usb soundcard/ mic input has DC noise

December 7, 2010 at 16:18:30
Specs: Windows 7, Pentium Dual Core 2.3 GHz/ 1 GHz DDRAM
Please Help!

I run a modest DAW setup, on a Toshiba Satellite L510 [2.3 GHz Dual Core, 1 Gig RAM]. The onboard sound output [High Definition Audio] was ok, and the mic input was horrible [noise floor 65-55 dB!], as is typical with laptops, mostly. Since I use an entirely virtual studio mode of production, and I only input vocals for demos ... I bought a Creative SB Play [USB soundcard thumb-drive], as that's the best I can get here; [my locale here have never heard of M-Audio or Behringers!].

Funny enough, the noise floor is even higher now [41 dB], though the recording is now a slightly improved mess! [Soundforge's spectrum analyser shows me a large DC offset].

I have researched all forums. The best and only solutions by smart folks out there were (i) run on batteries, since the AC power is the cause, OR (ii) cutoff the ground on the AC power plug, or use a "3 pin-to-2 pin" multiplug/ adapter.

Sadly, for me ... NEITHER worked. My audio/ mic input meter shows that constant (and sometimes "lashing"] noise floor at 41 dB [even with my mic boost off, and mic level as low as 10% in the windows mixer].

I read one article by someone who was knowledgeable on electronics, saying something about adding capacitance across (?) the "floating" audio jacks on laptops. Now, I'm not that knowledgeable on laptop/ electronic circuitry ... and all I know is that there is large DC interference on my USB AS WELL!

Please help me figure out and fix this somehow. [My current location offers no expertise on such matters.] I really appreciate the help. Regards.

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December 7, 2010 at 17:23:15
Hi TMK, well as the old adage goes, garbage in garbage out. Creative Labs cards are great for gaming but as you have found out, they are horrible when it comes to professional recording. I ended up buying an M-Audio and couldn't be happier. If there is any way you can order a Behringer or M-Audio online I would highly recommend doing so. Even the Turtle Beach higher end cards will run circles around the Creative Labs cards.
Yes you could do the capacitor bridging and it will reduce the DC offset but it won't do anything for the S/N ratio.

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December 7, 2010 at 22:00:55
I have two different M-Audio USB audio devices both have better noise and range performance of the built in sound cards. Have you tried a series capacitor to isolate the DC component. Are you using a condenser or electret microphone?

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