[LAU] What audio interface to use for a Linux-powered surround?preamp?

Fons Adriaensen fons at linuxaudio.org
Tue Dec 20 23:44:30 UTC 2011


On Tue, Dec 20, 2011 at 06:24:13PM -0500, gene heskett wrote:

> On Tuesday, December 20, 2011 06:22:02 PM Fons Adriaensen did opine:
> 
> > Mmm. An IP3 of 40dB means that at e.g. -10dB (already high as
> > an average level), IM is at -110dB. That is nowhere near to
> > 0.5%...
> 
> Picky Fons  :), but I swear I can hear it, or maybe I stated the 
> terminology wrong?  Or have I been listening to SSB radios too long?

:-) Have you ever listened to AM radio on headphones with
LSB in the left channel and USB in the right one (and the
local oscillator synced to the AM carrier) ? It's absolutely
wonderful. All the interference is stereo, and the AM station
is exactly in the center which makes it very easy to ignore
the interference.

Regarding IM distortion, I've found that in many cases the
cause is not the active analog electronics but non-linear
contact resistance in switches, pots and faders. A few years
ago I did a routine check on my analog mixer. It had horrible
IM on one of the channels wired to the soundcard. And the
reason was simply that the mic/line switch on that channel
hadn't been used for years. Just toggling it a few times
made the distortion go away...

Ciao,

-- 
FA

Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.



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