[alsa-devel] Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII

[Raymond Yau]

2010/2/17 Lennart Poettering <mznyfn at 0pointer.de>

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> Hmm, so you basically tuned the USB card's DAC/ADC level to the HDA
> card's DAC/ADC.
>
> I now measured the "Master" slider of my aureon (USB 0ccd:0028,
> TerraTec Aureon 5.1 MkII) with the aforementioned dbmeasure tool and a
> loopback cable. The aureon has 65536 volume steps, but
> I was too lazy to measure them all. So I only measured every
> 3000th. From the max volume to the min volume:
>
> 65536 0 dB
> 62536 0.00560039 dB
> 59536 0.00694678 dB
> 56536 0.00616732 dB
> 53536 0.00645077 dB
> 50536 0.00673421 dB
> 47536 -1.49514 dB
> 44536 -1.49455 dB
> 41536 -1.49648 dB
> 38536 -2.98666 dB
> 35536 -2.98486 dB
> 32536 -2.98536 dB
> 29536 -4.48688 dB
> 26536 -6.00084 dB
> 23536 -5.99928 dB
> 20536 -9.00246 dB
> 17536 -10.5425 dB
> 14536 -16.5274 dB
> 11536 -32.9435 dB
> 8536 -43.4326 dB
> 5536 -43.5066 dB
> 2536 -43.2968 dB
> 0 -43.4431 dB
>
> If you plot this it looks as if the card actually only implements 10
> or so discrete steps, and at around 10000 just becomes a constant
> function.
>
> ALSA reports -47.87 .. -1.97 for this. So it seems the overall range
> the USB data reports is not really that far off, but the volume
> function in bteween is.
>
> The noise level of these measurements is < -58 dB.
>
> What's the next step with this measurement data? Will you take it from
> here, or shall I provide you with more data?
>
> Lennart
>

How about dbmeasure the pulse device since the volume control seem also have
65536 step ?

Can you provide the result for the pulse device ?