If somebody is interested in a European Belkin PF50, my Silver one is for sale since I finally found a black one :) My PF50

i would try directly contact with Audio-GD

A huge improvement!!!!!

Superaps / Ultracaps have a VERY long life expectancy, if used correctly. They can easily cycled 1.000.000 times before esr rises to an unacceptable value, depending on your design. They have an INFINITE shelf life. One cycle contains 1x fully charging and 1x fully discharge. In hour...

Search at ebay

I think it also could be a good option to open V5i-D with a tool like a Dremel, remove the dip socket and solder new (modified) pins. To me it looks like the pins are soldered directly into the Dip socket, so you have to remove those pins first. See how it looks inside:

https://www.ebay.com/itm/Upgraded-version-Zishan-DSD-HIFI-fever-portable-lossless-music-player-AK4497-/273635649439?_ul=NL

I have 250gb spread over 500 folders, no problems at all unless i stress device with pushing buttons too quickly

All files in one folder?

Opa1612 doesn't seem a good contender, at least not for HP amplification. Whitepapers show a series resistor of 100 Ohm. To me it looks like it doesn't have shorting protection. http://www.ti.com/lit/ds/symlink/opa1612.pdf Why not using balanced output with AD8620? Works great, just need to...

When I received my Zishan, I charged it while listening and encountered same problem, it got charged only about 50%. After I switched it off and charged it, it went to 100%. Not sure if it was immediately or after a few times charging and discharging. Mine now charges to 100% even if listening...

Like said before, balanced output (with AD8620A) of Zishan 4497, has plenty power to drive HE400i. Not sure if stock OPA275 delivers same amount of power. I removed 4 resistors too, changes SQ in a positive way. Most tracks playing on volume level 26 to 27 gives more than adequate output...

HE400i sounds terrific on balanced output! They are available for USD179!!! https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F253238435384 Buy the Defean Lambskin angled pads at AE, they make the HE400i sound even better, more open and more sub bass.

i removed them and soldered wire on the pads

Graph about Vref from Arduino site, taken from AKM whitepapers:

the other cap values are correct, except for VrefH(L/R) to VrefL(L/R) Unit is deadquiet, no background noise.

I removed 4x10 ohm resistors, sq is definitely better, especially bass output is much better About the 10uF value for vrefh to vrefl (both channels), this was also in whitepapers of 4490 and 4495, values of 10uF, as well in whitepapers of evaluationboard of 4495, BUT in whitepapers of...

You are right! Also strange standard version has 22ohm resistors, just checked AD8620A datasheet, it has indefinite shorting protection, will short my 10 ohm resistors and try how it sounds with my HE400i and KZ-ZS10. Btw, have my HE400i balanced connected, sounds great! KZ-ZS10 sounds great...

Those 100uF caps are part of it's low pass filter Also VERY important, caps used for Vref, between VREFHL-VREFLL and VREFHR-VREFLR, they must preferably be 2200uF or higher value. I know there's not sufficiant room for high values, but must try as high as possible. In my previously build...

Does differential output of 4497 need coupling caps??? Very strange, will have a look at the whitepapers

You could damage the opamps, but I really think they aren't necessary. Be sure to connect your hp's before powering on Zishan. Don't remove the resistors, just solder 4 short pieces of wire on their top to bridge them, or, solder second smd resistor's on top of them (parallel)

Man oh man, how many times do i have to upload and post pictures of Standard version (the above is STANDARD) and Upgraded version..... Upgraded version has NO 4 electrolytics but 4 SMD caps, and i suppose these are bypass caps for psu and not coupling caps. In schematics it shows balanced output...