Falcon DAC volume control

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joska
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Falcon DAC volume control

Post by joska »

How do I set the DAC volume on the Falcon? When looking at the register listings I can only find the ADC volume, but I need to set the DAC output volume.
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Cyprian
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Re: Falcon DAC volume control

Post by Cyprian »

I'm not sure if it exists (four stereo channels but only one stereo DAC). But DSP can do that.
In my Falcon the DAC volume level was changed by changing some discrete elements.
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neanderthal
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Re: Falcon DAC volume control

Post by neanderthal »

Well there sort of is,tho its called attenuation,resides in $ff893a.w bits LLLL RRRR .... according to my old hardware.txt
0000 = no attenuation
1111 = -22.5 dB
in 1.5 dB steps according to datasheet.
Was years ago since played around with that but think its correct adress in falcon.
Have some local notes that maybe should put up somewhere.
joska
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Re: Falcon DAC volume control

Post by joska »

That's the attenuation for the ADC, i.e. YM and microphone input. It only affects YM/microphone volume, not DMA sound volume. I think Cyprian is right and that there is no "master volume" on the Falcon :(
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czietz
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Re: Falcon DAC volume control

Post by czietz »

According to https://docs.dev-docs.org/htm/search.ph ... 0+Develope there is a control for output (i.e., DAC) attenuation:
output.png
So, you're saying that it does not work (or is not implemented)?

EDIT: Opcode 130 refers to XBIOS, BTW.
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Cyprian
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Re: Falcon DAC volume control

Post by Cyprian »

interesting,
more details there:

http://toshyp.atari.org/en/004012.html#soundcmd
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joska
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Re: Falcon DAC volume control

Post by joska »

I stand corrected. ff893a is indeed the "master volume" on the Falcon. ff8939 is the ADC volume, i.e. the analog input (to which the YM and the microphone input is connected) amplification.

In my defense I have to say that I was fooled by two things:

1. The docs/register listings I've seen say the format of ff893a.w is "LLLLRRRR", but in reality it's xxxxLLLLRRRRxxxx. So if you only write to the upper byte you will only affect the right channel, which in my case is not really audible because my Falcon is connected to a mono speaker...
2. The SNDH replay routine used by MaxYMiser resets this register (and the ADC volume, most likely to ensure correct YM/DMA balance) when you start a song which use DMA samples on a Falcon. So any attenuation set was simply ignored as my testcase was exactly this.
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