Sound gaps when playing flac files from a USB source on Uniti Atom Headphone Edition

Dear forum users,

I recently purchased a Uniti Atom Headphone Edition – we are really impressed by its performance.

However, I noted that sound gaps occur when playing back SPECIFIC flac files (albums) that are stored on a USB device. The gaps consistently occur at exactly the same points in the relevant pieces. I noticed gaps in both CD resolution files and in high-resolution (96kHz/24 or 32bit or 192kHz/24bit). I standardly use a brand-new 512GB SSD drive, but I copied the files showing the issue on USB keys of 16GB or 64GB, the gaps occur at the same points. Strangely, when streaming via Bluetooth the relevant files from the SSD drive connected to my laptop (Windows 10, VLC player) the pieces are flawlessly reproduced. To conclude with, the same files can also be played back without error on our Denon AVC-X4700H – in fact, I never experienced this flaw on our Denon in more than 2 years of operation. Please note that all files are downloaded from professional platforms (Hyperion, Presto, and the kind), thus are not self-generated and the firmware on the Uniti Atom is up-to-date.

Did you ever encounter this issue? If so, do you have a solution?

I thank you in advance for your help!

Anything to do with “Gap-Less” playback?

Hi, as a solution architect / data engineer I can honestly say there is no real digital signal. People do like to argue this point but I have been testing and writing stds for over 30 years so my viewpoint has some experience :slight_smile: So just because you are using a “digital” signal, USB, cat5 data streaming, does not mean the signal will arrive perfectly. Although some connections are more viable, stable, than others. So when you use BLE it works flawlessly … I would start swapping USB devices, connectors etc … try and completely new physical path and then work backwards to find the issue. Normally when you have files, media, with gaps always at the same point it means that the file is being “clipped” so at a certain point your are dropping from 192 to 96, or 24 to 16, etc … something is down sampling your files. So this would indicate a potential software issue, driver maybe, but as above I would try to find a new hardware path and see whether the problem reproduces. Good luck.

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Excellent troubleshooting;
looks to be an issue with the data loading…
different drives have memory chips of varying sizes, and depending on the memory buffer of the equipment interfacing with it might make a difference.

(that is my primary takeaway based on the testing already done… although typically when reading such a heading one would assume ‘two second gaps’ have been introduced in the recording stage- this DOESN’T seem to be that)

The fact it works via bluetooth is due to the way it will stream the information in a way that loads the buffer continually with about the same amount of information…

Some high resolution tracks probably run over several chips in their storage location and due to the way the drive is interfaced with, might lead to a buffer underrun… where it has run out of stored data, and like a CD attempting to track a new location, for example, when in ‘random play mode’; the time it takes to find the next bit of data in the chain takes longer than the time the requesting device needs’ to actually get it.

Seems like the Denon simply uses more RAM to keep ‘more in its buffer’.
No doubt a firmware update might be able to fix this… (but not necessarily ideal); I’d move the files onto a different thumbdrive… perhaps try a small thumb drive; say 8GB and a larger one, say 32GB…- I’d keep to those sizes (or less) whilst troubleshooting as that removes a factor from the equation (32bit address spacing/‘file system limitations’).
whilst I feel I am talking out my rear with this post… Truth is I am just taking a punt as it might help another community member pick up the torch and run with it.

But, yes,… try moving the same files onto ‘yet another’ storage device, and see how the player handles them from there.
(And of course report findings here for us to interpret further)


Thank you very much for your reactions!

As I indicated, I used USB keys of as few as 16GB – I also suspected that it may have to do with the device’s own interface or with a driver incompatibility. However, in view of the fact that with all external devices the behaviour is the same, combined with those devices being happily read by both the Denon and the laptop, I think that it has to do with the way the Naim is reading the USB devices. I tend to agree with whitedragem that this is due to buffering, it may just happen that specific data streams cause some overflows or something that triggers a gap in the DAC – by the way, “gapless play” works well, I have tested this already. Again, it is just with specific pieces (right in the middle of the track!), from specific albums, whereas the vast majority of the albums are properly read (and, I must admit, the sound quality is absolutely stunning!). As concerns Filippe’s reaction, I tried USB and Bluetooth, but with this I kind of run out of options, since I do not have a music server.

It may be so that I have to settle down to listening the “faulty” albums on the Denon. But my remark can be a heads-up for the Naim specialists to look into the matter for future updates.

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Maybe try formatting the thumb drives with different block sizes as that may affect the access time.

Also, try copying just the affected tracks to the start of a cleanly formatted thumb drive.

Problem with applying two solutions in ONE go is that we don’t know which worked… but, if you find a success, a lil more trial and error should have it sorted, yes?

I’d try the smallest block size and the largerst block size allowable by your formatting tool as two examples that might offer a variation in performance.
Also Fat32 vs ExFat.

Great way to waste a day?!
Please report ANY things tested as it is nice to have a historical record (others may wish to know).
Cheer/ “Thanks in advance”

@IoanLager have you tried playing the flac files from a UPnP server like Asset on your network? If they play fine like that you’ll know for sure that USB is what is causing the problem.

@elverdiblanco: I do not have that server. @whitedragem: I shall try those options, but that will have to wait until the weekend. If I learn something, I shall definitely let you know.

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If you have a Windows computer or a Mac you can get a free 30 day trial of Asset and put a selection of your flac files on the same machine. That would at least tell you where the problem is if they play back OK via UPnP

This might be a long shot, but what size is the artwork? I’ve had playing problems with large artwork, and now I keep it to a Maximum of 1000x1000.

Dear friends,

Apologies for the latency!

@GadgetMan: Thank you for the suggestion! I checked the resolution, it is 700x700 → I have serious doubts that this should be the cause.

@elverdiblanco: Thank you for the suggestion! I may check it, although the fact that the issue does not turn up when using Bluetooth streaming is pretty conclusive for the glitch being in reading from the USB port.

@whitedragem: I did not yet time to do the tests → I shall inform you as soon as it happens.

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If you try a UPnP server like Asset you may well stick with it. If nothing else it would save you from having to constantly unplug a SSD drive from the Atom any time you want to add files to it, and by all accounts it is more fully featured than the UPnP server built in to the Atom

Dear elverdiblanco, this sounds really enticing, I shall consider this option in the future.

Asset is a one-off payment of around £30 and for me and plenty of others on this forum worth every penny

There may be a SQ difference between UPnP and the USB-stick.

There is such difference on my ND5 XS2, with ripped and downloaded files on the (hi-quality fast read/write) USB stick music is crisper. It is softened somewhat playing these same files via UPnP, like it does with Qobuz streams. All via Wifi, might be different via wired.

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That’s an interesting distinction, that I hadn’t considered. Sure, saw the antenna in the ND5 XS2 box. But it was never used, as we are fortunate to have structured cabling through out our home. Connected to super super fast broadband too.

( Little secret :wink: spent some years working with networks and so have a bias for always, where ever possible, using the best cable wired system you can muster, in a building).

Now that I think about it, suspect the presentation might be a little different, even maybe subtlety different. So, might explore that idea sometime. Maybe over the Christina’s holidays with a spare afternoon.

Good thinking @daddycool


Being active in several ICT domains and generally being somewhat nerdy I share that bias :wink:

At home I have to be very pragmatic though. Some life circumstances taking up a lot of my time and energy. No option to do construction in the apartment, and understandably no blessing from my better half to run loads of network cables visibly through the rooms!

I pondered unsuccessfully on available options other than the 3-node mesh network distributing 1Gbit cable internet, which to be honest works flawlessly throughout.
I didn’t see an advantage in connecting the streamer via a cable to one of the wireless nodes so rely on the ND5 XS2’s own antennae. Strong reception, no drops, all good.

(I managed to use the one available blank pipe and spare electric group for a dedicated decent earthed mains with quality components for the system, that was the max)

Would be nice to hear from others who have been able to do the comparison wifi vs wired. I haven’t read much about that so far. So if indeed you have some spare time over Christmas it would contribute to the knowledge base! But possibly a wired network may be new choices (cables, switches) best left unavailable to me for my peace of mind.

Apologies for having hijacked this thread, we could continue this under the Innous Zen thread.

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My ND5 XS2 has only ever been connected by WiFi and using UPnP. Playing from a USB stick will be an interesting experiment.

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Sorry for this retarded reaction. It is good that daddycool brought in these points. Strangely, although my work is in the development of wireless links, I will never replace a cable (wired or glass fiber) by a wireless connection unless otherwise not possible :wink:

Having said that, a little anecdote: My wife and I were looking for fixing the obvious limitations of the DAC in our Denon and, at some point, we went to a very nice hifi studio for testing, among others, an ND5 XS2. I had a USB with a couple of favourite test tracks. We tested two streamers (we have also tested others before) and after plugging in the USB in the ND5 XS2 we instantly knew that if we shall ever acquire a streamer, it will be a Naim. But then I asked the shop assistant to turn on Qobuz (high-resolution, wired connection) and played one or two of the same tracks. And both my wife and I decided on the spot that neither Qobuz, nor any other streaming service, will be on our shopping list in a foreseeable future. The reason was exactly what daddycool mentioned, the sound lacked completely and utterly the crispness of what we knew from our downloaded music. The high-resolution Qobuz sounded on the ND5 XS2 worse (flatter, less distinct, less depth) than the USB-saved files on our Denon. And this is no accident, it is about the manner in which streaming protocols work. And the same goes with a wireless connection in house: no wireless protocol can outperform a properly buffered USB transfer, it is inherent to the transmission-line based EM propagation.

Coming back to my original promise to whitedragem, I hope that I shall have the time during the Christmas holiday to play with various USB-key file formats.

Wishing you all a happy festive time!