REW Measurement Artefact or miniDSP SHD Studio / Volumio Bug

mrlawng95

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Hi.

Based on my measurements with REW and a UMIK-1, I have either encountered a measurement anomaly with REW or my SHD Studio or Volumio is altering the integrity of all files rendered via Volumio. This was validated by measuring signals passing through separate paths on the SHD and viewing drastically different IR and step responses of my speakers. Please refer to the attached images.

First some information on the issue as it's not happening on all inputs:

My SHD Studio is connected to my Naim NAC 272 DAC / Preamp via coaxial SPDIF.

I have a Wi-DG in repeater mode connected to the SHD Studio via LAN cable. I have enabled Roon via Volumio and now can use the SHD Studio as a Roon Endpoint.

I also have a chromecast built into my Sony TV which also acts as a Roon endpoint. The TV is connected to the SHD Studio via Toslink.

I have used the exact same sweep (48 kHz) with timing reference generated by REW and imported it onto my server and to a USB stick. I have used the same file, mic, measurement system, speakers, and all other conditions are the same and these results are consistently repeatable. The attached measurements were made with Dirac On but the issue is the same if I turn it off. I've also validated this on both windows and MAC versions of REW.

Signals fed through Roon>Chromecast>SHD Studio>Naim NAC 272 are hitting my DAC with full integrity of the file as you can see in the attached images. Signals fed through Roon>Volumio SHD Studio > Naim NAC 272 are not. I have disabled all Volumio processing as well as in Roon. Interestingly, a USB stick with the same exact REW Sweep, managed by Volumio, also exhibits the same exact behavior as Roon via Volumio which leads me to believe this is an issue with Volumio or its implementation on SHD Studio.

I have an SHD Studio and have downloaded all recent updates including the version of Dirac released 11/13.

Obviously this is disappointing! These issues have an audible impact on critical listening.

Several knowledgeable people on another forum suggest this could be a REW artefact. My knee jerk reaction was that this is wildly implausible. Especially considering that Roon>Chromecast path measures correctly.

I'd be appreciative if @JohnM or someone else could chime in here and either confirm it's not REW or provide a high-level summary of how a measurement artefact like this can happen on one input and not another with everything else being equal.

Thanks!
 

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John Mulcahy

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Apr 3, 2017
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Looks like a major clock rate mismatch to me,. Something in the system is operating at a different sample rate, e.g. 44.1k vs 48k.
 

mrlawng95

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Appreciate the quick reply John. I will post any updates from miniDSP as I continue to work this through with them.
 
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