Subject:SNR level?

Posted by: Jovi

Date:4/11/2003 7:38:49 AM

Hi,

I have a question about my soundcards noisefloor. When I press the monitor button in the recordwindow without anything connected to my soundcard (audiophile 2496) the meters shows around -82dB. Is this the noisefloor of my soundcard?

Subject:RE: SNR level?

Reply by: Rednroll

Date:4/11/2003 10:13:39 AM

Yes. But having nothing connected might not be a good scenario, depending on how the sound card was designed. Some sound card inputs, with nothing connected to them may be normally connected to Ground, therefore the input is very near to 0 volts and you would therefore see only the noise floor of the electronics in the VU meters. When you plug an audio signal into these cards the ground connection is broken and the audio passes. Some sound cards have floating inputs, meaning they're not connected to anything/ground until you plug something into them. The floating inputs will pick up other noises, like computer fan noise, EMC, radio broadcasts. You will therefore see all these signals on the VU meter indicator, but they might not likely be there if there was something plugged into the inputs.

If you really want to see the true noise floor of the VU meters, you need to plug some connectors into the sound card inputs and then connect all the wires to the computer case, thus grounding all the inputs.

BTW: -82dB is good.

Subject:RE: SNR level?

Reply by: MJhig

Date:4/11/2003 10:25:19 AM

My Audiophile bounces between -82 and -84 while connected to my mixer powered down so you may be seeing the true noise floor.

MJ

Subject:RE: SNR level?

Reply by: Geoff_Wood

Date:4/11/2003 8:32:22 PM

With nothing plugged in, the inputs may be floating which will give you a few (or 10) dB more noise that properly terminated or shorted to ground. Easiest to test with inouts shorted (if the soundcard doesn't automatically do this with no plug in). But for scientific level reading, inputs should be terminated with a resistor of the specified input impedence.

-82dB sounds a bit high for a 24/96 spec card - my ancient TB Pinnacle does better than that, and that's 20/48 max . Try removing any internal CD-ROM audio cable ( read CDs 'digitally' in playing apps), and slotting the card as far away from others , especially video, as possible. Also keep drive cabes away from soundcard and ensure an adequate capacity PSU.

geoff

Subject:RE: SNR level?

Reply by: Iacobus

Date:4/12/2003 4:12:57 PM

My Audiophile bounces between -85 and -90. Could drivers have anything to do with it too? (I'm no audio engineer but I'm absolutely curious nonetheless.)

Iacobus

Subject:RE: SNR level?

Reply by: Rednroll

Date:4/14/2003 9:48:30 AM

"My Audiophile bounces between -85 and -90"

Do you think just because you can see noise at -85 to -90 that this is a problem? A CD which has NO electronics in it, have a noise floor of -96dB. This is pretty quiet. Noise at these levels are pretty negligible. When you start to see noise around -45 to -30dB ranges....then you should be concerned.

Subject:RE: SNR level?

Reply by: Iacobus

Date:4/14/2003 1:52:08 PM

Oh, I'm not concerned at all. I was just wondering as my readings were a little different from mjhig's. I'm quite content with it. :o)

Iacobus

Subject:RE: SNR level?

Reply by: Jovi

Date:4/14/2003 4:22:09 PM

First of all I want to Thank you for all your posts!
-85 to -90dB shown on the input monitor meters in SF for an "Audiophile 2496" sounds really impressive! When i posted this topic I got -82dB but after moving the PCI card from SLOT1 to SLOT6 on my ASUS TUSL2-C motherboard (far away from AGP and NIC now in SLOT1) the noisefloor dropped down to -85dB. The RMS level with no signal @ 24 bit 44.1 khz measures around -97dB. I guess this is the best i can do with this card, and I guess few people will mention noise in my recordings as their first impression. Thanks again peeps!

/J

Subject:RE: SNR level?

Reply by: Geoff_Wood

Date:4/15/2003 6:02:10 AM

.... especially considering the snr of you room, etc, is likely to be more like 60dB.

geoff

Subject:RE: SNR level?

Reply by: Geoff_Wood

Date:4/15/2003 6:02:48 AM

Jovi sed : " and I guess few people will mention noise in my recordings as their first impression. "

.... especially considering the snr of you room, etc, is likely to be more like 60dB.

geoff

Subject:RE: SNR level?

Reply by: Jovi

Date:4/16/2003 2:10:46 AM

He He, funny how easily some things can be explained. Damn true! Who need's -100dB SNR when your room is filled with 40dB of airconditioning, PC's and maybe a even neighbour playing the drums. :)

/thanks, johan