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Digital delay design

10/19/2000 4:01 AM
Benjamin Kunkle
Digital delay design
I need to build a digital delay pedal for a major school project. This HAS to be done so cost is not a factor. If any one can help us out, specifically with the memory block and time delay control, we would be grateful. Thanks in advance.
10/19/2000 2:57 PM
Mark Hammer

Both Holtek and Mitsubishi make digital delay chips that have a lot of the requisite circuitry on-board. In fact the Holtek HT8960 went a step past the HT8955 and stuck 20k of RAM on board the chip itself.  
While this makes design of the device a lot simpler, it may be less than what is desired by your instructor (who may want you to have to deal with addressing issues, handshaking, etc.). In any event, a search of their respective sites should provide you with links to relevant chips.  
I bought some HT8955's (capable of up to 800msec delay at 10 or 12-bit resolution) in April for about $5 US@ from Radio Shack. Try their web-site. Be prepared for them not to have stock though, since the chip has been discontinued.
10/19/2000 3:32 PM
Ed Rembold

The mitsubishi website has great app notes for  
their chips, just dig. you can build a delay just  
from those notes.  
Ed R.
10/19/2000 7:28 PM
Don Symes

If you're up for somethigng a little more exotic (how much time do you have?), there's a datasheet with code examples for a DSP up on the OEI site.  
Maybe a bit more than you want to chew right now, though.
10/20/2000 2:04 AM

I built a digital delay pedal for my Senior Design project in college. It kind of worked. You could tell that the signal was being delayed through the thick mask of noise. I used a big 'ol ram chip,1M, I think, 16 bit D/A and A/D, a 44KHz oscillator, a couple of trascievers and a bunch of flip flops to implement a state table to translate delay times. I wish I would have spent more time on it. I had it all figured out as to how I could make it do a fancy reverse mode that I still haven't heard anyone else do. Maybe someday.  
I can try to lend some advice (this was a three years ago, though).  
10/24/2000 4:15 AM

If you want i've got a copy of a pedal I made which is had delay, flange, chorus and echo all in the one unit. Uses an MN3007 (from memory).  
I can scan it in if you're interested. Came from Electronic australia magazine around 15 years ago  
Don't use the pedal too much, but it was fun making it. Also costs a bit to make too (about $100 from memory, the chip itself was $25 alone).  
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