On 06/19/2010 01:57 AM, Bearcat M. Şandor wrote: > On Fri, 2010-06-18 at 22:41 +0200, fons@xxxxxxxxxxxxxxx wrote: > >> The meters are probably completely useless. >> >> The chip used in your soundcard has a digital gain control >> with a range of 0...-120 dB in steps of 0.5 dB. Does that >> correspond to what alsamixer is showing ? If not you'd >> better leave the gain at 0 dB. >> > Alsamixer reports "dB gain 0.00, 0.00" to -60.00, -60.00 in .5 dB steps. > Does that correspond to -120 dB somehow (both channels == 120 dB total)? > (i'm a newb at all this) No it does not add up that way. Maybe alsamixer is showing wrong numbers?! Fons may know more. >> If that soundcard really has the dynamic range that the >> sales blurb claims it has, then its output level will be >> a lot higher than what is expected by the average non-pro >> amplifier, including 'audiophile' ones. >> >> That means that you should turn down the power amp gain >> quite a bit. > This is a low powered 10 watt max amp (class t chip) > >> The correct alignment procedure would be: >> >> 1. Play a piece of music representative of what you >> normally listen to. Check the digital level with e.g. >> jkmeter, For classic use the K20 mode and ensure you >> have a level around 0 dB. For pop use the K14 mode >> and again ensure you have around 0 dB. > I compiled and started up jkmeter, then figured out how to output to it using qjackctl. Welcome aboard. > The alsamixer volume controls make no difference at all to jkmeter, but adjusting the > volume on mplayer does. Is this the expected behavior? Yes it is. Alsamixer controls the volume in the mixer of the sound-card. JACK is all in software. Consider the following (somewhat simplified) diagram: JACKified-audio-app (eg mplayer, ardour, jkmeter) | v JACK-server | v Soundcard ## hardware-mixer controlled by alsamixer | v Amp & Speakers When you adjust the volume in mplayer, mplayer itself scales the volume. mplayer does not interact with the soundcard's hardware-mixer. (Well, you can configure mplayer to do either or both, but the default with mplayer/JACK is to use mplayer's integrated "amp".) jkmeter (or any other JACK app) gets mplayer's audio directly from JACKd without the audio-data going to the soundcard first. > I was not sure how to activate K20 or K14 given > jkmeter's interface. You need jkmeter version >= 0.4.0. Run `jkmeter -type k14` to get the K14 scale (k20 is the default) `jkmeter -h` prints usage and version information. Information on the K-system can be found in jkmeter's README and at http://www.digido.com/level-practices-part-2-includes-the-k-system.html >> 2. Set the gain of the soundcard to 0 dB, > Done >> 3. Adjust the gain of the power amp to the maximum volume >> you'd ever expect for this tyoe of music. > Done >> 4. If you want to avoid an analog gaing control use a software >> gain control (preferred), or the ALSA gain setting as your >> volume control. > You mean individual application volume controls as opposed to the sound > card mixer is preferred? > >> If the gain setting of the card has any impact on the magnitude >> or phase response then simply the card is out of spec. >> If the gain control of the power amp has any impact on the same, >> again it's probably out of spec. >> >> As long as you don't overload anything, there should be no difference. >> Things like 'fuller bass' are impossible to comment on. If in doubt, >> *measure* it. > So even though turning down the apps volume control theoretically > reduces the resolution of the sound it should have no bearing on the > quality of the sound presented? Reducing resolution always reduces the quality - some music just needs to be played loud! :) As long as you stay in the digital domain, gain changes will not effect frequency or phase of the sound. But unless you have pro & high-quality equipment: the analog part (soundcard, amp, speakers) does in practice respond differently at different gain levels. Niles Mayer recently elaborated on that: http://lists.linuxaudio.org/pipermail/linux-audio-user/2010-June/070249.html > Or do software controls not do that at all? As long as you stay in the digital domain (here: software) it'll be "perfect". Cheers! robin > Thanks for the help Fons. I appreciate it and your fine software as > always. > _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user