I prefer the Kobicon. I have used it for years now with zero problems and the connection is still tight on my RSA amps. Also there is better separation of the signals with the Kobicon over the TRRS, less crosstalk.
A thump when you turn it on. I have a few daps that do that, but I don't even notice any longer. And when you put a card back in, I would guess the dap is programmed to scan the card. How would it know you have not added a song or that it isn't a different card? And why take the card out? The scanning is so fast now I that I don't worry about changing cards as I can start listening while it is scanning.
I enjoy the TS RP. I have them in NOS and a pair with very low hours so they are fresh sounding. The sound is different. I would have to compare them again but I would be happy with the 6SN7W. I also like the 76 with an adapter to use 2 per channel, since a dual triode tube is required.
I find the HD650, unless balanced, dull and veiled in comparison to the Pioneer. I have also found that the Pioneer need a lot of burn in. They were a disappointment at first and I thought I had made a mistake so I let them just sit and put them in the closet with a dap running for days. They evened out and sound much better and more balanced from lows to highs. I am using the micro Zotl 2 (7062 and 6SN7W tubes) as the amp with the Chord Hugo for the dac.
I find that with the comparison to my other phones, the Pioneer do an excellent job. I can clearly hear the difference in tubes I use, the changes in a circuit as it burns in and they do sound even better with then Whiplash Twau 8 braid cable. Very transparent with a solid bass foundation that seems to ride along with whatever is being fed to them. Great headphones for sure.
What I refer to is the wires connected to the output jack for the headphones. It isn't just the headphone input but there are also wires that go to the speaker output. More wires for possible RF and EMI pickup. Isolating the wires from the headphone output gets rid of any potential impact on the headphone circuitry.