After a serious delay, I finally found the time to perform the test whitedragem was suggesting. I copied samples of the tracks with “gaps” on a small (8Gb) USB key that I formatted in both FAT32 and NTFS. As I was expecting, the gaps were there in both situations, hence the fault is not caused by the USB key size or type of formatting.
Nonetheless, preparing the test prompted me on something that may elucidate the problem. All my downloads come from only 3 sources: Hyperion Records (CD quality or 96kHz/24 bit), Presto Music (CD quality or 96kHz/24 bit) and Linn Records (96kHz/24 bit or 192kHz/24 bit). When played-back on the Naim, the files downloaded from Presto never display the artwork whereas those from Hyperion and Linn always do. And now the punchline: all faulty tracks are downloaded from Hyperion and are in 96kHz/24 bit resolution! Which immediately reminded me the suggestion made by GadgetMan some time ago. Recapitulating, gaps occur always AT THE SAME PLACE in tracks, and only in high-resolution, Hyperion downloads (that do display the artwork). My hunch is now that it is actually an unfortunate combination of the coding of the artwork and the musical contents that “puzzles” the Naim, with the gap being the signature of the fact that the processor tries to recover after something that looks like erroneous data. Would something like this make sense? If so, the Naim specialists may try to look for possible interferences between artwork and music data. By the way, I even tried to turn off the display, but the gaps turned up in a disciplined manner at the usual places, hence it is something about the read data.
It wont tell you why those files play back with gaps but - pragmatically - transcoding (flac > flac, using dbpoweramp/whatever) might give you files that actually play properly. Maybe worth a punt.
Dear Naim aficionados,
Since after two month of idleness the thread will be closed, I think that it would be useful to draw some conclusions before this happens.
The thread was open for identifying the cause of some sudden gaps that the Naim Uniti Atom Headphone Edition produces during playback from USB, in certain tracks and at the same places. Several possible causes were proposed: the size of the USB key, the formatting of the USB, a too large size of the reproduced artwork – my tests did not validate any of these possibilities. Eventually, my observation was that gaps occurred in tracks downloaded from just one source and saved in high resolution (96kHz/24 bits) → this cannot be a coincidence. The fix proposed by AndyR was transcoding flac → flac, using dbpoweramp/whatever (this fix must still be checked). Because this gap occurrence does seem to have something to do with a coding-artwork interference, it might be interesting to also run the files that give me errors through Naim players that do not display artwork → if any of you may want to do this test, I am perfectly willing to share some of those files with you!
I thank you for your kind and knowledgeable reactions and I wish you all a lot of (Naim) musical delight!