Sample rate issues

umea101 · 3752

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Offline umea101

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on: April 06, 2015, 11:16:02 PM
Hi!

I have been playing with my new Bottlehead DAC over the weekend and encountered some issues with sample rate switching.

First I connected via USB to my cuBox running Volumio and everything worked fine.
Then I connected via TOSLINK to my DVD player and the 48 kHz sampling rate produced distorted sound.

After rebooting the DAC with TOSLINK selected it now is able to switch between 44.1 and 48 on the DVD input and this is how I am using it right now, but I would like USB to work as well.

When I have time I will do some more experiments.

Any thoughts?



Offline Grainger49

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Reply #1 on: April 07, 2015, 02:04:06 AM
This problem was written about in detail in another thread.  The answer is exactly what you found.  You have to turn off the DAC, wait one or two minutes and reboot it on the newly selected input. 

There is surely more in the other thread.  I didn't find it immediately but I'm on my first cup of coffee.



Offline umea101

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Reply #2 on: April 07, 2015, 04:02:39 AM
Just wanted to flag a slightly different issue: If I restart as describe in the other thread it still does not work. I need to restart with TSOLINK selected to get it to work. The TOSLINK works now, but I did not get the USB to work at the same time. I will need to investigate some more options, as I have not tried all possible sequences yet.



Offline Grainger49

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Reply #3 on: April 07, 2015, 05:54:35 AM
IIRC, the answer was to play something on USB that is 44.1/16 before switching to Toslink there is no problem. I've been following this closely but don't know if I will use USB when I get my DAC.



Offline fullheadofnothing

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Reply #4 on: April 07, 2015, 06:51:30 AM
It sounds like your TOSLINK issue is not the sample rate error that has been written about elsewhere (concise summary here http://bottlehead.com/smf/index.php?topic=7692.msg74134#msg74134 ), but a second problem that has also been encountered. I am guessing that the sound has some "robot chirps" over it, but plays at the correct speed and the DAC displays the correct rate. I have a sound file that I could send you if I knew who you were. This I have found will clear up if you simply let it play for 30 seconds, or reboot the DAC.

As for your USB issue, I will need more information to proceed. When you say that USB doesn't work, what does that mean? Wrong sample rate shown? Doesn't show up as a device? If it shows up as a device does it show up as an audio device (i.e. in ALSA mixer/ aplay -l)? Doesn't pass sound? Doesn't work with your preferred player (i.e. can you pass sound on a simpler player)?

Additionally, I don't know much about cuBox. I did a bit of research, and the OS seems to be based on an Ubuntu distro, but limited to a 2.6 kernel. How much audio stuff have you done with it? Have you used other DACs with this box, if so which ones?
« Last Edit: April 07, 2015, 07:05:33 AM by Doc B. »

Joshua Harris

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Offline umea101

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Reply #5 on: April 07, 2015, 09:26:00 PM
Thanks for the quick answer. Yes, the sound could be described as robot chirps. I experimented some more yesterday and did not encounter any more robot chirps. I did reproduce the other sample rate error issue. After playing 48kHz audio from the DVD player, the USB got stuck on 48kHz as well. Strangely enough, the sound was playing fine, only 10% faster, which made the Beatles sound like Huey, Dewey, and Louie.



Offline John Swenson

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Reply #6 on: April 08, 2015, 05:43:50 PM
The solution to going from S/PDIF (optical or coax) to USB, is to have the first piece of music you play on USB use the same family as the last piece played on S/PDIF.

For example if your last piece on S/PDIF was 48KHz, play something at 48, 96, 192 etc on the USB. It doesn't have to be a full song, it can be a half second of tape hiss at the right sample rate. I would just keep two files handy, one at 44.1, one at 48, that you can play before anything else. As above they can be very short and soft so you don't even notice them.

The other issue can happen if the DAC is set to USB and you have something plugged into optical or coax and actually playing, when you switch over from USB to S/PDIF (optical or coax) you can get some weird sound for a little while. This should not happen if you don't have anything playing into optical or coax while the switch is set to USB.

John S.


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Offline umea101

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Reply #7 on: April 08, 2015, 11:59:00 PM
Dear John,

Thank you for the answer. This should solve the problems. Is there any plan of a firmware update to address these issues?