One-bit synth technofobies

[BJ]

Mikko Helin wrote:
> 
> I hope this is the right list, but anyway, I've been thinking this
> really hard. You know, it is really hard, to do the job of the
> sigma-delta modulator. New designs use 128-times (Crystal) and even
> 256-times (Philips Bitstream) oversampling, which is beyond the Atmel
> AVR (AT90S1200) chip's capability. PWM is another way, but I don't
> think it could be much better than PC's speaker output (though it's
> kind of cool). But the one-bit DACs use PDM (pulse density
> modulation), which is much more difficult. The "zero" level with 50%
> of one's density is made of "01010101" looking pulse stream. The most
> negative output looks like "010010010" (30% one's density) and the
> most positive output level with 70% one's density looks like like
> "101101101101", that's it.
> Now, if I only had 64 kB of EEPROM, 16-bit registers and
> multiplication operation, all would be nicely set for an inexpensive
> soft synth. There are such chips, called DSP controllers, and they are
> also inexpensive (TMS320C15 etc.) and work at 10-20 MHz rates, one
> instruction/clock cycle, in 10-20 MIPS. Somehow they just aren't so
> fascinating.

Well, i like your minimalistic approach to electronic things.

I have since many years back a TMS320c26 EVB from
TI and i allvays wondered, what a nice DCO i could do with it.
but i never get more far then drawing the shemos, loking at som code
examples
and then i get tired, hungry,angry,sad,happy,robbed,mugged,poked etc.
But i always wonder why people in the DSP buisness newer liked or
always down spoke about those DSP's!

I have another point of view to it,if you take close look at
the C20,C50 C5xx family they are quite god,ofcours they are like a 
16 bit Intel 8031 to program so to speak.!The Intels in DSP!!

They are capable to run in a MCU mode or in CPU mode.
great for stand alone apps Like DCO, whatever)
the C50 have circular buffers in HW(nice for DCO's among many things)
C20 does not, separate IO and memory space,C20 does not have a waitstate
generator
a must today, the C50 does,and the two most strong points are they are
super cheap
in a small quantitys.And there are a vast number of different types
regarding to implemented cirquits in those DSP's.

The not so god side of those DSP's seems to me that they have
some ackvard way to get programed.But not more ackvard then
it is to program a Z80 or a 8031!And there are lots of people who 
have programed those MCU's.
If you compare to a ADSP2181 for example, who needs only 
half as much code as the TMS C50 to do the same thing!

The ADSP are in most cases better then any other Texas or Motorola DSP
in that price range and in that type of DSP.
But the ADSP are wery expencive.And the TMS are dead cheap.

Actually Texas was the only DSP manufacturer speaking about
(back in 1992 i think) and actually had a promo/data manual 
with the C20 series, with a complete synth with keyboard and knobs and
stuff!

I once subscribed to the DSP mailing list but all that they where
talking
about was "Hey man, today i have done a flanger that sounds shit"
perhaps i am to crude here but i never saw any compiled code to download
and run
on a DSP so i unsubscribed :( ..I'm not a particulary clever person or a
genius in math,
i have read Hal Chamberlins bok Musical Applications for CPU and i do
get the hint of most of
the things discussed there and if you take his example doing a wave
table osc
with a 8 bit CPU 6502 or whatever ,you could get a quite god DCO out of
that.
Why is it then so dam difficult to do this with a DSP,that i dont
understand??
Anything audio done on a CPU could be done thousand times better in a
DSP
a DSP tend do well for multiplexing digi OSC's for example.
Perhaps all this DSP thing is a attitude thing?

By the way the SiD 6581 synth on a chip is a 24 bit phase accumulator
osc.

Actually Clavia had a prototype of an Additive machine like the Technos
from Canada built with i think 92 pieces of Tms320C10 it was back in the
80's.
If i can remember right!Uhu ?? Ask Clavia if interested in that thing.
I saw this machine in a magasine somewhere!!
 
> This device could also be used as a simple sample player, at a fixed
> frequency, with one voice and with an external EEPROM. Would make a
> nice drum player! One unit for BD, another for SD, third for cymbals
> and the fourth one for the tom's. As sample playing is not so hard
> work that the other channel couldn't also be employed, as there are 59
> cycles time for retrieving the next sample (two bytes) from the
> EEPROM. You need 16 bit address bus for 64 kB, with multiplexing you
> could get more memory access (even megabytes).
> Just some thoughts (hope you don't mind),

I dont mind,i would suggest you to do this on a DSP of some kind.
Besides all this nonsense BTW,TTY,NNMO BGG, CDDD etc thing.
What the hell is a digest?? Yes i dont know and i dont bother 
to go to se in the dictionary either!!A digest here isa cockie
a nice one where you can put on some butter and cheese and have a
glas of wine and take it iiiicccyyyy! 

BJ