[sdiy] 4xD Quad Flanging Delay - PCB orders

[Seb Francis]

Hi,

http://burnit.co.uk/sdiy/index.php?page=4xd

The 4xD PCB design is now finished and ready to be ordered.  I had a few 
requests for supplying some of the parts, and a couple of requests to 
supply PCBs with the SMT components pre-soldered.  So in response to 
this I have put together some 'kit' options ...

http://burnit.co.uk/sdiy/index.php?page=4xd&subpage=kits

I'm really not very keen on taking on lots of repetitive soldering work 
- soldering 1 PCB for personal use is a pleasure, but soldering the same 
PCB over and over is just no fun - so I've also put together a tutorial 
on surface mount soldering for those who have no experience in this area:

http://burnit.co.uk/sdiy/index.php?page=4xd&subpage=soldering

I'd like to order the PCBs on 17th July, so please get back to me with 
pre-orders by then.

Seb

P.S. I've added a new feature to the software to do list: 'resampling' 
mode.  This gives a new behaviour when the delay time is changed in real 
time.

The default behaviour is 'crossfading' mode where the old delay buffer 
position is crossfaded over a few ms with the new delay buffer position 
to avoid clicks and glitches.

The new 'resampling' mode will alter the pitch of what is current in the 
delay buffer, giving a similar effect to a BBD based delay where the 
sample rate is varied to change the delay time.  I've sussed the require 
DSP algorithm: basically the existing buffer contents will be treated as 
a time series, and the required points will be interpolated to get the 
buffer read at the speed necessary to 'catch up' to where the buffer 
pointer should be (this works even if the delay time is continuously 
varied).  The big difference between this and a BBD delay (apart from 
the noise floor of course, and the fact that the delay time goes up to 
670ms) is that once the delay time stops being changed, and the buffer 
pointer catches up to where it should be, then the delay quality is 
again perfect 48kHz (as opposed to a BBD with long delay times where the 
sampling rate ends up at some murky depths).



-------- Original Message --------
Subject: 	4xD Quad Flanging Delay
Date: 	Wed, 21 Jun 2006 22:29:11 +0100
From: 	Seb Francis <seb at burnit.co.uk>
To: 	Synth DIY <synth-diy at dropmix.xs4all.nl>



Hi,

I'd like to announce my latest project: the 4xD Quad Flanging Delay.  
It's kind of taking the Box-O-Trix modular effects processor concept and 
applying it to a digital delay/flanger.  In fact, it could be 
inter-patched quite nicely with the Box-O-Trix if you like a bit of 
compression or distortion in your feedback loop!

http://burnit.co.uk/sdiy/index.php?page=4xd

It might also be of interest if you want to have a play with audio-DSP 
programming (read near the bottom of the page).  The design has been 
somewhat improved since my previous post - it's now using dsPICs with 
many more pins so they can access the SRAM without wasting instruction 
cycles moving the bits around to suit the available I/O.  And while I 
had all those pins free I decided to go for bigger SRAM.

Anyway, as with the Box-O-Trix, I'm hoping some people would like to 
share the cost of the PCB run with me.  As before I'm not sure of the 
price until I get an idea of numbers, but I'm hoping it'll end up at £30 
or less per PCB.

One thing to bear in mind is this uses quite a lot of surface mount 
components.  I've tried to keep them all as big as possible (i.e. 0.8mm 
pitch), but the CODEC ICs are only available in a 0.65mm pitch TSSOP 
package - having said this though, I didn't have any problems soldering 
one onto a surface mount adapter just using a flux pen and my normal 
soldering iron.  There is the possibility I can sell a *small* number of 
these PCBs with the surface mount stuff pre-assembled - but I don't want 
to become a factory worker, so I would prefer not to.

It's fairly early stages at the moment - I'm still designing the PCB 
layout - but I'd like to get an idea of the amount of interest, so drop 
me an email if this tickles your fancy :)

Seb