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LambMN
2007-04-07, 17:17
I have a Squeezebox 3 and I am trying to run the digital coax output into an external DAC. I do this and the DAC only detects a 32khz sample rate, not a 44.1khz sample rate as I would expect. I know the DAC does 44.1, as when I hook up a CD player that works fine. It is an older DAC, but I would expect it still to work on 44.1 with the SB. Anyone have any experience with anything like this?

Thanks.

Balthazar_B
2007-04-07, 19:20
Which DAC are you using?

LambMN
2007-04-07, 19:36
It is a Anodyne Adapt DAC.

seanadams
2007-04-07, 22:32
There is no way that the DAC is actually running at 32KHz. The question is why is it _displaying_ that sample rate. I don't know... I am sure that we report our sample rate correctly.

LambMN
2007-04-08, 11:17
I do not know a whole lot about DACs, do you have a suggestion for how I can track down the issue? Thanks for the response.

Eric Seaberg
2007-04-08, 11:59
How did you rip your files? I have 2-SB3s and a Transporter and have never seen this... I only use the digital outs. However, if your files are at a sampling rate of 32kHz, then the digital out will match, just as playing back a 48kHz file spits out a 48kHz sampling rate from the SB3. Same thing with 96kHz, etc.

LambMN
2007-04-08, 12:23
I have ripped them to apple lossless using iTunes. I assumed that the sample rate was 44.1. I will try ripping a CD with 44.1 wav and see what that gives me.

Eric Seaberg
2007-04-08, 15:27
It will be 44.1kHz. You'd have to really go out of your way to change the sample rate, and most programs can't do that. I have very expensive software to do that going back and forth from 44.1 to 48 for TV post-production. Just had to ask...

Have you tried listening to the analog out of the SB3 to make sure it SOUNDS RIGHT? Many times we forget to use our 'ears' to tell us if something's right or not. ;-)

seanadams
2007-04-08, 15:44
What I meant to say is that there is no way that the SB3 is sending a 32KHz signal. It is not capable of doing so. So it is not a problem with how you've ripped your file, it is a problem with how the DAC is _displaying_ the sample rate that it _thinks_ it is receiving over the s/pdif. It is almost certainly a problem in the DAC, not the Squeezebox, but why the DAC behaves differently with a CD player I don't know. It is probably misinterpreting some of the out-of-band data in the s/pdif signal. One possibility that just occurred to me is that it could be misinterpreting the 24-bit signal from SB3, since a CD player will output only 16 bits. Try setting SB3 to 100% volume and playing a 16-bit FLAC, WAV, or AIFF track (NOT an MP3), and then resetting the DAC.

Also do you have any technical info about the DAC? Google turned up very little.

tomjtx
2007-04-08, 16:17
You gotta love it.
The head honcho was googling the OP's DAC to answer his question on EASTER SUNDAY!

And we were worried the Logitech deal might destroy the Slim culture?

LambMN
2007-04-08, 19:02
I tried playing a 16bit 44.1khz wav file and reset the DAC and it still locked on 32khz. The lock seems to get set when the connection is made when the DAC is turned on, and does not change with different file types.

It does sound good. I have not heard a lot of music sampled at 32khz but it does not sound worse than with just the DAC on the SB3.

I do not have more technical information on the DAC, I picked it up second hand and have not had luck figuring out much about it.

Anyone have any other ideas?

And I do want to thank seanadams and say it is pretty awesome to get such good support. It really sets SlimDevices appart.

Thanks.

seanadams
2007-04-09, 06:34
It does sound good. I have not heard a lot of music sampled at 32khz but it does not sound worse than with just the DAC on the SB3.

It's not playing at 32KHz! I assure you it is actually running at 44.1, but displaying the wrong frequency for some reason.

Skunk
2007-04-09, 06:47
Anyone have any other ideas?


Did you try setting volume to 100/100 like Sean mentioned?

You might also try 'Digital Output Level Is Fixed' in Player Settings|Audio, and turning Replay Gain off, but I could be wrong.

LambMN
2007-04-09, 08:05
I am sorry for the confusion Sean, I believe that it is running at 44.1. I was just saying that not having heard anything sampled at 32khz I would not know for sure what it sounded like if it was. But it sounds good, so I believe it is not running at 32, just not being displayed correctly. Thanks again.

I did set the volume level to 100/100 and I set the digital output to fixed. I have not tried turning Replay Gain off but I will give that a shot and see what happens.

Thanks all.

LambMN
2007-04-11, 08:07
Well, I set the Replay gain to off, I also verified the SB thinks it is playing a 44.1khz file, and I also reset the Xilinx clock chip as instructed by SlimDevices tech support. I also ripped a file at 48khz and played that, all with the same result. I am convinced that the issue is with the DAC and it is not displaying properly, I just wish I could figure out why.

Thanks again to everyone for their help, and especially the SlimDevices crew.

Skunk
2007-04-11, 08:33
I also verified the SB thinks it is playing a 44.1khz file...I am convinced that the issue is with the DAC and it is not displaying properly,

Wouldn't that suggest the problem is with the squeezebox (considering also that your cd player displays properly)?

As we saw in the emphasis thread, Squeezebox doesn't follow the redbook spec to the letter.

seanadams
2007-04-11, 09:32
Wouldn't that suggest the problem is with the squeezebox (considering also that your cd player displays properly)?

It is possible but extremely unlikely. There are no known issues with our s/pdif output, and the implementation is now very widely deployed and tested with all kinds of receivers and DACs.

This sounds like a specialty one-off product, which may even predate the common availability of 24-bit s/pdif devices. So I think it is in fact very likely that the DAC is misinterpreting some of the ancillary s/pdif data.


As we saw in the emphasis thread, Squeezebox doesn't follow the redbook spec to the letter.

Last I checked we were not a CD player, so no, we don't follow the red book spec at all!

seanadams
2007-04-11, 10:55
Here I collected the data using an s/pdif analyzer so you can see all the differences in the "out of band" s/pdif information between an SB3 and a typical CD player:

http://www.seanadams.com/sb3_cd_spdif_comparison/

As you can see, the SB3 reports its sample rate correctly, the same as a CD player. However there are many other channel status bits which are set differently, such as our clock precision, category code, and copyright bit. The CD player also transmits subcode information (track number / position) whereas squeezebox does not.

The s/pdif spec is extremely complicated so it is quite likely that the DAC is misinterpreting one of the fields, especially if it is an older or home-brew design.

Skunk
2007-04-11, 11:51
Last I checked we were not a CD player, so no, we don't follow the red book spec at all!

Something seemed dead wrong with that when I read it after posting.

Thanks for clearing it up for me :-)

Thanks for the interesting test as well.

seanadams
2007-04-11, 12:28
:) About the emphasis flag and red book... we could send it on the s/pdif and we could even apply the deemphasis curve in both SB3 and Transporter's DACs. The problem is that it is not preserved in the ripping process, so SB3 doesn't know when it's playing a PCM track whether it needs to set the bit or not.

Harry G
2007-04-12, 05:39
Since its older, it may be trying to see signals it can't otherwise identify as CD as 32k because its looking for this frequency for Japanese digital radio. I believe this is now an obsolete standard.

What about 48k? Can you rip some PCM from a DVD to try?

Fifer
2007-04-12, 06:15
You gotta love it.
The head honcho was googling the OP's DAC to answer his question on EASTER SUNDAY!

And we were worried the Logitech deal might destroy the Slim culture?

Yes, but when they were SD, the OP would have got a chocolate egg too. ;)

Eric Seaberg
2007-04-12, 07:40
Sean, is it possible that the FS bit is being output incorrectly on his unit? I've seen instances where the digital source IS putting out 44.1kHz and plays properly, but status bits 4.0-3 are set incorectly and showing 32k in the stream. Yes this usually follows the stream from the ripped data, but could something be funny with his SB3 that's changing that data bit?

Sorry I don't have the S/PDIF specs in front of me, but do remember the correct bit for AES Consumer format, and I think S/PDIF is pretty close except for level differences.

seanadams
2007-04-12, 07:57
Sean, is it possible that the FS bit is being output incorrectly on his unit?

I doubt it. This is implemented in software and there is no reason to suspect that his sb3 would be behaving differently from mine. But to confirm he could load firmware 72 and run the built-in sine test so that it's exactly the same as my test.