I installed Centos 5.3 with the CCRMA Repo, a realtime kernel, ardour and qjackctl (jack). My sound interface is a M-Audio Audiophile 2496. It all works very well on an 1,3 Ghz Athlon with 768 MB RAM recording two tracks with 16 Bit.
An article recommended recording with 24 rather than 16 bit word length to get more headroom.
Should I turn on 24 Bit recording instead of 16 Bit?
Do I have to configure Jack or Ardour or both?
24 bit over 16 bit does have quite a quality difference! I had to compile my own custom kernel to enable 24 bit mode on my M-Audio Fast Track Pro and inmediately did see (or hear) the difference. Even when you sample it down to CD quality (which is 16 bit) some of that quality does remain than when doing it 16 to 16, especially on the high range sounds.
But like peder says, if you’re just doing some demo or for basic composition and ideas 16 bit will be good for you, but for sure if you are going production quality go for 24 bit.
And assuming the question is Should I turn on 24 Bit recording instead of 16 Bit in the Ardour option menu? the answer is mostly yes.
Unless you’re just making a quick’n’dirty demo and/or are short on disc space always use as high bit and sample rate as possible.
JACK will ask for the best resolution that your audio interface can provide. It will tell you during startup what format it settles on. For example:
ALSA: final selected sample format for capture: 32bit integer little-endian
Notice that the number of actual bits of real information will vary. No device provides 32 bits, but those that get close to 24 pack the 24 bits into either 3 or 4 bytes (24 or 32 bits). So in the example above, the device is operating at 24 bit resolution, with the 24 bits of each sample packed into 32 bits before being transferred to the CPU.
JACK will only pick 16 bits explicitly if you use the -S option to the ALSA backend.