slimx line out question
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joeld100

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I just got my iRiver slimX today, and tried it out with my Grado SR60 phones. It sounds fine through the headphone out, so I tried them through the line out, expecting to barely hear them, since the line out is supposed to bypass the usual internal headphone amp. Lo and behold, I can hear them, though its slightly over half of normal volume.

However, when the volume is cranked to 40 on the lineout, it sounded like crap. Listening to Chemical Brothers' Under the Influence, after the first bass drop, you can barely here the person saying "under the influence" cause it is so distorted. However, I can plug in my logitech z560 speakers and it sounds fine at this level, and the grado's in the headphone out at 40 sound fine as well, albiet entirely too loud.

Why is it the lineout sounds bad at high volumes on these phones? Anyone else have experience with this? Thanks
 
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HighwayStar

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I'm sure someone else can explain this better than me, but I believe it has to do with the line out (pre-amp out) being designed to interface with amp in circuitry and not the load of speakers or headphones. Driving it to full volume with that type of load is probably causing the distortion, it simply doesn't have the power.
 
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dinosauract

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Highwaystar has it basically correct. The line out on your player is designed to be connected to an amp which might have an impedance of, say, 10000 ohms. Your powered speakers would have a similar input impedance. Generally, the higher the input impedance of an amp, or headphones, or whatever is being driven, the less current they will draw. (A higher input impedance does mean more voltage is needed for a given volume though, which is why high impedance headphones of a given sensitivity will sound less loud than low impedance phones of the same sensitvity).

The output impedance of the line out jack itself might be in the neighborhood of 100 to 1000 ohms. Connecting your headphones, with their less than 100 ohm impedance simply presents too difficult a load to the line out jack. It simply isn't designed to provide the current needed by the phones. This will result in high distortion levels and gross frequncy response errors.

In general you need a factor of 10 difference in input impedance to ouput impedance to avoid problems, and the higher the ratio the better.

The upshot of all this is that nothing is amiss in your gear. You just need to connect things as they were designed to be. No harm in playing around though, within reason.
 
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HighwayStar

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A-ha ! Now that makes sense, thanks for the explanation. I thought I had a handle (albeit small) on it, but it's great to know the reasoning behind it.
 
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joeld100

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Thanks for the reply, I feel much better about my gear
 
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millerdog

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I believe the slimx also has some sort of attenuator when you push the volume up. The corner boosts(on the EQ) are cut off at high volumes. Since the volume is controlled by the remote and affects the line out, you may want to check this out.
I have a slimx and use it with the line out via a JMT CHA47 with no problems.
md
 
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