lookmumnocomputer

CEM 3320 Gameboy megamachine findings

Added 2019-12-13 14:26:20 +0000 UTC

hello! so here we go. after a couple of days of fiddling and thinking. this is where I am at. I will (hopefully tonight) adjust the schematic for a more modular suited design, as right now its bloated with gameboy megamachine connectivity features and can seem more complicated than it actually is.

but attached is the schematic and also the kicad file of the schematic and when I make a modular specific schematic ill also share that, and hopefully down the line a strip board one too!

it sounds good. resonance can be a bit much in some settings however In the modular version ill tweak that a bit. in the schematic the chips cv input is actually inverted so if you send in 12v into the voltage divider then into the chip, it will be closed, pull it down and it will be open. I guess this was to reduces the amount of opamps used in designs, as you just need 1 inverting mixer to mix all of the cv's together, who knows.

the 4066 analog switches switch all of the various amounts, and you can actually get a couple of different low passes, and band passes if you change up what is on at what time. but for simplicity I've kept it to just 3 in my design. being :-

LPF A(on) B (on) C(off) D(off)

BPF A(on) B (off) C(on) D(on)

HPF A(off) B (off) C(off) D(on)

the A and the B actually have multiple switches within them. cross reference the schematic with both the CEM3320 data sheet and also the electric druid info on it!

https://electricdruid.net/cem3320-filter-designs/

http://www.bustedgear.com/images/datasheets/CEM3320.pdf

Im not gunna be publishing anything on this chip until I have made the video about it all! hopefully ill have this part wrapped up before Crimbo !

link to the kicad file :-

https://www.dropbox.com/sh/ht7cttggxvh8b9e/AACaY-riC5IvJN7gocUsmCgZa?dl=0