bk@cs.brown.edu (11/11/89)
Does anyone have any experience with building simple digital effects for
audio signals. More specifically, I play guitar, and I would like to
build an effects box for my electronic guitar. Something based on delay
circuitry, with feedback loops, oscillating clock speeds, etc... Right now
I'm thinking of using a big RAM chip for the delay: feed the guitar line into
an Analog to Digital converter (AtoD), put its output into the RAM chip at an address
specified by a counter, get the contents of the RAM chip at an address which is
some variable distance "behind" the input address, and feed this value to a
Digital to Analog converter.
Is there any info out there on this? I know that there exist tons of info
on digital signal processing, but I'm only interested in this very specific
portion of it. I also don't want the design to get too complicated.
Anything would be appreciated.
--- Brian Knep uunet!brunix!bk
Brown University bk@cs.brown.edu
bk@browncs.bitnetstank@anvil.WV.TEK.COM (Stan Kalinowski) (11/15/89)
In article <20445@brunix.UUCP> bk@cs.brown.edu () writes: >Does anyone have any experience with building simple digital effects for >audio signals. More specifically, I play guitar, and I would like to >build an effects box for my electronic guitar. Something based on delay My advise to you is that such an undertaking is not worth the effort, unless, of course, your goal is to learn how to design digital signal processing systems. The days of homebrew effects boxes are numbered, the state of the art has advanced well beyond the skills and equipment of the average musician/technician. In a recent issue of Electronic Musician, Craig Anderton made this very same point, and I agree with him. (In case you didn't know Craig wrote a book about building guitar effects pedals in the 70's, I think it was titled "Electronic Projects For Musicians", it was once very popular and may be out of print now.) Craig's point in the EM article was that homebrew pedals made sense when the quality of the commercially available pedals was poor and they were costly, but the new designs are very reliable and very often cost less than the price of the parts you would have to buy if you built it yourself. You should also consider that most digital effects boxes use a specialized DSP processor chip, so if you wanted to "roll your own", you would likely need access to a software development environment for the DSP processor. Having said all that, I don't want to discourage you from trying to build a simple digital delay yourself. I simply suggest that you examine your goals before doing so. If you want to learn, then it would be a worthwhile project, but if you want to save money, then don't bother, your time would be better spent shopping around for the best price on a used digital delay. By the way, if you do want to get into digital signal processing, I would recommend getting access to a computer that has the hardware already (like the NeXt box), and concentrate on learning how to program the DSP processor. The software is the really interesting part, the conversion hardware is not very exciting, technically. stank US Mail: Stan Kalinowski, Tektronix, Inc., Interactive Technologies Division PO Box 1000, MS 61-028, Wilsonville OR 97070 Phone:(503)-685-2458 e-mail: {ucbvax,decvax,allegra,uw-beaver}!tektronix!orca!stank or stank@orca.WV.TEK.COM