Oric's 8912 volume scale
Posted: Mon Jul 18, 2016 7:02 pm
Hi, i'm new here.
The question is related to audio output volumes.
Normally they are logarithmic so that +2 volume equals *2 amplitude.
Normally channels are mixed linearly so two channels playing the same sound equals twice the amplitude.
All similar chips (AY 8910, YM 2149) should behave the same.
Well... Not quite right.
It's known that on the Atari ST the audio mixing isn't linear. Emulators use a 4096 entry table, which was obtained by measuring the output levels.
I myself experienced wrong output when playing an oric music on the atari.
But...
When applying the normal rules to my old oric music rips (in my soundchip emulation) i get wrong results again.
It seems ok up to volume 13 but then it starts to become too loud.
So i'm wondering if the sound doesn't saturate, say, 3 channels together are 3V and this is perhaps too much for the small loudspeaker or the electronic itself.
However even a single channel with volume 15 is too loud.
I know my oric sound memories are a little rusty, but nevertheless.
My question is : do someone know what exact rules to apply when mixing sound channels so it'll sound exactly like the oric ?
The question is related to audio output volumes.
Normally they are logarithmic so that +2 volume equals *2 amplitude.
Normally channels are mixed linearly so two channels playing the same sound equals twice the amplitude.
All similar chips (AY 8910, YM 2149) should behave the same.
Well... Not quite right.
It's known that on the Atari ST the audio mixing isn't linear. Emulators use a 4096 entry table, which was obtained by measuring the output levels.
I myself experienced wrong output when playing an oric music on the atari.
But...
When applying the normal rules to my old oric music rips (in my soundchip emulation) i get wrong results again.
It seems ok up to volume 13 but then it starts to become too loud.
So i'm wondering if the sound doesn't saturate, say, 3 channels together are 3V and this is perhaps too much for the small loudspeaker or the electronic itself.
However even a single channel with volume 15 is too loud.
I know my oric sound memories are a little rusty, but nevertheless.
My question is : do someone know what exact rules to apply when mixing sound channels so it'll sound exactly like the oric ?