The Logic Off Topic list

GA Moore wrote:

>I suspect that the digital recreations of the analog circuits are more
>precise and accurate and less noisy.
Does 'suspect' mean you're not sure?

>However for greater variety, that
>can eventually be programmed into the software too. If you can identify
>exactly what the affect you want, it can be programmed.
Can't argue with an 'if'.

>The word 'model' can be used two different ways.
??
The only two ways you can use this word that I can see, in this present 
context anyway, would be what we could perhaps call 'first-order' and 
'second-order' modelling. In first'order modelling you would possibly model 
the actual behaviour of a real something. In second-order modelling you 
would perhaps model the behaviour (or method) by which some other 
first-order gadget models something else?

But even then ... as far as I can see ... that could eventually be reduced 
to a simple case of first-order modelling because what you would actually 
be modelling is the behaviour of a very real something ... whose behaviour 
just happened to include the ability of that something to model something 
else. You do not actually have to know that you are modelling something 
that can model something else when you are trying to model that something. 
What are your two different ways of modelling something. I'm genuinely 
curious ... for as far as I can see the objects under discussion are all 
trying to model something and so I'm a little puzzled what the difference is.

>In a theoretical sense,
>we have digital models of the analog, but things like the Microphone
>Modeller and the POD use modeling in a different sense - which is more
>like samplying what happens when various signals are fed in and looking
>what happens. They even take into account how adjusting the controls
>interact with each other on various models of amps.
I do not understand how either the Antares Microphone Modeller or the POD 
are modelling 'in a different sense'.

Also ... does the modus operandi of Microphone Modeller truly have 
something to do with sampling? I thought the mathematical basis of all 
filtering, which as far as I know is basically what the MM does, was 
convolution? Or am I mistaken here? I thought, but I could be wrong, that 
the output of any digital filter, say a function y(k), was related to its 
input, say a different function x(k), through the relevant impulse 
response, another function, h(k)? Not that this is my area of expertise, or 
anything of course. I am happy to bow down to superior wisdom ... but I 
always thought that what related the two was convolution? So ... what this 
boils down to is how we come by the various functions, no? Well, that's a 
whole other issue in itself, but as far as I can see an input response 
FUNCTION is not a sample. One can criticize the MM for making some pretty 
unrealistic assumptions about the nature of its input functions and for the 
arbitrariness with which it selects the impulse responses, but I don't see 
how one criticize it for not being a sample when it isn't??!  Anyway, as 
far as I know the MM has anything remotely to do with sampling but uses 
some pretty nifty Fourier techniques to achieve its purposes.

If the impulse response has a finite length, and the input also has a 
finite length then -- at least that's what I always thought -- it is only 
necessary to store x(k) in a suitable vector and then convolve the two. 
You'v got blind source separation and all kinds of other stuff. You need 
source separation algorithms as well. You do have to deal with the reverb 
and absorption characteristics of your room. But this only needs finite 
impulse responses or FIR filters. You still only need to convolve, though, 
with whatever FUNCTION you devise to represent the original sound source. 
That's what I thought, anyway. Where's the need for sampling in the 
operation of such a device? I could be wrong about this, though. It's a 
well-known fact that I'm wrong about many things. But usually I'm fortunate 
in that when I do parade my ignorance -- way too often I admit -- some kind 
soul somewhere graciously corrects me and my knowledge increases.

Kool Musick
Keep Musick Kool


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