Regarding my review on my Dell Latitude D620, I got a question from Robert about the performance of the audio output on the port replicator vs the line out on the laptop. He had read that the sound was pretty awful and wanted to know how mine performed. The quick answer is that he’s right… but my engineer in me can’t help quantifying it…
So after a little searching, I found this application called DSSF3. It has a 30 day trial, so I decided to give it a whirl.
After maybe 20 minutes or so, I figured out how to measure what I wanted. The software does WAY more than I need, but I was able to get a frequency response measurement from both the laptop audio jack and the D/Port audio jack.
For the tests, I simply took a standard male to male 1/8″ audio cable and looped back the audio out to the line-in port. The first plot below shows the distortion of the laptop jack.
Keep in mind that I’m sure the audio input is also a limitation. So these plots are really most useful in a comparative analysis.
Here’s the response I got from the D/Port jack.
As you can see, there is significantly more distortion in the low range, and this verifies what I thought I was hearing when comparing the two. It also seems the response curve is not as smooth with that hiccup at 1kHz.
So, basically, the line out jack on the port replicator really does not sound that great for playing music. I wouldn’t go as far as saying it sounds really bad, but I can notice a big difference, and I do not claim to be any sort of audiophile. Hope that helps.
Per the comments below, I also tested this “PC Speaker Mute” option and it does dramatically improve the quality of the sound when playing audio out of the jack on the docking station. I did not go back and do the above analysis, but to my ear, it sounds just as good as hooking directly up to the jack on the laptop.
A big thanks to Robert for pointing this out. Below is a screenshot of the where the volume control setting is (click for larger view.) To directly answer Kyle’s question, the PC speaker does normally sound when docked. However, if you have anything plugged in the jack on the dock, it mutes the speaker. But, when you additionally check, this setting, it improves the sound quality for whatever reason.