[linux-audio-user] Recording from SPDIF with Audiophile

davidrclark at earthlink.net davidrclark at earthlink.net
Thu Jan 1 18:07:49 EST 2004

Regarding low levels with some 24/96 cards: The inputs are lowered to 8.3% 
to account for 12 (or so) channels so that clipping won't occur, I presume.
So if you have a 2-channel 24/96 card, your inputs are way too low
when using ICE1712, for example.  (This is true for arecord, not qarecord.)
If you do arecord with verbose output (-v), you will see exactly what the
reduction is.  I should mention that this is with analog --- I would expect
the same with SPDIF.

Transformation table:
0 <- 0*0.0833333 + 1*0.0833333 + 2*0.0833333 + 3*0.0833333 + 4*0.0833333 +
5*0.0833333 + 6*0.0833333 + 7*0.0833333 + 8*0.0833333 + 9*0.0833333 +
10*0.0833333 + 11*0.0833333

I would be interested in how to alter the routing myself, if anyone has
the information.  I looked at some of the configuration files but could
not immediately see how to do this.  I would like NO reduction on inputs.
It appears to have something to do with ttable routing and gain factors.

Using qarecord, this problem doesn't exist.  I looked at the code, but
again couldn't find where the input levels were maintained versus arecord
where they are lowered.

Thanks to anyone for information on how to do this.  I'm sure there are
a number of folks out there who have cranked up their volumes, only to
clip on the card, then lower them again, only to throw away perfectly good
signal.  But many of them may not realize that this is totally unnecessary.

More information about the Linux-audio-user mailing list