Sound drops / cuts Pi3 and Hifiberry Digi+

patb

Hello,

I am experiencing occasional signal drops. The sounds stops for a second and comes back on again. I have the digi+ connected to a Naim Ndac via coaxial cable but also tested it with optical and coaxial cables, different input sockets, different PSUs etc. and the signal keeps dropping regardless of these changes. No signal drop occurs with other signal sources (a TV via optical for instance) or if I am using a direct USB input on the DAC.

I might add that I feed data from an external HDD connected through Pi3's USB inputs. I have tried mounting the HDD using the router and feeding data over LAN rather than directly through USB and I still experience the same issue. I have now also tried a PC folder share and I get the same drop of signal after a couple of minutes. I have tested WAV, FLACs, MP3s - all cause the same issue.

The only time the sync light light remains on with no signal drops (please read below) is when I play 24bit source material. Naim NDAC has a sync indicator on the front panel which (as per the manual): "The sync indicator illuminates to indicate that the DAC’s internal clock is precisely synchronised with the input data stream. The DAC will continue to operate if synchronisation is lost but its audio performance may be compromised. Synchronisation loss is generally caused by an out-of specification clock in the source component." I was also told by Naim that when the sync light switches off, it indicates that at some point the connection was lost i.e. a drop in feeding the data has occurred and caused a temporary loss of music.

I hope that all the extra information is going to be helpful in troubleshooting the issue.

I am running Linux version 4.4.11-1-ARCH (builduser@leming) (gcc version 6.1.1 20160501 (GCC) ) #1 SMP Thu May 19 18:46:14 MDT 2016

Many thanks!

Pat

PeteB

Hi Pat,

And welcome to the forum!

patb wrote....
I am running Linux version 4.4.11-1-ARCH (builduser@leming) (gcc version 6.1.1 20160501 (GCC) ) #1 SMP Thu May 19 18:46:14 MDT 2016

What RuneAudio revision or version number does this correspond to? Are you running the latest RuneAudio image from the download page, or is this on some other platform?

patb

Hi Pete,

The image I am using is RuneAudio_rpi2_rp3_0.4-beta_20160321_2GB.img
I did a manual update as suggested in this thread: #3570 as I had experienced the random channel swapping issue. The channel swapping has been fixed but I am now experiencing the loss of sound.

PeteB

patb wroteHi Pete,

The image I am using is RuneAudio_rpi2_rp3_0.4-beta_20160321_2GB.img
I did a manual update....

Ok, that makes sense, I have a Pi2 so I have the older version.

The Digi+ has a single crystal, and derives 44.1K and 48K from that one crystal. From the HiFiBerry forum:

...The 44.1kHz frequencies are off by about 150ppm from the "correct" frequencies. The 48/96/192kHz are "better" in a way that they are less of from the "correct" frequencies

So if you are seeing a problem only at sample frequencies which are a multiple of 44.1, this might be the reason. However if the drops happen with higher bit rate, higher def files, then the reason would be something else.

If you have sound drops that last as long as a second, that would be a very long time in terms of signal data loss. (Mine last much less than a second, more like a quiet pop which is less loud than the avg music volume.)

Have you tried increasing the buffer size, in case it has something to do with reading the data from the source via USB or LAN, rather than with the sync of the output?

patb

Perhaps it is less than a second, it's a drop then the music comes back on. No pops though.

I'll try to increase the buffer, although, this would be more about throughput issues, like you say. 24bit files are even larger and cause no such issues.

PeteB

patb wrote...24bit files are even larger and cause no such issues.

Yes, I agree, but it was a simple suggestion...

Most of my 24-bit files are 96K/24-bit or 192K/24-bit. The sample frequency is a multiple of 48KHz. These sample rates are closer to correct (according to HiFiBerry Team).

Something else I would look into is what is actually being sent to the Naim DAC? Is MPD resampling the files for some reason, because the handshake is not working (does the Naim give you a display of the sample rate and bit depth while playing, and does it correspond to the file)?

patb

Hey,

I welcome all suggestions. I also tried increasing the buffer just in case with no improvement, unfortunately. Your input and the quote from Hifiberry forum re the single crystal and its native frequency is something that finally makes more sense. I've found no leads despite searching across different forums. Interestingly enough, I found a similar post here:

https://support.hifiberry.com/hc/en-us/community/posts/201492802-Limited-sync?page=1#community_comment_207293165

NDac does not display the sample rate, the only indicator is the "all meaning" sync led light

Is there any way to make sure that MPD does not resample the files? Check in the Debug info?

Your input is much appreciated!

PeteB

You can see what is being sent to your Naim DAC, but only while the file is playing, by looking at the contents of a file, which can be found using the card# of the dac. The card# is part of the path to the file.

I am sort-of paraphrasing some of Frank's posts here:

Examples:

cat /proc/asound/card1/pcm0p/sub0/hw_params

cat /proc/asound/card0/pcm0p/sub0/hw_params

There will be two or three similar files, but only one card# corresponds to your USB dac. You can find the card number by listing the devices:

aplay -l

the content of the file will look something like this:

# cat /proc/asound/card1/pcm0p/sub0/hw_params

access: RW_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 44100 (44100/1)
period_size: 5513
buffer_size: 22050

PeteB

You could also look at what the Naim DAC lists as compatible formats, just in case there is something to be learned from that. Here is a link to a utility that can be used to do that:

https://lacocina.nl/detect-alsa-output-capabilities

Pete

patb

I will test the Hifiberry with a friend's Pi2B first as his setup is identical (apart from Pi3B) and he experiences no such issues.

On replicating the issue, I have monitored and timed the drops and they seem to happen at around 6mins and 15secs of playing time.