Does anyone know if the dock connector change when Apple upgraded from 5th to 6th generation?
They did, and unfortunately there's no adapter for it yet. You can see more information on the Apple support pages here:
My understanding is that the new iPod Nano likely won't fit with a number of older, existing devices.
I should also mention that although there's no adapter, it still has a standard Dock connector, so it'll work with your existing cables, etc.
I have a dock connector to 3.5 mm head phone jack that I use to connect to a headphone amplifier, using my 4th gen iPod I got an output. The 5th and 6th gen iPods would not produce an audio out signal using the connector.
What I determined is that pin 11 on the dock connector is used to enable audio out on the dock connector if pin 11 is grounded. I took a my dock connector apart and pin 11 was not connected. Determining which pin 11 is was difficult as the connector is quite small. After soldering a jumper between pin 11 and ground my 5th and 6th gen iPods can once again be used with the headphone amplifier.
It seem the the 5th and 6th gens check for the pin 11 being at ground before audio comes out of the dock connector, where as the older generations sent audio to the dock regardless. I bought the connector online — I went to the Apple store but they do not have a connector like that, otherwise I would have bought one of theirs.
I just got the iPod Nano 6th generation, and was able to plug it into my Altec Lansing IMT325 via dock connector without any problems.
So, I think the 6th generation iPod dock connector is not different from the 5th generation at all.
(The Altec Lansing IMT325 says on the box that it works with iPod Nano 3rd to 5th generation, which led to my original question.)