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Old 20 October 2016, 14:53   #124
pandy71
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Join Date: Jun 2010
Location: PL
Posts: 1,534
Quote:
Originally Posted by jarp View Post
All this fighting and nobody RMAA'd their Amigas? Well here you go, just for pure fun, RMAA test results played from Amiga 600 rev 1 with Furia 020 accelerator, recorded by PC and Asus Xonar STX. I used multiscan screenmode and play16 to play RMAA test signal.

But there seems to be measurement errors also - RMAA says that dynamic range is 55 dB for 8-bit output but it's impossible since 8 bits allows only 48 dB, no? Theoretical limit for 14-bit would be 84 dB and RMAA says 70 dB so that is possible.

Well in any case this was just for fun. Even though RMAA measurements are poor I was hugely impressed by the quality of sound when I played back some acapella music. I was fully able to enjoy it. I mean damn, that sound chip was designed for 1985 computer and it STILL can do results which are good enough for average home audio equipment.
Thank you for this - hope it is clear why i ask for this.
Not sure if play16 do things correctly some numbers are worse than expected.
I converted RMAA signal to more proper Amiga sample rates.
They can be downloaded from http://wikisend.com/download/311120/8364_Test_RMAA.7z
There are two sample rates (period=124 and period 74), 8 bit files are 8svx and there are two types of them - plain without dither and noiseshaping and second with dither (HP TPDF) and for period=74 also noiseshaping (improved-e-weighted SoX http://sox.sourceforge.net/SoX/NoiseShaping ).
Sadly SoX has implemented limited noiseshaping (very narrow selection of sample rates as such for lower frequency noiseshaping is disabled - ffmpeg somehow support wider range of sample rate combinations).
I think that some bad results may be related to distortions related to incorrect (lack of) samplerate conversion.
Dynamics better than expected may be related to limited oversampling and maybe some errors in measurement procedure (due bad or not existing) sample rate conversion.
I will try to repeat this measurement with APx555 .

And at the end - i share same impression that Amiga audio is not bad at all if we remember that it is 8 bit, designed in half of 80's previous century and there is a lot of thing that can be improved (on software but also on HW/analog signal path side) - even slightly worse than expected numbers definitely not nullify joy and fun from Amiga music.

Quote:
Originally Posted by roondar View Post
@audio discussion:
Is it really that relevant wether or not an Amiga can compete with modern PC audio hardware which is 25 years newer and leans heavily on technologies which where either not available at all or not available for any reasonable cost back in 1985?

Of course we have better audio these days. And no, that is not at all relevant when looking at the Amiga audio out quality. It'd be much more interesting to know how it compares to audio produced back in the day by PC's and such and much less in current day high end studio performance.

The Amiga is not a high end audio device. Then again, neither was a PC back in the 90's (I'm pretty sure Soundblasters where actually quite a bit worse in the actually produced signal to noise ratio department until the AWE32*), so again why is this relevant at all?
*) as opposed to the stats on the box, which never held to any serious scrutiny.



If we're going to compare DAC performance, it should be done fairly - compare it to other DAC's from the 1980's, available for similar prices as Paula (i.e. a few dollars max). Comparing the Amiga against high end audio stuff is hardly fair (and outright silly when doing so against stuff from 2016!) and doing so does make it seem like the goal is to make the Amiga look bad (IMHO anyway).
Can't left this without explanation as it is quite clear that some of us see my question as inappropriate and assume in advance that i hate Amiga and my goal is to prove that Amiga audio is total crap.
At first there is no known official specification for Amiga audio seen as a music\sound\audio source - fair - ok - it was not the main purpose of Amiga.
At second there is not known official Paula specification covering DAC's aspects i.e. there is not known electrical specification of chip (weird as Commodore for sure defined some values and at least from time to time verified them).
I was curious about real audio signal parameters as it allow to describe system capabilities (i.e. approach to improve overall audio Amiga capabilities) side to this it may trig new directions for for example software development.
That's all - for sure it was not to compare DVD Audio where 24 bit, 192kHz audio is reference - however i proposed to use well known high quality source (as for example CD\DVD\Media player etc.) with defined sources to calibrate simple measurement equipment like PC audio Line Input so Amiga can be objectively measured and in objective way also all potential improvement can be verified - exactly same as jarp made http://eab.abime.net/showpost.php?p=...&postcount=123 .
Simple enough, nobody died, some values are not as good as expected so this need to be analyzed if this is real Amiga (Paula + rest of signal circuit) limitation or this incompatibility between signals and Amiga HW uniqueness (PC is fixed sample rate, Amiga is variable sample rate).

Side to this i'm not surprised about silence after jarp message - subjectively we love Amiga even if love is blind.

Last edited by pandy71; 20 October 2016 at 18:01.
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