Re: RE: Digital Echoplex and TC Dual Delay... MIDI!!!!!

[Kim Flint <kflint@annihilist.com>]

>>>Ok Travis and others concerned about MIDI on the new TC D-TWO... On
>>>the technical specifications at their site... at the bottom of the
>>>page under Control Interface is the good MIDI news...
>>
>>not much of a technical specification.  and the bad news is that
>>it only does "up to" 10 seconds.  what is it with people anyway??
>>
>>10 seconds, and it's a dual delay... so 5 seconds each?  limp, limp.
>>
>>I can't understand these folks.  44.1KHz * 2 bytes = 88.2K/second of
>>delay time.  $10 in commodity chips will get you 4MB, that's 45 seconds
>>of delay!
>>
>>I'd certainly pay an extra $50 for the same box with an extra 45 seconds
>>of delay.  I think most people would do that.  Quite a lot of people
>>(including me!) would pay an extra $100 for an extra minute or so...
>>
>>      /t
>
>I was amazed, too. But remember its not a loop box. They resist...
>

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. 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. 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.

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.....

kim

______________________________________________________________________
Kim Flint                   | Looper's Delight
kflint@annihilist.com       | http://www.annihilist.com/loop/loop.html
http://www.annihilist.com/  |