The people in the video from left to right:
Sato Hiroaki - Walkman lead sound engineer
Matsuzaki-san - Walkman electrical design and sound engineer
Pierre Nakano - Drummer of band "Rin Toshite Shigure"
e-earphone staff (he didn't mention his name)
Note: I picked out the parts where they talk specifically about the hardware of the ZX-507, leaving out discussion of stuff like streaming service (where they plug Sony's own hi-res Mora qualitas service), or Bluetooth headphone discussion regarding the choice of being able to control volume on the device rather than sending a straight signal to the Bluetooth headphone
* Pierre Nakano says his current earphone of choice is the IER-Z1R (side note: I've met Pierre-san before at a Just ear owner's secret meeting - needless to say, he is a Just ear owner and is a huge audiophile)
* Sato-san and Matsuzaki-san (with some egging on by Pierre-san) said they use songs by the famous female group Perfume as testing song when making Walkmans, because their songs are hard to reproduce faithfully as it puts a lot of strain on the power delivery of the system, without a stable and strong power delivery circuit it won't be able to get the deep bass (down to 30Hz) and the snappy kick drums attacks out of their songs
* Using Android needs a fast CPU, and the fast clock of the CPU generates much more noise inside the device, so they installed a full copper shield milled from a thick slab of solid copper around the digital circuitry. In the ZX-300 a similar shield was installed but it was pressed from thin sheet copper which had gaps in it, so the shielding in the ZX-507 is vastly increased.
* completely separate analog and digital circuitry - even the power is completely separated first before powering the components
* S-Master HX actually has 6 channels - 4 is used for the balance output, and 2 is used for the single end, and as we know the capacitors used for the two outputs are different
* They mentioned you can use DSEE HX and the Equalizer when watching video on the ZX-507 (so I'm taking that to mean the upsampling and equalizer is system wide)
* Moving the charging port to the side was the ensure the wireless antenna at the bottom of the device would not be obstructed to ensure best wireless connection performance. Whereas the height position of that port in relationship to the side of the device was taking into account the best wire routing for the battery circuitry as the device is being charged with USB to have the least interference during playback
* The balance output uses the same capacitors as those found in the DMP-Z1
* All the components for the single end circuitry must be confined within a height of 2mm, they still managed to double the capacity of the capacitors used in it compared to those used in the ZX-300 for an improved low end performance
* They use their gold-infused solder which was used in the DMP-Z1, and the formula was Sony developed. Also many of the soldering in the Walkman for certain components like the headphone jacks, connectors, and battery is still done by hand and they try to avoid soldering the connecting pins on the parts directly onto the board as much as possible (note: this is because if you solder parts like the headphone jack directly onto the board using the package pins, they have no give which when dropped will snap and break, the floating connection is what Sony use to introduce tolerance for shock absorption)
* The material used for the PCB was especially selected for its performance on being able to handle high frequency signals which is not usually used in audio products
* they make lots of prototypes with each only changing a part of the system to analyse what effect the change has, before bring everything together
* as we know the recommended burn-in time for the capacitors in the Walkman is 200 hours, they actually play the prototypes normally with normal music connected to normal headphones at each point when testing for the changes, and don't use any special "burn-in" device to speed up the process nor use burn-in signals like wave/noise tones
