[gerG]

There is still some discussion on the topic of output quality from the headphone jack vs the line out. I decided to do a couple of simple listening tests to convince myself one way or the other. Although the results are significant and relevant to my ears, they are subjective, and I encourage anyone interested in the difference to try the experiment for themselves.

First I connected both outputs from my minipod to a headroom switch box for an A/B test (pic below). I used identical mini to RCA cables. I matched the volume of the headphone output to the signal output (it is slightly below max). Switch fed the analog inputs of a Grace 901, which drove the Ety ER4S.

I had intended to do the test blind with random repeats. However, the difference was so apparent that it became pointless. The line out had better clarity and dynamics overall. In comparison the headphone out sounded out of focus or diffuse. Acoustic guitar had a sort of reflected off a wall sound through the headphone out, but became clear and distinct from the background from the line out. Bass kicks were cleaner and had better impact and resolution from the line out.

Part B was a check for dynamic compression. This is not the most rigorous approach, but it is easy! Just connect the headphone out of the player to the input of an amp with a volume control. Set the player (ipod, etc) volume to max, and set a reasonable listening level on the amp. Now turn the player down while turning the amp up. If you have enough volume pot, and don't run into a noise floor, you should start hearing lost dynamics on any device with digital volume control. If the device upsamples, there will be a range before compression sets in. I perceived it beginning somewhere between 30% and 40% on the ipod scale. It was especially apparent in drums and percussion, and also in the bite of picked guitar strings. From this one I conclude that listening above 50% scale on the control should keep me out of compression when I am listening straight out of the HP jack.

gerG

 

[hassy500]

Dear Mod:

Please sticky this article. Thanks gerG for the info. It sure is easier tweaking a new device (4G 20GB Ipod) when you have such an information base.

 

[KenW]

Excellent! I appreciate that. You've either saved me some $$ and/or forced me to find a more portable solution for the line out on my Karma. Thanks for your efforts.

 

[jpr703]

Great write-up. Thanks!

 

[raisin]

Thanks for taking the time to clear up this recent tempest in a teacup.

 

[trevorlane]

interesting, i second the thanks.

 

[bangraman]

Interesting. I'll run a test with an iPod (normal)

 

[gerG]

Hey guys, thanks, and glad the info is of interest. I suspect that others have done similar tests, but I don't know how much has been posted.

I did some more listening, with different headphones. I ended up with the DT250-250, and reached the same conclusions, plus something interesting. Switching from the line out to the phone out seems very much like switching on crossfeed, but not necessarily good crossfeed. There is also something going on in the deep bass, which I am so very fond of. The DT250 can produce the kind of deep bass that makes me think I am feeling it in my body. I happened to listen to a track with just that effect, flipped the switch, and it was gone. Switched back to the line out, and it was back. I need to spend some more time making sure it wasn't a cable or something. It was very much like dropping in a rumble filter that is set just a bit high.

Quote:

Bangraman wrote: I'll run a test with an iPod (normal)

By all means! It would be good if a normal person did this test.

gerG

 

[raif]

Does anyone have any good links I can use to do some research on the whole issue of compression with digital volume controls?

Also, how can you tell audibly?

Most of my equipment centers around computer sources and I am trying to understand the whole thing completely.

 

[duff138]

what's that cable you are using that allows you to use the line out. I was going to buy the dock so I could use the line out. I had not seen a cable that would allow me to use the line out. where did you get that?

 

[Oink1]

That particular one is the SikDin You could also use the PocketDock lineout.

 

[fr4c]

Quote:

Originally Posted by duff138 what's that cable you are using that allows you to use the line out. I was going to buy the dock so I could use the line out. I had not seen a cable that would allow me to use the line out. where did you get that?

mini-mini cable is what you use.

 

[sno1man]

Very interesting test. If what you found holds true for the other pods, then the dock looks much more useful.

It does though make me wonder about the FM adapters such as the Griffin iTrip. I.E. it uses the headphone out so the quality might not be what it could be. Of course it's possible that the FM transmitter drops the quality enough that it doesn't matter......

Anybody aware of any FM adapters that use the dock connector instead of the headphone jack?

I have heard of something called a podfreq(???) that supposedly docks with the ipod but I have never actually seen one.

 

[fr4c]

if this really is the case, then maybe its more of a reason for me to get a pocketdock or a sikdin for my portable rig. and i thought for a second there that there wasnt too much of a difference between headphone out at max volume and line-out.

 

[Oink1]

Quote:

Originally Posted by fr4c if this really is the case, then maybe its more of a reason for me to get a pocketdock or a sikdin for my portable rig. and i thought for a second there that there wasnt too much of a difference between headphone out at max volume and line-out.

It's SO much better using lineout (IMHO) Get a lineout device - what have you got to loose?