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General Category => Technical Support - General => Topic started by: mr_lou on 09:44, 10 April 24

Title: Amstrad CPC volume decibel table?
Post by: mr_lou on 09:44, 10 April 24
Here is a nice table showing Amiga volume decibels.
http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node00F1.html

Does anyone know where I can find a similar table for the Amstrad CPC volumes?
Title: Re: Amstrad CPC volume decibel table?
Post by: McArti0 on 10:54, 10 April 24
AY3-8912 has manual and amplitude curve. Resistors mixer at mono line is another then resistors mixer at stereo lines.
Title: Re: Amstrad CPC volume decibel table?
Post by: mr_lou on 12:36, 10 April 24
This is useful. I've made my table conversion using this:
https://map.grauw.nl/articles/psg_sample.php#8bitsamples
Title: Re: Amstrad CPC volume decibel table?
Post by: Targhan on 13:16, 10 April 24
These are the 16-bit values I use for Arkos Tracker. They are more accurate than the datasheet you can find, as they were tested electronically by Grim and Zik.

0, 231, 695, 1158, 2084, 2779, 4168, 6716,
8105, 13200, 18294, 24315, 32189, 40757, 52799, 65535
Title: Re: Amstrad CPC volume decibel table?
Post by: McArti0 on 17:04, 10 April 24
Hmm ay3 manual show different values.

2 steps down = half values down.

1, 0.707 , 0.5 , 0.303 , 0.25 , 0.1515 , 0.125 ......

Title: Re: Amstrad CPC volume decibel table?
Post by: Targhan on 22:30, 10 April 24
They're probably wrong :). Grim and Zik recorded the values directly from the CPC.
Title: Re: Amstrad CPC volume decibel table?
Post by: McArti0 on 07:05, 11 April 24
But from sound or one stereo channel?
Title: Re: Amstrad CPC volume decibel table?
Post by: eto on 09:19, 11 April 24
Quote from: Targhan on 13:16, 10 April 24These are the 16-bit values I use for Arkos Tracker. They are more accurate than the datasheet you can find, as they were tested electronically by Grim and Zik.

0, 231, 695, 1158, 2084, 2779, 4168, 6716,
8105, 13200, 18294, 24315, 32189, 40757, 52799, 65535

That's quite a difference to the expected values. At which point did they test those values? IC output pin of each channel? Or after the sound is mixed? 

I once started testing the output levels (to be fair, with a multimeter only) and it was very close to the theoretical value based on the data sheet and how the CPC mixes the channels. 

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