bartleby wrote:btw are there any known mods to allow more than just 2 samples/wavetables? perhaps by mounting 2 memory chips piggyback with a switch?
to answer my own question: yes, in fact it does work that way, and it's a pretty simple mod. i just completed it on my a112 and now i have 2 banks of 2 samples/wavetables instead of just 1.
basically what you do ist mount two memory chips on top of each other, connecting all their pins except for the two 'chip enable' pins ce1 (pin number 22) and ce2 (pin number 30). those two pairs of ce pins you connect to a 2x2 switch to toggle between the two memory chips - i.e. select which of the two chips has both its ce pins set to 'active'.
ce1/pin22 is active when connected to gnd, ce2/pin30 is active when connected to +5v.
in addition, you have to connect each of those 4 ce pins via a 100k pull-up/pull-down resistor to gnd (ce2/pin30) or to +5v (ce1/pin22), so that they aren't just floating when not set to 'active'. (thanks to dieter doepfer for pointing this out to me)
so, if you want to try this yourself, here is what you need:
2x 128kx8 cmos sram memory chip
4x 100k resistor
1x 2x2 toggle switch (like this one
the original sram chip on my a112 is called BS62LV1027PIP55, but dieter told me that these chips go by many different names such as SM621008LLP70, LP621024, 62LV1027PCB-70
(this is the one i used for this mod - thanks once more to dieter for pointing it out). for further details see the BS62LV1027 data sheet
i was going to post some pics of my modded a112, but somehow i can't seem upload them. :(
oh well, they are not that pretty anyway - my wiring isn't very elegant because i first forgot about those pull-up/pull-down connections for setting the inactive chip to 'inactive' and had to add them later. bit of a mess, to be honest, but it does work just fine.