DSP ...(Re: RE: Digital Echoplex and TC Dual Delay...)

[PERILLE <perille@club-internet.fr>]

Kim wrote :

> the reason for this is not the price of memory, but the price of
> processors. DSP processors usually have small address spaces, so they can
> only access small amounts of memory. The DSP procs that have large 
>address
> spaces are very expensive, and not likely to be used in low/mid range 
>audio
> products. The cheap DSP procs have much smaller memory area (usually
> requiring expensinve sram memory chips), which is why you see them with
> small loop times. This is why signal processing boxes are usually not 
>well
> suited for looping. Looping isn't a DSP function, it needs big address
> area, good address calculation, and good real time operation. It doesn't
> need dsp.

For instance, DJRND2 is totally based upon one single ADSP2105 directly
addressing 14 stereo loops simultaneously from one EDO/FPM 16Mbyte RAM
module. How is it possible ? => Claimed in my PCT


> When a looper function is put into a dsp box, it usually has a
> small loop time and practically no user interactivity, since the
> architecture of these boxes is not designed for much user interaction.

Sure ?

> The box is just supposed to sit there running its dsp algorithm on an 
>audio
> stream, not bounce all around it's memory responding to user inputs. So
> when you see dsp device touting looping ability, don't get your hopes up
> too high because it probably won't be that great.

Sure ?

> 
> Loopers usually are based on low-cost microprocessors, which typically 
>have
> large address spaces even on the cheap processors. The latest low-end 
>procs
> have built in SDRAM memory controllers and can access 512MB or more with 
>no
> additional parts. But these procs are not terribly well suited for DSP,
> which is why most loopers don't have fancy signal processing along with 
>it.
> These devices are great for having large memory space and being able to
> bounce all around the address area at the whim of the user. They can have
> very responsive types of interfaces, where the user can execute all sorts
> of commands and functions and the looper responds immediately. They are
> also built for having lots of control input/output, for buttons, knobs,
> displays, etc. As the cheap procs continue to get faster and more 
>powerful,
> you'll probably start seeing some more interesting dsp functions in them,
> but not on a par with something based on a powerful dsp chip. The best
> approach is to marry a dsp and a microprocessor together, but that drives
> the cost up.....

Sure ?

> 
> kim
> 

Emmanuel