[ardour-users] Visual waves?

vanDongen/Gilcher gml at xs4all.nl
Sat Jun 4 03:17:45 PDT 2005

On Friday 03 June 2005 17:32, Zach Trexler wrote:
> On Friday 03 June 2005 11:14 am, Joe Hartley wrote:

> > It sounds like your levels are too low.  Try to get a recording level
> > up around 0dB, and it'll be much better.
> I was thinking this might be it.  Is there a good how-to on the web on how
> to accomplish this?  I really don't know how to adjust the levels, and when
> I try and mess around with it, it only gets worse.

Lets look at the complete signal path.
Some kind of transducer picks up physical vibrations and translates them to 
analog electrical signals.
This could be mic, or guitar pickup.
Or some electronic devices like a synth generates electrical signals.
All of these have different impedances and other electrical properties.
(just as a CD player has a different level of signal as a turntable, which is 
why your stereo amp has a different input for the record-player.)
In an ideal world these outputs will match the inputs you plug them in to.
Pluging a microphone into a line input will not work well f.i. An electric 
guitar into a line input is worse. A synth into a line input will work. 

So this needs to be set up correctly first.
Your soundcard may have some controls that can switch the type of input 
between line,mic and possibly phono.
All of these controls that are available in alsa are accesible in 
the /etc/asound.state file. 
You can adjust that file and then do "alsactl restore" to set the card to the 
settings in the /etc/asound.state.
You probably only have to do this once, since you probably have startup script 
that automatically loads these settings at boot.

Then the soundcard has a "mixer interface" where you can control the levels of 
the input. For a consumer card, this is a confusing mess of controls, not all 
of them may work. Several programs can access this interface, alsamixer is 
the ncurses/terminal one that comes with alsa. But mixers that come with a 
desktop environment like gnome or kde do the same thing.
For a more professional card, there are seperate apps, like envy24control.

So you set up the level on the soundcard mixer to match the level coming in.
In a studio there is a preamp or mixer with a seperate "gain" control. What 
you do then is to adjust the gain so that the loudest signal you want to 
record is 0dB (minus overhead because clipping is _bad_ when you go to 
digital. ) and you set all the next stages to 0dB, meaning that they don't 
reduce or increase the signal. And try not to touch the faders.

This then gets to the analogue-to-digital converters and then to jack and then 
to ardour.

With ardour you can monitor the signal coming in before engaging the transport 
and you can adjust all the different levels at the different stages to get as 
close as you can to the ideal situation:
As much signal as you can get without clipping. And try to get as loud as 
possible as early in the analogue pathway as you can. (but not to loud, cheap 
hardware (behringer mixer f.i.) show an amazing increase in the amount of 
noise if you boost the signal past 0dB on the master faders. I imagine the 
controls of cheap soundcards or worse.

hope this helps



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