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MXR Digital Delay - Memory boards?

9/19/1996 11:36 AM
Mark Hammer
MXR Digital Delay - Memory boards?
This past spring I bought a late 70's (early 80's) MXR Digital Delay unit;  
the rack-mount one with the row of pushbuttons to set delay range. I didn't get  
a manual with it, but was able to deduce enough from the my background knowledge  
and a very thorough review and block diagram in an old issue of DEVICE magazine  
(Craig Anderton's long-defunct electronic guitarist newsletter; I have all known issues).  
As a chorus, it's good. As a delay-line, it's pretty utilitarian. As a flanger, well, let's just say that the modulation capabilities aren't up to  
what a decent flanger needs, although the remote sweep pedal is a nice touch.  
From my understanding, the maximum delay range can be upped by plugging  
additional memory boards into the expansion bus inside. The only source of said  
boards that I've ever heard of is Analog Mike who sells them for $75 a pop...  
when they can be found. Given that it would probably cost about another  
$225 to produce the same delay time (1280ms) that can be bought in a more recent  
box for less than that (and at higher resolution, too), I'm naturally quite  
reluctant to go the OEM-board route. Ideally, I'd like to wire-wrap some  
expansion boards of my own but I have absolutely no idea of what the  
board/bus architecture is. The memory board in there has big clunker  
ceramic RAM chips with absolutely NO markings on them (not even a house  
number), and the number of chips and delay time gives me no clues as to what  
the plausible candidates for substitutes are. I've tried calculating byte-size  
by delay-time by sampling rate, and comparing it with architecture of known  
DRAM's or SRAM's but nothing seems to add up, so I'm stymied and stuck at  
320ms of delay.  
Any, and I mean ANY, info that could let me figure out what I would need to  
make use of the expansion bus would be greatly appreciated. Hell, if it  
doesn't take much out my time and I have any RAM left over, I might make one for  
for you.  
Thanks for whatever you can do for me, Mark Hammer

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