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Old 21 January 2015, 14:19   #21
Thorham
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Quote:
Originally Posted by demolition View Post
the audio from the Amiga is not exactly high quality and already quite distorted from Paula
Calibrated 14 bit audio can sound quite good, so it's not exactly low quality either.
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Old 21 January 2015, 14:25   #22
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Calibrated 14 bit audio can sound quite good, so it's not exactly low quality either.
14 bit can sound good, but in the case of the Amiga and particularly the 1200, it is distorted since there are a lot of aliasing products in the output and the low pass filters are not aggressive enough to remove them (the 1200 has simpler filters than the previous models). And if it was, it would sound very dull since the bandwidth is not high enough.
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Old 21 January 2015, 17:38   #23
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Originally Posted by demolition View Post
14 bit can sound good, but in the case of the Amiga and particularly the 1200, it is distorted since there are a lot of aliasing products in the output and the low pass filters are not aggressive enough to remove them (the 1200 has simpler filters than the previous models). And if it was, it would sound very dull since the bandwidth is not high enough.
It doesn't sound very distorted to me. The only issue with 14 bit is the non-linearity of the DACs which produce some hissing noise at low volumes. Generally, good audio sources sound good in 28 khz (down-sampled with SOX) or 44 khz (double scan modes on A1200).

Really, people keep saying this stuff about those filters, but I would really like to hear an example of this distortion.
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Old 21 January 2015, 18:10   #24
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Once you notice it, it becomes hard to not hear it when the filter is disabled. You hear it as aharmonic high frequency tones (or noise depending on what is being played). If you play back a sine sweep (or use some tone generator), it should be very noticable.

To me, this is just how the Amiga sounds and it wouldn't sound Amiga-like to me if it was perfect.

I have not heard how double frequency playback sounds, but it should help quite a bit and probably even make the aliasing inaudible.

The SID in the C64 is really bad from an objective point of view, and not hitting the specification very well, but it turned out that it sounded very good anyway. I don't think the C64 would be as popular for sound if they have had the more accurate 8580 sound from the beginning. For the A1200, they probably also figured that removing a filter would be fine since people generally preferred to have the filter disabled anyway in the earlier models.
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Old 21 January 2015, 21:44   #25
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If you play back a sine sweep (or use some tone generator), it should be very noticable.
With double scan mode and a 44 khz sweep file, I hear something in the higher frequency areas, but it's the same with my peecee's mobo audio, and that doesn't sound bad at all.

Quote:
Originally Posted by demolition View Post
To me, this is just how the Amiga sounds and it wouldn't sound Amiga-like to me if it was perfect.
From my experience this typical Amiga sound comes from the samples that are used in MODs. Play anything CD quality in 14 bit, and this typical sound just goes away.

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Originally Posted by demolition View Post
I have not heard how double frequency playback sounds, but it should help quite a bit and probably even make the aliasing inaudible.
It's better than a good quality source that's down-sampled to 28 khz with SOX, but strangely it's not that much better. You'll probably notice the difference with high quality classical music.

Last edited by Thorham; 21 January 2015 at 21:51.
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