He all, I'm trying to find some information on the design of analogue delays. I want to understand better the sections of them and what they're there for.
I've found a few bits of info on them, but nothing that detailed. Does anyone know any books or sites that have detailed descriptions, like block diagrams and technical information and such?
Quote from: daverdave on December 31, 2008, 01:32:15 PM
He all, I'm trying to find some information on the design of analogue delays. I want to understand better the sections of them and what they're there for.
I've found a few bits of info on them, but nothing that detailed. Does anyone know any books or sites that have detailed descriptions, like block diagrams and technical information and such?
Have you read any of the data sheets for the bucket brigade delays? This might be your best starting point.
Read these and look at the application circuits to start:
http://www.datasheetcatalog.org/datasheet/panasonic/MN3205.pdf
http://www.datasheetcatalog.org/datasheet/panasonic/MN3101.pdf
You most likely want some kind of buffer, then split in the signal path: one side to bucket brigade delay line then filter, then summing amplifier/buffer; other side dry effect to summing amplifier/buffer.
The BBD delay chip is controlled by a clock generating chip.
Those suggestions might be too obvious, but maybe not. I think the filtering is the most complex/black art part of the design. You will most likely spend all of your effort there. I don't know if there are strict design rules to follow for the filtering but it might be one of those things you really have to play with to get the 'best' sound.
http://www.amazon.com/Audio-Users-Handbook-Circuits-Manual/dp/075063006X (http://www.amazon.com/Audio-Users-Handbook-Circuits-Manual/dp/075063006X)
This book has a chapter on delay circuits. Both analog and digital.
Thanks heaps for the replies, I'll look over those datasheets, and I'll definitely get a copy of that book.
I have found some info already but as I said not much, there was a block diagram on http://www.geocities.com/scaprile/fxa.html
I'm not sure what an antialias is though, can't seem to find much about them on the web.
Quote from: daverdave on January 01, 2009, 12:22:25 PM
Thanks heaps for the replies, I'll look over those datasheets, and I'll definitely get a copy of that book.
I have found some info already but as I said not much, there was a block diagram on http://www.geocities.com/scaprile/fxa.html
I'm not sure what an antialias is though, can't seem to find much about them on the web.
When an analogue signal is converted to the digital domain it becomes periodic with respect to the sampling frequency. Look up the wiki page on Nyquist rate etc. The anti aliasing filter is a low pass filter that blocks the un-needed high frequency content from the guitar/audio band. The sampling rate in the chip has to be at least twice the highest frequency from your anti-aliasing filter. Without the filter, your signal would get all messed up when it's sampled. The frequency content of your guitar/audio signal has a positive and sort of imaginary negative part that's a mirror image. When you sample it, the positive and negative parts show up around the sampling frequency as upper and lower sidebands. The anti-aliasing filter makes sure the upper and lower sidebands don't overlap.
That's great man, thanks. do you know any websites with info and circuit diagrams of antialiasing filters? I picked up a copy of that book, it looks really good.
This is a pretty standard university text: http://www.amazon.com/Signals-Systems-Prentice-Hall-Signal-Processing/dp/0138147574
Might be a bit math-y. No circuits in there. For this application I think you only need a low pass filter.