[sdiy] re: interesting digital circuits

[tuj at fuse.net]

Well, I'm thinking about building a digital delay.  I'm looking at using a BS616LV1622 SRAM chip.  Its 1MBx16 bits or 2MBx8 bits, switchable.  Seems like that should give me about 48 seconds of mono delay, or about 24 seconds of stereo delay.

Does anyone have any other RAM chips that they like?  I'm certainly no expert.  Is there a recommended memory controller chip?

Maybe I'm missing something, but this seems relatively straight-foward.  Store a write address and a read address in two counters.  Set up the counters to wrap at the end of the address range.  Initialize the counters a certain range apart to set the delay time (probably at 0x0 and 0xMAX).  Increment the counters on a clock osc, set at 44.1kHz should yield CD quality sound.  varying the speed of the osc. should be an easy way to increase/decrease delay time.  Each clock reads the memory location, sends value to DAC, reads current value at the ADC and writes it to memory.  

Thoughts?  Is there a need for the reads/writes to be buffered?  I've also thought about incorporating two shift registers, so that on a write, the existing value in memory, and the new value from the ADC will each go into a shift register, shift one bit right, then both shift registers feed an adder, which yields the result to put back in memory.  Number of "repeats" could be controls by the magnitude of the right shift on the value coming out of memory.

Anyone actually done this?  Any advice would be appreciated.  Thanks!

-tuj