[sdiy] learning from early drum machines?

[Florian Anwander]

Hi Scott

> The DR-55 seems like a better design to me.  
yep, the TC5501 is a nice SRAM chip for drummachines because it provides 
separate DATA-IN and DATA-OUT, because you can rewrite a single 
bit(=single instrument) of the half byte, by feeding back the data-out 
of the other tracks to the data-in (see 
http://fa.utfs.org/diy/boss_dr55/dr55_schematic.jpg). This is not 
possible with the usual SRAMs with combined data-in/out port.

But unfortunately the chip is out of production. I got 7 pieces here in 
germany from a rare-semiconductors-dealer, and those were the last ones 
I found.

Florian