How do line outs from ipod dock connectors work?

[Wiggy Fuzz]

hi. just a question i thought i'd ask - specifically, how does an ipod dock connector out to 1/8 inch jack work?

i had always assumed the data coming out would bypass the ipod's internal digital audio converter, but to me something has to be converted if it's going to come down an analogue cable.

does this then, mean the audio is still being processed by the on board DAC, then? and if so, how does using a line out dock compare to a standard line out cable going out to a portable amplifier (using a cmoy).

just came to me while i was listening to the ipod without my trusty (rusty) amp, and i thought about what difference it would make if i went for a line out dock connector. i've seen some pretty nice (but expensive) ones for sale, and didn't want to really want to pay that price for them (just bought grado sr325i's. plug them into anything with a hole in

)

and if LOD's still use the ipod's dac, does that also count for those ipod music docks and dock to rca (i have a little cambridge audio ipod dock to rca i've decided to use with my stereo system). my system isn't anything high end, it's a 15 yearold hand me down from my dad, an old sony seperate high fi system, back in the days where it was all pretty much made of wood.

sorry if the answer's plain and obvious, but i just wanted to know for sure. i wear headphones everywhere, and currently go about with a metre long 1/8 to 1/8 connector, wrapped through my belt holes, and my headphone cable wrapped around my belt holes too. amp in one pocket, ipod in the other. i'm open to new amp suggestions, as long as they can be bought/imported to theuk.

thanks in advance

 

[Punnisher]

A Line out dock is simply a cable that connects to the bottom of the ipod. The analog signal in this cable is a fixed volume signal from the DAC in the ipod. Using this has several advantages:

1. The signal is a line-level signal, so you don't have to guess about the correct volume to set your ipod to. Just plug it in and that's it. No clipping due to higher than ideal volume.

2. A more pure signal. This is debated but many say that the signal bypasses the internal amplifier.

 

[billybob_jcv]

Punnisher is correct - It is not bypassing the DAC - the line-out is analog. It's essentially the equivalent of having a pair of white/red stereo audio jacks. The ipod volume control does not affect the line-out signal, so you need to have a volume control on your amp.

I suppose it's theoretically possible to bypass the DAC if you interfaced with the USB port pins in the dock connector - but I'm not aware of any headphone dac boxes with that capability. I suspect at that point it would just be easier to have a laptop with iTunes on it...

 

[ClieOS]

Here is my understanding of how things work. If it is wrong, please point out. Thanks.

 

[Wiggy Fuzz]

ah right, i see. well, taking your points into fact i tried plugging my headphones direct into my ipod dock

and true the volume was presumably disabled on the ipod.

nice - is there anyone who sells (and ships) an LOD cable to the uk? i'm interested.

 

[swayne]

You can get them from Meier Audio and iBasso and Play.com amongst others.

 

[Wiggy Fuzz]

oooh - ibasso amplifiers look nice. are they nice? they're much cheaper than the tomahawk, too, which is good. don't like the 5 aaa batteries, though. it'd be like reloading a shotgun.

dac one looks nice though.

 

[swayne]

I like my D3.

Going from the ipod headphone socket to a line-out with an amplifier is a big difference.

 

[qwertgfdsa]

Quote:

Originally Posted by ClieOS /img/forum/go_quote.gif Here is my understanding of how things work. If it is wrong, please point out. Thanks.

Thanks for the great pic first.
I have some questions, why iMod 5.5G still can be listened from the phone-out?
and according to the pic, iPod doesn't seems to have a true line-out, so why people always says a dock from line-out improve the SQ a lot?
If you turn to the maximal volume, is the phone-out sound different from the line-out sound on iPod?

 

[Pale Rider]

Quote:

Originally Posted by billybob_jcv /img/forum/go_quote.gif I suppose it's theoretically possible to bypass the DAC if you interfaced with the USB port pins in the dock connector - but I'm not aware of any headphone dac boxes with that capability. I suspect at that point it would just be easier to have a laptop with iTunes on it...

This raises an interesting possibility. I know there are a few iPod adapters--at least one by SendStation, I think--that present USB interfaces to iPods. Anyone know whether those are just for power or whether they output a signal? My assumption is that they are just a power interface, not an informational one.

 

[ClieOS]

Quote:

Originally Posted by qwertgfdsa /img/forum/go_quote.gif Thanks for the great pic first. I have some questions, why iMod 5.5G still can be listened from the phone-out? and according to the pic, iPod doesn't seems to have a true line-out, so why people always says a dock from line-out improve the SQ a lot? If you turn to the maximal volume, is the phone-out sound different from the line-out sound on iPod?

I drew the graph based on RWA's description on their website. Maybe they didn't disconnected the connection b/w DAC and amp in the 5.5G iMod after all? I'll revise the graph later.

Even if normal iPod line-out is not a true line-out, it still bypasses some of the cheap caps / circuit that used for controlling volume and such (where most of the SQ degradation happens). So theoretically it should still be better than headphone-out in max volume. That's my understanding.