Amiga Sound Quality

[Amiga1992]

Originally Posted by Mrs Beanbag

Indeed but you can't play them other than resampled at 44.1kHz

I'm not really sure how it works, you know that I am no coder
I would love for the dev of Chipsounds to come have a go at his view on this matter.

[pandy71]

Originally Posted by Mrs Beanbag

We're splitting hairs here, it's only a word game to argue about whether it's a "sample" or not if the data has been procedurally generated rather than recorded. Anyway what if it was synthesised on another computer and sampled onto the Amiga? I can see no point in this line of argument.

You can form complex sound by Amiga HW without CPU load (almost) complex as complex can be AM/FM modulation of sample by sample...

Originally Posted by Mrs Beanbag

The Amiga's sound generation is purely digital up until the DAC. It is not possible to generate any analogue wave. That's all that matters. Of course, square waves are easy.

Same as for example on 6581 which is not analog but digital sync build around NCO concept. 6581 have only digitally controlled analog filter but you can add this to Amiga too.

Originally Posted by Mrs Beanbag

But I gather some emulators and mod players "interpolate" the samples, reducing aliasing and giving what is in theory a higher-quality sound, but losing something in the translation.

In addition, Paula doesn't run at the 44.1kHz that a modern sound card resamples everything to, so there is bound to be a difference. Perhaps this is noticeable?

So most of the soundcards use 48ksps instead 44.1ksps - and Paula can run with such speed but it need to be externally clocked (28.224MHz) and in fast mode (ie H sync faster than in normal TV mode) - AUDxPER $50.

Oer perhaps you are lucky one and your Amiga will work with SysCLK 43.7472MHz

And resampling is not as bad as audiophile people says...

I forgot to add that You can keep perfect shape of original signal only you need to use https://en.wikipedia.org/wiki/Window...angular_window in your resampler.

[john1979]

Originally Posted by pandy71

And resampling is not as bad as audiophile people says...

That depends on the algorithm. Creative have thankfully got their act together on this front now but in the past it wasn't transparent at all.

Resampling these days with modern tools (like SSRC) is quite safe though.

[pandy71]

Originally Posted by john1979

That depends on the algorithm. Creative have thankfully got their act together on this front now but in the past it wasn't transparent at all.

Resampling these days with modern tools (like SSRC) is quite safe though.

Yes, also we learn many things from Amiga (half of 80's) about digital audio - probably Paula designer never hear about dither, noise shaping etc in this times - even small trick like panning (so each channel can be placed arbitrary between Left and Right) and linked or combined mode where channel DMA slots can be allocated to form twice faster one channel can be very useful today...

[Thorham]

Originally Posted by Mrs Beanbag

In addition, Paula doesn't run at the 44.1kHz

It can actually run much higher than that using the CPU. You mean that the audio DMA normally doesn't do 44.1 khz. On systems that allow double scan screen modes (AGA) the speed of the audio DMA can be doubled to around 56 khz.

[Mrs Beanbag]

Originally Posted by Thorham

It can actually run much higher than that using the CPU. You mean that the audio DMA normally doesn't do 44.1 khz. On systems that allow double scan screen modes (AGA) the speed of the audio DMA can be doubled to around 56 khz.

No I mean that Paula decrements its internal counter at 3,579,546 Hz.

[Thorham]

Originally Posted by Mrs Beanbag

No I mean that Paula decrements its internal counter at 3,579,546 Hz.

Okay, sorry about that Pretty insane rate, though, 3.5 mhz

[Mrs Beanbag]

Originally Posted by pandy71

You can form complex sound by Amiga HW without CPU load (almost) complex as complex can be AM/FM modulation of sample by sample...

Yes you can modulate, but not by an analogue waveform, only by tables of period/volume data. There are no built in waveforms.

Same as for example on 6581 which is not analog but digital sync build around NCO concept. 6581 have only digitally controlled analog filter but you can add this to Amiga too.

6581 has built-in wave forms. Amiga does not have any built-in wave forms. Amiga cannot produce ANY SOUND unless some non-zero data is present in chip RAM.

[pandy71]

Originally Posted by Mrs Beanbag

No I mean that Paula decrements its internal counter at 3,579,546 Hz.

Nope, Paula decrement SysCLK/8 and SysCLK can be provided different than original i.e. different than 28.37516 MHz for "PAL" or than 28.63636MHz for "NTSC".

Originally Posted by Mrs Beanbag

Yes you can modulate, but not by an analogue waveform, only by tables of period/volume data. There are no built in waveforms.


6581 has built-in wave forms. Amiga does not have any built-in wave forms. Amiga cannot produce ANY SOUND unless some non-zero data is present in chip RAM.

I think you are confused by analogue, waveform and built-in - 6581 is hardcoded HW design where HW in Amiga is "less" hardcoded.
6581 is digital chip (NCO, hard coded wavetable) with analog filter and digital ring modulator.

More about 6581 internals http://sid.kubarth.com/articles/inte...ob_yannes.html

[daxb]

Every pc soundcard resample to 44,1kHz (or higher but fixed)? I only know that in the past (`90) they were so stupid to have only one fixed frequency. Thought todays cards support variable (e.g. 11kHz to 96kHz) frequencies.

About the topic:
For classic 8 bit sample stuff you will more or less have small differences in quality (emulation <> original). If you use tracker like DigiboosterPro/OctamedSoundStuio or Sequencer like HD-Rec with 16 bit 44,1kHz Samples on Amiga and play the same on emulation on pc you shouldn`t here differences. Ok, the most know this already.

I wouldn`t call an Amiga is something like an synthesizer. I own a roland MC-303 (groovebox) what I wouldn`t call it a synths too because its is sample based with sound manipulation.

[pandy71]

Originally Posted by daxb

Every pc soundcard resample to 44,1kHz (or higher but fixed)? I only know that in the past (`90) they were so stupid to have only one fixed frequency. Thought todays cards support variable (e.g. 11kHz to 96kHz) frequencies.all it a synths too because its is sample based with sound manipulation.

It depends but probably no -they are fixed frequency so they expect to have audio sampled with particular frequency and they support other sample rates trough some sample rate conversion (or performed by HW or by CPU - AFAIK for example Vista and higher Windows versions not use sound HW at all - all tasks are CPU based)

Originally Posted by daxb

I wouldn`t call an Amiga is something like an synthesizer.

http://en.wikipedia.org/wiki/Fairlight_CMI - i would say that Amiga is comparable to Fairlight CMI and Fairlight CMI is named "digital sampling synthesizer"

[Mrs Beanbag]

Originally Posted by pandy71

Nope, Paula decrement SysCLK/8 and SysCLK can be provided different than original i.e. different than 28.37516 MHz for "PAL" or than 28.63636MHz for "NTSC".

Well ok, I thought that was the case but I could only find the one number. Anyway I think you get the point.

If the emulator mixes the sound into a buffer, whatever frequency the buffer plays at it is resampled from 28.x MHz.

Given that, a little interpolation during the periods in which Paula ticks over its counter, would produce a slightly more accurate result. The question is, could anyone hear such a difference? Or is nearest neighbour good enough?

Originally Posted by pandy71

I think you are confused by analogue, waveform and built-in - 6581 is hardcoded HW design where HW in Amiga is "less" hardcoded.
6581 is digital chip (NCO, hard coded wavetable) with analog filter and digital ring modulator.

More about 6581 internals http://sid.kubarth.com/articles/inte...ob_yannes.html

Ok so SID produces digital wave forms but not from an internal wave table.

SID had to be entirely self-contained and there was no room at all for a wavetable on the chip.

The Sawtooth waveform was created by sending the upper 12-bits of the accumulator to the 12-bit Waveform D/A.

The Triangle waveform was created by using the MSB of the accumulator to invert the remaining upper 11 accumulator bits using EXOR gates. These 11 bits were then left-shifted (throwing away the MSB) and sent to the Waveform D/A (so the resolution of the triangle waveform was half that of the sawtooth, but the amplitude and frequency were the same)

The Pulse waveform was created by sending the upper 12-bits of the accumulator to a 12-bit digital comparator. The output of the comparator was either a one or a zero. This single output was then sent to all 12 bits of the Waveform D/A.

The Noise waveform was created using a 23-bit pseudo-random sequence generator (i.e., a shift register with specific outputs fed back to the input through combinatorial logic).The shift register was clocked by one of the intermediate bits of the accumulator to keep the frequency content of the noise waveform relatively the same as the pitched waveforms. The upper 12-bits of the shift register were sent to the Waveform D/A.

I would call this a synth.

I would not call Paula a synth because it cannot produce any output without any input wave data.

[pandy71]

Originally Posted by Mrs Beanbag

Ok so SID produces digital wave forms but not from an internal wave table.


I would call this a synth.

I would not call Paula a synth because it cannot produce any output without any input wave data.

SID is not able to produce any sound without CPU - same as Paula...

Synth mean you not limited to play but also to create (for example in algorithmic way).

[chaos]

But if you look at it like that, couldn't then every sound card be considered a synthesizer?

[Mrs Beanbag]

Originally Posted by pandy71

SID is not able to produce any sound without CPU - same as Paula...

SID able to produce sound without access to RAM (no DMA). CPU is only needed to set hardware registers (period, volume &c).

Synth mean you not limited to play but also to create (for example in algorithmic way).

Synth means acting as a source of waveforms. SID is a source of waveforms. Paula gets waveforms from RAM that CPU has initialised. CPU may run a software synth but Paula is just output device able to modulate the waveforms but not create them.

[Amiga1992]

Yeah what Beanbag is saying... Calling the Paula a synth is really, really far-fetched.
With this definition, my laptop is a synth, and so is my iPad :P

[commodorejohn]

Paula isn't a synthesizer; it's just a playback device with some wave-munging capabilities (FM & AM.) You can use it as the output device for a software synthesizer, if you like, but it's not inherently a synthesizer unless any sample playback device is a synthesizer.

[Loedown]

This has been one of the best threads I have read in a long time, excellent comments too and fro and no one has gotten heated about it. I have also been forced to do some heavy reading which I don't do enough of these days.

Synthesizer is something that can use wavetables or analog oscillators or additive synthesis etc. but a sampler would be something that can only use samples. Throughout the years I have been fascinated by the manner of how these machines worked and indeed their strange idiosyncracies, each instrument having its own unique sound.

[xArtx]

Yes, and I get to casually walk away whistling, totally innocent like...

[pandy71]

Once again - 6581 can't produce sound without CPU, Paula can't produce sound without CPU, CPU is absolute must.

Did ZX Spectrum can be considered as synthesizer? - YES!
[ Show youtube player ]

Synthesizer is defined by functionality not by particular HW implementation as even for digital synthesizers with analog modeling like for example older Roland JP-8000 or modern Roland SH-201 they require to use samples, buffers, DAC's to produce sound.
I would avoid to define functionality in freely programmable systems and Amiga have freely programmable system thanks to CPU+Paula.
Anything can be synthesizer [ Show youtube player ]

Btw there CSound for Amiga (quite old but anyway).