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Why does line out have better SQ?

post #1 of 11
6/13/10 at 10:49am
Thread Starter 

what makes it sound better?  I'm looking for an answer that connects sound and hardware.  I already know what line out does, and I am still not sure how it makes better sound.  I am looking for something that answers that.  Line out bypasses certain components or answers of that nature does not explain much to me. line out bypasses this, so therefore it sounds better?  You see, that logic does not work so well with me, there is something missing in the middle(like an explaination). I need to know why bypassing is producing better sound.  Thanks.

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post #2 of 11
6/13/10 at 11:25am

It's my opinion that all amplifiers, whether internal or external, add some coloration to the sound.  The best amplifiers add the least amount of coloration and the worst amplifiers add the most.   If we were to take the signal directly from the internal player's DAC and bypass the internal amplifier we can get a cleaner signal that avoids the internal amplifier's coloration. 

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post #3 of 11
6/13/10 at 11:28am
Thread Starter 

What is colorization you speak of?  It sounds very vague, can you explain to me in terms of what the colorization does to the signal?

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post #4 of 11
6/13/10 at 11:33am

Coloration can be poor frequency response, not flat, accentuation at certain frequencies.  What you hear will not be true to the source material but changed in some way.  An audible change.

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post #5 of 11
6/13/10 at 11:56am

coloration is used to describe a number of things

 

distortion

changes in the frequency response

etc..

 

the best explanation i can come up with is this

 

once audio is converted from digital bits to an analog signal every component that signal passes through can affect that signal some components affect the signal more than others and in different ways... some good, some not so good

 

the internal amplifier on most devices is designed to be functional and cost effective often sacrificing sound quality and power

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post #6 of 11
6/14/10 at 12:13pm

 

Impedance loading has the potential for variable SQ, although in most good designs today, this is not an issue. Sometimes in the portable arena you have the output of the line out controlled by a potentiometer (e.g. µDAC and the Pico Amp/DAC). These typically range between 10K - 100K. SQ on these devices have the potential to change due impedance loading mismatch, resulting in FR aberrations. If you use a device with variable output on the RCA's, make sure you run it as wide open as possible to avoid impedance load mismatch. 

 

The other problem with variable outputs is that an "op amp" (typical source of our portable DACs and amps) output might overdrive the load input. Many op amps are designed for line level output (~2.0v), but some produce a lot more. Again, this is not normally an issue, but it's something to be aware of. 

 

In most cases, the load end of the chain is designed with 2.0v input in mind, or a little more. Using a fixed output eliminates mismatches between the source and load, minimizing SQ variability. 


Edited by Rdr. Seraphim - 6/14/10 at 12:20pm
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post #7 of 11
6/14/10 at 12:21pm

Great response Rdr. Seraphim.  I knew that (I once blew a home amp doing just what you suggested not to!) but I'd never thought of it terms of portable amps.  Good reminder to be careful in the future!

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post #8 of 11
6/14/10 at 12:21pm

The way I see it is that the amp inside an ipod is not going to be as good as an external amp, so it is best to bypass it. The main reason why I say that is because, as I experienced yet again to today listening to various headphones out of an ipod in a shop, the ipods amp is limited in its power. That is due to the compromise of battery life and also keeping Apple safe from lawsuits from people damaging their hearing. 

 

When I say power, I don't mean the ability to drive all headphones at ear-splitting volumes, I mean the ability to drive headphones to the full potential and get the most of of their detail, clarity and dynamics by making the sweet spot of volume control more accessible. My ipod Classic does not bring most of my headphones to 'life' as my amps do. The ipod's amp is a compromise and plays it too safe and robs the music of some of its 'life'.

 

So for that reason, IMO bypassing the ipod's amp is better for sound quality.

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post #9 of 11
6/14/10 at 12:35pm

BTW High_Q, from your profile I see that you are a double-E (EE)? Power? Computer? Signal? Transmission? How long in the field? 


Edited by Rdr. Seraphim - 6/14/10 at 1:09pm
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post #10 of 11
6/14/10 at 1:52pm
Thread Starter 

I've just recently graduated with BS in EE.  I am interested in RF circuits, but I will be working in a different field.  I hope to get a masters so that I can learn more about RF technology.  


Edited by High_Q - 6/14/10 at 1:57pm
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post #11 of 11
6/14/10 at 2:31pm

Congrats on your recent EE High_Q! And best wishes on your continued education. 

 

Hope we've helped with this threads discussion!

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