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Practical Devices XM6: Bit-Depth and Samplerate limitations?

post #1 of 8
5/12/11 at 7:44am
Thread Starter 

I received my PD XM6 today, and I am really wondering if higher sample rates & bit-depths are possible on this device. Unlike my NuForce uDAC2, which can be set to 96 kHz 24 bit in OSX's AudioMidiSetup, the XM6 doesn't offer a higher sample rate / bit depth than 48 kHz 16 bit. I understand that this isn't a limitation by the OS, on my Win7 partition, the device shows the same limitations.

 

Needless to say, the XM6 is a well built device with excellent sound, staging and definition, and it excels the NuForce on traditional 44.1 kHz 16 bit sound material, but I also own a couple of high definition 96/24 sound files. 

 

Is there a possibility to overcome those limitations?

Would it be better to use the uDAC2 as converter for the HiDef material, choosing the XM6 only as headphone amp via the analog path (RCA to mini-jack)?

 

Best regards and lots of thanks,

 

Martin

 

 

 

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post #2 of 8
5/12/11 at 11:23am

As far as I can tell/know, the reason why the XM6 can only take 16-bit audio (via USB) is because the USB feeds into a Texas Instruments USB controller/upsampler. You'd have to somehow replace that in the XM6's process chain to make it take anything with greater bits per sample.

 

Speaking with no experience whatsoever, I think, if you have 24-bit audio, play that through a DAC that can actually handle it (e.g., the uDAC2) and chain that to the XM6's amp (assuming that the XM6's amp is superior).

 

-- Griffinhart

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post #3 of 8
5/12/11 at 12:45pm

I mentioned this earlier in the main XM6 thread.  It only does a maximum om of 16bit/48khz because of the USB receiver chip.  I emailed James before I bought it and he was completely upfront about it.

 

Signal chain is TI receiver chip > TI asynchronous sample rate converter > Wolfon DAC chip > amp section.

 

The sample rate converter seems to bump everything up to 24/192 using separate onboard clocks for purposes of jitter reduction.  James didn't tell me all this, but that's the conclusion I came to after looking at the board and reading the spec sheets for the components.

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post #4 of 8
5/12/11 at 2:28pm
Thread Starter 

Thanks for the replies,

 

most of my audio material is 44.1-16 anyway, so it ain't that bad, I was just surprised (should've read the small print).

 

Sadly, extending the dynamic resolution to 24 bit and an upsampling process to a higher sample rate won't actually the fact that the source material will always be transmitted with a max fs of 48 kHz and 16 bit, so any higher definition sound files will be *degraded* to a certain extend. The resampling process will basically interpolate additional information from those 48000 samples received, which enhances the listening experience compared to a lower sample rate, mainly because the nyquist point is higher which is results in a less aggressive low-cut slope for the aliasing filter. Thus, most CD-like material will sound more natural.

 

In a whole, the sound of the XM6 is terrific, so I can't complain.

 

Regards

 

 

 

 

 

 

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post #5 of 8
5/12/11 at 3:25pm

     Quote:

Originally Posted by vandaven View Post

Thanks for the replies,

 

most of my audio material is 44.1-16 anyway, so it ain't that bad, I was just surprised (should've read the small print).

 

Sadly, extending the dynamic resolution to 24 bit and an upsampling process to a higher sample rate won't actually the fact that the source material will always be transmitted with a max fs of 48 kHz and 16 bit, so any higher definition sound files will be *degraded* to a certain extend. The resampling process will basically interpolate additional information from those 48000 samples received, which enhances the listening experience compared to a lower sample rate, mainly because the nyquist point is higher which is results in a less aggressive low-cut slope for the aliasing filter. Thus, most CD-like material will sound more natural.

 

In a whole, the sound of the XM6 is terrific, so I can't complain.

 

Regards

 

 

 

 

 

 

When I agreed to do the initial review of the XM6, James asked what I might suggest as improvements.  I suggested a coax or optical input as well as usb.  That should be able to bypass the limitations of a usb input.  The iBasso D-10/12 features multiple inputs, hopefully the XM7 (when James develops it) will too.

 

Cheers! beerchug.gif

-HK sends
 

 

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post #6 of 8
5/12/11 at 4:27pm

It'd be awesome if there was a way to finagle multiple inputs using the auxiliary connector...

 

-- Griffinhart

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post #7 of 8
5/12/11 at 5:39pm

I agree completely, but the aux connector is wired for control of the shuttle ("joystick") and signal lines out at the moment.  Maybe James can work something...

 

XM6 Aux Pin-Out.jpg

Cheers!beerchug.gif

-HK sends


Edited by HK_sends - 5/12/11 at 5:41pm
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post #8 of 8
6/21/11 at 12:36am

@vandavan: any chance u can comment on whether the DAC section is compatible with integer mode used in Pure Music/Audirvana/BetterSound? cheers

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