Re: [gentoo-user] Advice Needed: Conexant HD-Audio noisy audio

[Michael Mol]

On Tue, May 15, 2012 at 2:55 PM, Ignas Anikevicius
<anikevicius@×××××.com> wrote:
> On 15/05/12 17:52, Michael Mol wrote:
>> I have a strong expectation that part of what you're hearing is system
>> electrical noise.
>>
>> What happens when you set:
>>
>> * Master -> 100
>> * Headphone -> 100
>> * Everything else -> 0
>
> If I do not play anything while PCM is at 0 and Master and Headphone are
> at 100, then I do not hear anything. But if I start 'playing' something
> while still with PCM at 0 (no sound can be heard), then I start hearing
> irregular clipping sound.
>
> Is that what you expected?
>
> If I decrease the sound to a level where I stop hearing clipping, then I
> can barely hear the music. Although the same headphones play on my
> player fine.
>
> And It's a shame, that I indeed hear clipping. Are there any ways to
> increase the sound volume without increasing the mixer setting in ALSA?

There are going to be multiple sliders which affect your playback
volume. Without seeing a list of your sliders, I couldn't really guess
which, beyond 'Master', 'PCM' and 'Headphone'. There may be others; my
old Sound Blaster Live had a ton of internal signal processing
sliders, and anything that involves amplification presents that risk.

Each one of those will likely have a threshold where you'll risk
clipping if you go above it. I.e. if PCM and Headphone are at 50, but
Master is above $master_threshold, you may hear clipping. Likewise, if
Master and Headphone are at 50, but PCM is above $pcm_threshold, you
may hear clipping. Similarly, 'Headphone'...

There is probably a combination of settings which works best, and
sounds fine. The trouble, of course, is finding the maximum safe
threshold for each.

Me, I'm fortunate; my Intel-HDA-compatible cards all tend to say
things like "-5dB" or "+20dB" when I'm using the console Alsamixer,
and I've established that as long as they say "0dB", I get the best
signal I can get.

> Would a different sound card help?

Sure; you could use a card with more post-mixer amplification. Or a
card with little to no mixing options. Or an external amplifier.

> Is there any way I can solve the
> problem without buying new hardware?

You might try using something like PulseAudio, which may be doing
internal mixing in the floating point space before it maps back to
16-bit linear PCM. My experiences with PulseAudio have generally been
positive in terms of audio quality. The trickiest part is getting
applications to pipe their audio through it, followed by getting
direct access to the card's mixer settings if I need it. But
"pavucontrol" as a mixer control for PulseAudio works reasonably well
for the majority of circumstances.

>
> Thanks a lot for help,

np.

(Note: I CC'd this back to the main list, because somehow this one got
sent to me directly. Channeling communications through the main list
keeps the archives useful.)

-- 
:wq