Audio Y Splitter Not Splitting Signal Properly

[jeffbruce]

Hi all,

I have a setup where I take a stereo audio track created in Matlab (L track contains signal, R track contains noise) and present it out through the audio jack on my computer using a 1->2 RCA cable. This RCA cable should split the digital stereo track into 2 separate analog mono tracks for further processing. When I silence one of the analog cables (by unplugging either the L or R) in an attempt to either completely remove the signal or the noise, what I find is I'm left with a track that contains both signal and noise. If I unplug the L track, the remaining track tends to have louder noise than signal, whereas if I unplug the R track, the remaining track has a louder signal than noise. This suggests to me that the signal is somehow being premixed before splitting the stereo track into 2 analog mono tracks. I'm fairly certain the problem isn't the 1->2 RCA cable because I've tried using a simple 3.5mm headphone splitter instead and it does the same thing. I am working on Windows 7 with a Creative SB X-Fi sound card with the following details:

Driver Provider: Creative
Driver Date: 7/7/2010
Driver Version: 6.0.1.1348
Driver Signer: Microsoft Windows Hardware Compatibility Publisher

I would really appreciate any ideas for why the signal is behaving this way.

Cheers,
Jeff

 

[sreten]

Hi,

Why are you sending two tracks, one noise only to a mono output ?

I don't understand you post. seems like you've got autogain
on your inputs which ups noise if the input is unplugged.

rgds, sreten.

 

[sofaspud]

...present it out through the audio jack on my computer using a 1->2 RCA cable. This RCA cable should split the digital stereo track into 2 separate analog mono tracks for further processing.

I would expect a 1->2 RCA cable to behave pretty much as you describe.

I've tried using a simple 3.5mm headphone splitter instead and it does the same thing

A stereo male to 2x stereo female, or stereo male to L and R female?
If you're fairly certain the signal isn't being summed by the cables, that leaves the computer itself as culprit.

 

[Frank Berry]

You should check the setup of your sound card.
Make sure that the output is set for stereo speakers.
Disable all effects.

 

[wwenze]

Run X-Fi control panel, disable CMSS.

 

[revboden]

yeah, your dealing with some kind of spatial enhancer. turn off all effects

 

[Enzo]

And if your audio card has any mixer controls, make sure both L and R signals are panned all the way to the extreme L and R setting.

 

[counter culture]

The relative levels are critical as regards deciding what is going on, but 3.5mm stereo jack sockets (and plugs I guess), have an intrinsically high level of crosstalk, IIRC. You can probably find the figures on nwavguy's blog.

 

[jeffbruce]

Problem Solved

Thanks to everyone who responded!

The problem was that the sound card was set to Game Mode, so I disabled all sound blaster effects.

Cheers,
Jeff