Proper mixer settings for music playback, or hardware fixes?
joerg at openmoko.org
Sun Jul 20 20:38:59 CEST 2008
Am So 20. Juli 2008 schrieb Timo Jyrinki:
> 2008/7/18 Hans L <thehans at gmail.com>:
> > Just a guess here since I haven't even had a chance to look at these
> > settings yet, but maybe the second frequency(after the @ symbol)
> > represents the sample rate? So depending on the sample rate you are
> > playing, you can set a different bass frequency cutoff?
> 2008/7/18 Joerg Reisenweber <joerg at openmoko.org> wrote:
> > Please refer to Wolfson WM8753 datasheet - link to be found on wiki
> I checked the datasheet. Indeed it means sample rate, but one that
> scales. There's a table specifying eg. that if you select 100Hz
> cut-off @ 16kHz, it means that at 48kHz the cut-off is 300Hz. I guess
> the names in alsamixer have been chosen according to even numbers, so
> that they actually really scale from lowest setting to highest.
> It's just that the scale seems to be opposite to reality, ie. the
> highest cut-off frequency actually results in the lowest. Most
> probably the setting I chose (200Hz @ 8kHz -> 1200Hz @ 48kHz) actually
> represents 130Hz @ 48kHz, and the one named as such (130Hz @ 48kHz) is
> in reality that 1200Hz @ 48kHz since it sounds so thinny.
> Problem solved, the cut-off is 130Hz which is quite high for
> headphones but ok for portable speakers.
nah, this is +-3dB point - not exactly cutoff.
so if you select 130Hz @ 48kHz and try to boost bass frequencies you get poor
results, as there is only a boost of frequency below 130Hz.
It's not reversed, it's just not cutoff frequency if you chose positive value
for bass level.
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