What's the advantage of outputting audio through the line out vs. headphone out?

January 18, 2005 7:43 PM

Other than the advantage of never having to adjust the source volume, what's the advantage of outputting audio through the line out vs. headphone out? [...]

I've seen the iPod dock refurbished at the Apple Store and have been thinking if it is worth it or not. It just does two things: stand the iPod up at a slight angle and provide a line out. I'm not an audiophile and I could never tell if there's a noticeable sound difference between connecting a portable CD player at 75% volume or straight through the line out.

posted by sammich to Technology (9 answers total)

Every amplifier stage reduces the quality, since it doesn't reproduce the waveform perfectly. So if you're amplifying it later, like in a receiver, you don't want to amplify it in the computer/CD player/iPod.

That's the theory.
posted by smackfu at 7:52 PM on January 18, 2005

The audio going through the headphone output may undergo an additional step of amplification (for loudness) and/or attenuation (for volume control), potentially coloring the sound or adding noise. In your case, count your blessings. If you really can't tell, ignorance is bliss, right? I'd look more into the convenience aspect of the dock than the sound, then.
posted by zsazsa at 7:56 PM on January 18, 2005

(You do run the risk of audiophiles annoying you by saying "oh my GOD, why aren't you using line out?" though.)
posted by zsazsa at 8:03 PM on January 18, 2005

Audiophiles don't use iPods for the audiophileness. The line out is strictly for connecting to a device that will be doin' the amplification for you (read: powered speakers or a stereo).

That's it.
posted by basicchannel at 8:52 PM on January 18, 2005

Well, I think the audiophiles would be saying "Oh my GOD, why are you using MP3/iPod" and then they might jump off your condo's balcony to get away from the horrible noise... If you are using the iPod, you aren't worried about a line out.

Along with smackfu's point, the line out will be adjusted to the best possible volume for the internal electronics (to maximize dynamic range, and minimize noise).
posted by Chuckles at 8:56 PM on January 18, 2005

The headphone out on some devices, if improperly adjusted, can overdrive the inputs of the connected amplifier. You would notice the distortion, and not like it.
posted by Jack Karaoke at 9:17 PM on January 18, 2005

fwiw, I've used a pre-line out ipod for a couple years, mostly hooked up to speakers rather than with headphones, and I have had no problems.
posted by Utilitaritron at 9:23 PM on January 18, 2005

More to the point, the headphone output expects to be driving headphones (typically in the low hundreds of ohms impedance, I found 'phones rated for 100-250 ohms in a quick Google search) while a line input is typically 10,000 ohms or more (I found 13,300 for unbalanced line inputs on a mixer on a quick Google search). This mismatch can theoretically cause a loss of frequency repsonse, although in practice I've never noticed one. If you're picky though, use the line out to connect to line in.
posted by kindall at 9:57 PM on January 18, 2005

The sound from the headphone jack is slightly muffled and weird compared to the clean sound from the line out, though you might not notice. Also not having to turn the volume right up for line out also saves your ears from plugging headphones back in before you've turned it down.
posted by cillit bang at 10:40 AM on January 19, 2005