On Sun, Aug 23, 2009 at 07:27:18PM +0100, Dan Mills wrote: > Lets say your card is aligned so that 0dbFS = +18dbu (EBU standard), > then 0Vu = +4dbu = - 14dbFS, so a software VU calibrated for 0Vu = > -14dbFs should read the same as an external Vu calibrated for +4dbu = > 0Vu. If it does not then either a calibration setting is off somewhere > or one of the meters is faulty.
True. But even a definition such as 'dB FS' is ambiguous, and it's easy to make mistakes as a result of that. Consider a sine wave that is just below digital clipping. This would be called '0 dB FS', but the actual RMS level is 3 db lower. I've seen at least one context where this same signal would be called -3dB FS. Which somehow makes sense as well. AFAIK the first interpretation is the more common one. > actually fairly common with professional cards. And it avoids a lot of problems. Semi-pro cards will not have the correct levels, but some can be quite consistent between channels. For example my Terratec EWS88MT has less than +/- 0.1 dB variation between its 8 channels, both for input and output. But the actual level is just +3.5dBu for a FS sine wave. The real misery starts when (as reported in a recent post on LAU or LAD), a user finds four volume controls between his audio file and the physical output (plus of course a fifth one on his amplifier), and then of course gets confused on how to set all of them. Ciao, -- FA Io lo dico sempre: l'Italia รจ troppo stretta e lunga. _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev