[sdiy] jitter, warmth, and so on

[John Mahoney]

Portions deleted, comments inline. Aside from this post, I'll try to 
stand aside and wait for more feedback.


At 06:52 PM 4/21/2006, Antti Huovilainen wrote:
>On Fri, 21 Apr 2006, John Mahoney wrote:
>
>>         1) Assemble a set of audio files containing sound samples 
>> of various oscillators.
>
>This is in principle a good idea, but it is unlikely that the 
>differences would be audible in solo oscillators (how many really 
>"fat/warm" single oscillator synths do you know?)

I was just hoping that we could start somewhere. I was just out this 
lump of clay to see if the group can mold it into shape. Any ideas on 
how we should audition oscillators?

Is it useless to listen to single, naked oscillators? I didn't say 
that people couldn't process the osc samples through analog filters and VCAs.

Perhaps we need to listen to pairs of oscs. Octaves, perhaps? With 
detuning, or not?


>24 vs 16 bits makes no difference here - the dynamic range is 
>non-existant (it's an oscillator afterall) and how many oscillators 
>have noise level below -100 dB?

Good point.


>>Hz (A in various octaves). WAV files, not MP3, right? (Oh... Should 
>>the audio frequencies be factors of 44100 so the wavelengths are 
>>whole numbers of samples? At least, programmatically generated 
>>waves can be such.)
>
>No. This would require all VCOs to be exactly stable with no jitter 
>etc. At which point they would already be equivalent and this test 
>would be pointless.
>This is also absolutely not a requirement for the digital waves. Any 
>halfway decent digital oscillator (which probably counts out CSound 
>and vast majority of modular environments) can be made alias-free at 
>any reasonably low frequency (< 4 khz).

Yes, I understand that analog waves would fail to line up on the 
sample boundaries. I just figured that it would simplify making 
digitally-generated or looped waves.


>I'd be happy to synthesize any required tones in matlab. Just tell 
>me the jitter, drift, reset time etc specs you want.

Excellent!


>Sorry to shoot down the ideas, but I see way too often incorrect 
>assumptions about digital processing.

Don't be sorry, I'm glad you're here and I appreciate the insight! As 
is often said, one of the best things about the SDIY list is the 
range of expertise of its members. I don't even pretend to be a 
digital audio expert.


>Antti - soon to be M.Sc in audio signal processing

Nice. :-)


>"No boom today. Boom tomorrow. There's always a boom tomorrow"
>   -- Lt. Cmdr. Ivanova

I've long wondered where your .sig quote comes from.
--
john