On Sun, 15 Jan 2006 14:50:01 -0800, John Miles
wrote:
In article ,
says...
Sorry, all sound cards that I know of are AC-coupled, with a roll-off
I've never studied them, but I would expect this to be the case. And even
if it were not, I can't imagine why the DAC would be designed to support DC
Hmm. I'm not sure how to design one that doesn't.
Usually, all that's necessary is to locate the output coupling
capacitors on the sound card and bridge them. This may be easier with
older Sound Blaster 16-era sound cards, before they all went to SMT.
IIRC, at least some of the Crystal/Cirrus data sheets for ADCs (and
codecs) indicated that there was a 3 Hz lower frequency limit,
apparently due to some DC offset drift compensation circuitry on the
chip itself.
Even if the sound card is AC coupled with a capacitor, various diode
clamping tricks can be used (as in clamping the sync tip to a known DC
level in video equipment).
Paul OH3LWR