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Old 13 October 2016, 19:00   #53
meynaf
son of 68k
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Join Date: Nov 2007
Location: Lyon / France
Age: 44
Posts: 2,459
Quote:
Originally Posted by pandy71 View Post
Exactly however you insisted to use AY nonuniform log scale DAC as comparable to Amiga and due internal AY design those DAC can be stacked (added) when Amiga you can introduce only fixed attenuation to lower part.
My point was just about adding several channels together to get sounds that can't be made in theory.


Quote:
Originally Posted by pandy71 View Post
Definitely not checking all codes as to do this you must provide stimulus signal that use all possible code values... all calibration doing is checking two overlapping bits (IMHO).
It's clear you don't have a clue on what calibration does


Quote:
Originally Posted by pandy71 View Post
It is 150 useful for full scale but nominally rarely sample values can utilize full scale so finally it is always less... and my claim covers all possible problems in analog path.
But do we really have problems in analog path ?


Quote:
Originally Posted by pandy71 View Post
It may have non-unique output levels but it doesn't be good (as without calibration overall error can be larger) - once again you extending analogies from arithmetic in ALU to DAC which is not justified.
But you do agree that the calibrated output must lead to less than 16384 different values, and this can be verified.


Quote:
Originally Posted by pandy71 View Post
So there is no lower 8 bit but only 6 - you have 2 overlapping bits - attenuator introduce 6 bit attenuation so in analog voltage scale you shifting 8 bit low by 6 bits.
It does not introduce "6 bit attenuation", just reduces the signal by 64. $40 with a volume of 1 is NOT the same as $01 with a volume of 64.


Quote:
Originally Posted by pandy71 View Post
Glad that everyone can express his opinion about perceived Amiga noise level.
Sure, but you didn't do the experiment.


Quote:
Originally Posted by pandy71 View Post
Same as above - i respect your opinion.
It's not an opinion. It's a fact that can be checked.


Quote:
Originally Posted by pandy71 View Post
Nope - i'm trying to cover whole analog path but you insist to speak about arithmetic operations on signal.
Apparently yes, else you wouldn't talk about -36dB coming out of the paula chip.


Quote:
Originally Posted by pandy71 View Post
Well so if they are nonlinear and you correcting 2 bits how the heck suddenly 14 bit accuracy was born?
This has nothing to do with "correcting 2 bits". It's about combining two 8-bit signals to get 14 bit.


Quote:
Originally Posted by pandy71 View Post
What kind of experience - any objective source of this claim?
Why wanting external sources ? It's an experience anyone here can do.
Try playing 14 bit on any PC (uncalibrated 14 bit running on an emulator should suffice), and compare with an Amiga running software such as Play16.


Quote:
Originally Posted by pandy71 View Post
I don't know and that's why i ask and i strongly consider to measure this (but waiting for Vampire 500).
You don't know, but according to what you said, it should be less than 16384.
I can do that measurement anytime, but first you have to be clear on what to expect. If, say, it's 17000, there's something wrong somewhere, don't you think ?


Quote:
Originally Posted by pandy71 View Post
We not talking about perfection only about objectively quantified parameters that precisely describe DAC conversion capabilities.
As said, i don't care about all that DAC theoretical stuff. What matters is the final output quality, and i know for having heard it that it's certainly not just 10 bit.


Quote:
Originally Posted by pandy71 View Post
Well, you can't expect 14 bit accuracy from a component that provide 8 bit accuracy (but due volume regulation design in Amiga with perfect 8 bit DAC it may work as Amiga for volume regulation use PWM and as such it is free from requantization issues - you can have 8 bit with AUDxVOL=1).
As i already said, the component that provides the 14 bit accuracy isn't Paula.
At the end the trick is exactly the same as if we were using 8-bit video D/A and do +1 half the time - at the end we get 9 bit (if we're fast enough).


Quote:
Originally Posted by pandy71 View Post
Ok, tell me how - we have 16 bit sample, we split them on two equal 8 bit parts, upper part is feed to first DAC directly, lower 8 bit part is feed to second DAC,second DAC has enabled attenuation of 36dB (6 bits), both DAC outputs are combined in analog domain.
The top 8 bits aren't used directly. That would be too easy


Quote:
Originally Posted by pandy71 View Post
Yes, with higher accuracy - if 16 bit DAC has better performance then analogue signal will be more accurate (same rule as using for calculation extended precision and later using only most significant bits).
But in real life a PC (16 bit DAC) won't play a 8 bit sample better than an Amiga (8 bit DAC), at least not without some upsampling.
This is a fact anyone can check.


Quote:
Originally Posted by pandy71 View Post
Well, once again asking you to not use word perfection - it works as 'reductio ad absurdum' as perfection is indefinite .
Please don't involve clock as this lead us nowhere. It will only start discussion about jitter and all related time domain problems related to signal conversion.

14 bit accuracy is not meaningless and can be easily defined - simplest approach is SNR [dB]= 6.02N + 1.76 (where N is number of bits but this is very simplistic).
More accurate are accuracy (quality) descriptions like this http://www.analog.com/media/en/train...als/MT-003.pdf
Again, just theory.


Quote:
Originally Posted by pandy71 View Post
It is not pretending but curiosity and doubt which is foundation for every person having rational approach to problem.
I have very precision audio analyzer side to me https://www.ap.com/analyzers-accessories/apx555/ - all i need is Amiga with proper signals (as APx555 internal generator can't be used) - to have a proper signals i need to spend some time to prepare those signals (re-sampling to native Amiga sample rate) and need to have Amiga capable to play it (that's why i waiting for V500).
However ANY modern PC card can be used as audio analyzer as usually they parameters are way higher than Amiga audio system capabilities.
Perhaps it's better to just wait until you have the Amiga...
If you need a program able to play any wave file, ask me (if you're not locked to old 68000).


Quote:
Originally Posted by pandy71 View Post
I have this intention especially after such hot dispute.

This may help all of us in more formalized discussion in future:
http://www2.electron.frba.utn.edu.ar...easurement.pdf
I don't want a formalized discussion, you trying to bring me to your land, huh ? It doesn't work this way.

You're not exactly answering the question...

So i will ask it again, in a different way.
Let's say we load a calibration file, then build the table giving the 65536 values. How many unique value pairs do you expect to find in the table ? (this can easily be verified ; if you don't know you can at least estimate a reasonable range)
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