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Stereo cross talk in portable devices.

post #1 of 6
11/11/10 at 8:56am
Thread Starter 

Hi,

 

 

I am a portable device enthusiast. I keep an eye on all new smartphones out there.

The most exciting ones were released this year: iPhone 4, Galaxy S, WP7 devices...

 

   All of them suffer from high crosstalk issues when plugged with 32ohm headphones.

 

  All the info is based on measurements from gsmarena.com.

 

 

 The methods they use for testing

 

Measurements of the phones (scroll down a little to see a table ) link

 

 

Please explain ,why the stereo cross talk increases so badly when headphones are attached.

 

 

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post #2 of 6
11/11/10 at 9:42am

see http://focus.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slyt190&fileType=pdf&track=no

 

figure 6 & 7


Edited by xnor - 11/11/10 at 9:44am
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post #3 of 6
11/11/10 at 1:29pm
Thread Starter 

Thank you for information. Very nice graphs.

 

 

So how to interpret this? When one plugs headphones, he hears sound that is close to mono?

 

Why is LG so bad at stereo cross talk, it has dedicated amplifier and despite that it produces mono sound...

 

 

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post #4 of 6
11/11/10 at 3:00pm

Hehe, 0 dB would be real mono but I get what you mean.

(Side note: I listen to many tracks with crossfeed enabled which effectively increases stereo crosstalk to about -20 dB. Less stereo separation, less fatigue imo. :P)

 

The problem is that such devices aren't primarily designed to deliver the best audio performance into a wide range of loads. The designers have to make compromises.

(number of parts, parts cost, power consumption, size ...)

 

If volume is set to a fixed level and you decrease the load impedance (worst case would be some multi-driver in-ear with < 16 ohm), the amount of current will increase. The pdf describes why this also increases stereo crosstalk.


Edited by xnor - 11/11/10 at 3:11pm
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post #5 of 6
11/12/10 at 12:44am
Thread Starter 

xnor,                                 

 I got two points from your response

 

1. -20db crosstalk isn't that bad

2. Stereo cross talk increases as we decrease impedance at a fixed volume.

 

 

I believe that plugging higher resistance headphones should decrease stereo cross talk. I have HD25  on mind with 70ohm resistance...

 

Can you interpret the following crosstalk values:

 

-20db

-40db

-60db

-90db

 

               ?

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post #6 of 6
11/12/10 at 3:55am

Here are some files with pink noise: http://rapidshare.com/files/430363572/pink_r_mp3.zip or http://hotfile.com/dl/82209444/1704ee3/pink_r_mp3.zip.html

 

(bleeding from the right into the left channel)

 

-20 dB is clearly audible and certainly changes stereo imaging.


Edited by xnor - 11/12/10 at 3:52pm
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