I have now had a chance to listen to my new P4. Initial impressions: - A very clear, detailed sound with a good soundstage and impressive dynamics (for a portable), - On the bright side of neutral with the stock op-amp configuration. Overall, it seems like good value for money (1,499 RMB, about GBP 150). So far, I have been using it primarily with my GR07s (for which, after all, I bought it!). The op-amp configuration is still stock (and will stay so until it is run in and I am familiar with the sonic signature), but I have switched it to low gain (otherwise the difference between inaudible and deafening on IEMs was about one degree on the volume control! I have also noticed that the sound quality has improved after this move, suggesting that either the impedance matching on low gain is better, or that the volume pot is not performing at its best at very low levels. I tried it (on high gain!) with my HD600s, but was disappointed. It drove them, in the technical sense of the word, but the sound was flat and lifeless. Given its form factor and price, this wasn't entirely surprising, though. I hope that it will perform better with my new FA-003s (waiting for me back in the UK), as these are easier to drive and have a low impedance - and will figure in my "hotel room" system. As I bought my P4 here in China, it shipped without English instructions. I have downloaded a very basic manual from iBasso's website, but there is very little information of op-amp rolling (other than an inventory of what is in the box). Is there a "beginner's guide" available to prevent me from doing something stupid? I have read that at least one contributor has already dispatched his P4 to the hereafter by plugging the wrong chip in the wrong socket..... Also - what is meant by a "static-free environment"? Should I wear an earthed wrist-strap when handling the ICs? Do I need a special insertion and removal tool? Finally, I have noticed that some of you recommend op-amps which are not included in the package. Can I obtain these from RS or Maplin, or are there specialised sources for these?