From: kholland@hydra.unm.edu (Kiernan Holland)
Subject: Re: C= speaks!!! let's spread the words!!!
Date: Thu, 13 Aug 92 08:33:57 GMT
Organization: University of New Mexico, Albuquerque
Distribution: comp

In article <34212@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes:
>In article <1992Aug6.214156.16169@mpifr-bonn.mpg.de> mlelstv@speckled.mpifr-bonn.mpg.de (Michael van Elst) writes:
>
>>The Amiga has 4 voices which are arrange as 2 stereo pairs. As I said,
>>a stock A500 can play 8 voices with software help.
>
>That's functionally correct, but the nomenclature is a bit off.  Typically,
>you refer to an independent D/A as a channel.  Thus, an A500 has four 
>8-bit channels with 6-bit volume control, a traditional CD player has

IT is interchangeable. If you are a synthesizer, MIDI freak like me, you can call them
voices or channels. But you must specify MIDI or Audio before anyone gets 
your drift.

>two 16-bit channels (no volume control).  This is a big difference when

Actually, the CD systems do. If you can possibly control the 65,556 
amplitude levels that 16-bit DAC's generate.

>compared to hardware synthesizers when you're playing pre-computed data,
>such as samples.  With samples, you have an unlimited number of voices

Well, you mean a variety different waveform
s mixed together, not unlimited voices. 
By your definition, I could say a organ has several thousand voices, 
or would require several thousand oscillators to synthesize the correct harmonics.
They become unlimited when you have a program that can mix 
waveforms fast enough. You can call it overdubbing since the effect is 
the same.

>(eg, independent sounds) per channel.  If, instead, you're running some
>kind of audio synthesis program on the Amiga, the number of independent
>voices available is certainly based on how many can be synthesized and
>summed into each available channel in real time. 

Correct. But you must have a really fast CPU to do it, and it doesn't always
sound like a hardware implementation, if such 8-bit 8 voice DAC's 
existed for the Amiga. It always sounds like 4 voices trying to 
sound like 8 rather than 8 voices. 

>
>More traditional synthesizer devices, such as the SoundBlaster or the SID
>chip on the C64 do this differently.  They have programmable sound 
>synthesizers, each of which determines a single voice.  No amount of
>CPU power in the world can synthesize extra voices from such units (the
>C64 and SoundBlaster apparently each have limited direct D/A as well), but
>one can help make up for this by supply enough hardware voices to compensate.
>Typically, such synthesizers are programmed to deliver a particular sound
>by the CPU (the complexity varies by the hardware, the C64's is a simple

One Soundblaster user could not belive me when i said to 
him that a sounblaster can't playback sampled sounds with the 
20 voices supplied by the soundblaster. These voices are only 
Yammaha FM chips (4-op) or limited FM synthesis.                            

Users should know the difference between Subtractive, Additive, 
FM, AM and FM/AM synthesis. 

FM is only half of the solution. You need the CPU to tweak your volume 
about 28,000 times per second for each of the 20 voices 
before you can have a 20 voice sampler. Talk about a snail-paced
486. ;-)  Amiga's have AM/FM synthesis, known as a sample playback.
The AMiga doesn't even waste time on its 4 voices. 
To get a PC user to simulate 4 voices on his Soundblaster, the 
CPU must add together 4 seperate waveforms and dump the result to 
the 8-bit 1 voice DAC. Actually, the number of voices you can simulate are 
limited by the frequency of your playback becuase those waveforms can get 
awfully crowded. The Depth of your sound is dependant on 
the resolution of your sound processor. While the Amiga has 256 levels 
of amplitude for 4 channels, each channel has its own 65 volume 
level VCA. This means that you can create music with more depth 
if you can controll both the sample's amplitude and the volume controlls.
That's why sooo many have talked about simulating more resolution with the 
Amiga. Acording to my calculations, you could simulate 14
bits of resolution (around 16 thousand amplitude levels).
Or realistically (64*256)+1 amplitude levels.. 

I can't see why anyone would want a Soundblaster Pro, unless they 
really like Synthesized sound. I would rather get a 
Roland CM-64 which has 64 voices with more than 80 pre-sampled 
.25 second waveforms, and full multi timbre capabilities.
A bloody MT-32 has 128 volume levels per voice and 128 position-panning,
32 voices, a drum-set, 128 presets, midi, and 10 levels of 
reverb built-in. You can get a refurbished one for                 
300 bucks. I bet if CBM made a deal with Roland, Roland might start
making sound boards with 32 voices and near CD-wuality sound. 
My MT-32 sounds like a bloody studio. I could even make all the 
PC users shut up by just demonstrating my little music box. 

Next I'm getting a Alesis machine (HT-48? or Maybe a Midiverb III?, 
one of those).

CBM needs to consult with Alesis. That's the ticket. ;-)
>ADSR envelope, three voices available), and this sound is continuously
>produced until changed by the CPU.  D/A, on the other hand, requires some 
>kind of active feed on a constant basis (the Amiga's D/A is driven by a 
>DMA channel, so like the synthesis chips, the CPU is only involved when a
>sound change is necessary).  If you have enough CPU power, the D/A approach
>is much more powerful -- all DSP's work this way.  If you have limited CPU
>resources, the synthesizer chip approach (used in virtually all 8-bit
>system with any kind of decent sound) is more powerful.  
>-- 
>Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
>   {uunet|pyramid|rutgers}!cbmvax!daveh      BIX: hazy
>	"Work like a horse, drink like a fish"	- Psychefunkapus
>