This is probably irrelevant, but worth to try. Have you tried using a different sdcard on the X3?

I'm sort of expecting a different answer. But now I really have to checkout an X3ii :confounded:

Nice one! Have you tried clipping it on your shirt? Is it too bulky for it? The thing is, clipping on my shirt is the best way for me to get rid of any cables that may tangles.. also the most comfortable way using it while moving around. Colorfly C3 is 100g and I thought it would be too heavy...

You sir, are my greatest inspiration of April 2019.

Thank you for the research, it does seems that a perfect lipo replacement for Colorfly C3 would be a 1000mah 434350 3.7v lipo. https://cdn.head-fi.org/a/10249635.xlsx But looking for a fresh lipo battery in my country is a pain, except for some common sizes. So I agree that getting a regular...

Well C3 sounds very flat and "correct". Almost the same signature out of my DACMagic. I assume the Westone sounds very flat? If you want coloring, get V colored IEMs such as VSonic or as suggested, get an amp to do so. I myself found that it drives GR07BE pretty well on moderate volumes but out...

  Yeah the power issue is just a guess anyway. I really wanted to put the capacitor hack but couldn't afford losing the one and only C3 I had lol

Well it is sporadic in my Evo 128GB. Once every 5, 10 minutes, short ones, 2 seconds-ones, 3 seconds-ones. Yet no such issue at all with both Evo 64GB I owned. I don't think seek reading a memory card will require more power, though. It may not like spinning a disc faster or something like that...

As my guess is power issue, probably undervoltage or undercurrent due to the demands of some microSD cards, I am always thinking whether soldering a capacitor on the microSD slot power pins would cure the issue.   Apparently we have something here: http://forum.arduino.cc/index.php?topic=58643.0

  I think at this point you better stick to any well-tested microSD cards discussed in the thread. Get an Evo 64GB and you'll be fine.   Audio quality will always be the same but that buffer underrun stutter is what messed it.

  False hope. What a dissapointment      You're getting buffer underrun on a 32GB microSD card??? In that case I'm pretty sure this is some kind of power-related issue.   Switch to Evo 64GB and I'm sure the issue will go away. It's just that we haven't tried any "working" 128GB yet. If...

Custom version 1.4??? Where di you get that? Firmware alone could possibly fix the problem, really. I'm excited now 

  Wait, how do you format it in C3? I'm in firmware 1.00.00.06 and couldn't find any menu to format an SD card?   I bought mine from a local seller.   Hey can you post your C3 serial number, is it the 8GB model as well? I can always sell this one and buy another one from ebay.

  Nope, I had bunch of new songs that I've listened over and over again with both SD card and "Interal" memory and didn't notice any difference. I think C3 don't have such issue.     Well we don't have any option other than FAT32 right? I formatted it using the GUI Format tool, tried with...

You sure no issue at all?   I've tried two different codes of that Evo 128GB: 1) Model: MB-MP128D Model code: MB-MP128DA/APC 2) Model: MB-MP128D Model code: MB-MP128DA/EU   Both had the exactly same problem. Not sure with MP3, but happens with FLAC 16/44 and WAV 24/44.   Which exact...

  Samsung EVO 128GB causes buffer underrun on my C3, in which I don't understand why. The EVO 64GB is perfectly fine.   Btw the link your posted seems a fake EVO 128GB ones, I think the price is too low. I bought mine like USD85 or so.

 I ordered the GR07 BE from him.   Took 2 weeks before it's traceable with the postNL I think. Another week or so for the full delivery. And I'm in Asia!   Btw the 4GB C3 seems to have different LED backlight color. Wonder if any of the internals are different. I am pretty sure my 8GB C3...

    I can confirm that the Colorfly C3 supports 128GB microSD cards. Testing it with Samsung EVO 128GB UHS-1 Class-10. Of course, formatted with FAT32.   In fact, I just finished playing from last bits of sound from a file within the 126GB-ish region in the card. So both the C3 and the...

  C3 is not sorting it, it just directly reads the basic FAT32 filesystem entries.   The only true way to sort is to sort file the entries in the FAT32 table externally, with Anerty's DriveSort. I've also used it for the internal storage and it works very well.   This confirms my suspicion...