I suspect the jack on the Clip+ is at fault. When a jack is going bad, sometimes unplugging and reinserting will temporarily fix the connection. Since the headphone works fine with other sources, it is not an issue.
Just one Head-Fi member's opinion, but your listening experience is seriously compromised when on an airplane or train, so don't expect to get the best sound out of any iem or headphone in those environments. Just live with a bit of compromise while on the plane or train, then enjoy better sound from your headphones when you're back in a quieter environment. I haven't traveled with mine yet, but I do think the Beyerdynamic T51 mentioned above has decent passive noise...
Amazon has deals today on various SanDisk products, including the 128 GB micro SD card (apparently a slightly newer version) for $99.99:
SanDisk is the only company making real 128 GB cards at the moment.
As it hasn't shipped yet, no one here has probably had a chance to try it yet, unless they were lucky enough to try a prototype at an audio meet. I have the Noble K10, and am looking forward to trying it out with the Mini M8.
I wonder if your AKG K545 is defective, the cable is not inserted completely, or you are getting a poor seal around your ears. The K545 is a bassier, more portable version of the K550, which some find too lean in the bass. Did you try it unamped?
If you want to use the DAC in the AK100, then yes, you connect the headphone out of the AK100 to the analog input on the Leckerton amp with a 3.5mm to 3.5mm cable. You can set the volume of the AK100 to maximum. I have used that combination a lot and it sounds very good. The AK does not have a dedicated line out, but as the volume control is digital, it doesn't matter.The DAC in the Leckerton is no slouch, but it isn't too popular on Head-Fi. You can get a short...