin Whittle modifications / extra features :
1. In addition to the original memory, two banks of 10 memory units
(ie. 20 times the original memory).
2. 4 levels of volume accent (rather than the original 2) each one with volume control giving you much more dynamic feel. There are LED's that flash during playback to indicate what accents apply to each beat.
3. Individual tone control for both the toms and the hand clap. This means you can vary the toms from being a dull thump to a sharp crackle.
4. Three phono jack sound inputs to replace the sound generators for the toms, white noise and the cymbals. The drum settings for these channels act as a gate for the input sound so for instance, you could feed in another sound such as a sound effect, musical chord or voices and program the 808 instrument to gate that incoming sound. There is some post filtering so the input sound takes on some of the drum's original character.
5. 3 x trim pots for adjusting the pitch of toms, white noise and cymbals.
6. Multipin input for a touch sensitive drum pad set to drive the 808's sounds manually. (pads not included).
6. Individual damper switches for the three toms - left = short, right = long.
7. Soft reset button - resets the computer without the need to power the whole machine down.
8. Two more toggle switches that I can't remember the function for.
Though there was no instruction manual for the Robin Whittle mods, I have prepared some illustrated notes to help you get the most out of this 808.

It is otherwise as manufactured, and has not been MIDI retrofitted. If you wanted this feature, I believe it can be done reasonably easily and I found this URL for an 808 MIDI retrofit that looks very well priced ... and also another one in England."