SuperPAULA - if you have experinece in amiga music please give feedback

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Karlos wrote:

bloodline wrote:

That's rather clever and almost certain to take a million years...

It's seemingly just a lookup table. I wasn't going to do it by manual inspection. I was going to graph the differences ;-)

Well get on and do it... if not let me know, and I'll build a look up table based on my idea...

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ChrisH wrote:

Can anyone here publish the original Paula response curve? I'd love to write a paula effect processor!

Actually... I probably have all the equipment needed to find it out myself... does anyone know a decent menthod?

I would imagine the best way to *generate* the Paula response curve would first require you to know what kind of D/A converter Paula used.  I *vaguely* recall it used a series of (9?) resistors to get the voltage drops required for each of the 8 bits, which is not very accurate due to the resistor tolerances, and therefore tends to produce a non-linear response curve.

An R-2R Ladder DAC eh? I guess that would work for something as simple as 8 bits... Ok... are these integrated on the Paula IC or on the Board? I need to find a Paula pinout..

Assuming my recollection is correct, then you need some method to find the relative values of each of those (9?) resistors.  That should be MUCH more accurate & less error prone, especially compared to trying to sample the output of Paula across her entire dynamic range.

It would be easy to work out... but that's not going to give me real word performance.

I imagine that the 14-bit audio calibration tool used some clever method to accurately find out the relative resistor values, so that it could then compensation for them.

IIRC the calibration tool was rather subjective... which required you to decide when the response was linear... it was a long time ago...

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Looking at an A500 schematic it seems the Audio DACs are actually in Paula herself... pretty cool...

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Karlos wrote:

bloodline wrote:

That's rather clever and almost certain to take a million years...

It's seemingly just a lookup table. I wasn't going to do it by manual inspection. I was going to graph the differences ;-)

The CyberSound preset calibration file is a table of 256 1byte values (I assume they are signed, since Paula is...)... I wrote a quick program to examine it... I'm not sure exactly how these numbers are used to transform the audio?

I'm going to build a few graphs until I get something meaningful...

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Ok... I think I've figured it out...

Each byte in the the calibration file seems to correspond to the difference between what one would expect  the 8bit->16bit value to be (using simple LSL scaling) and what the Amiga actually produces... This is the only way I can make sense of the file... anyone have any other ideas?