Archimago wrote: > Download the files, have a listen, complete my survey! > > INTERNET > BLIND TEST: MQA CORE DECODING VS. STANDARD HI-RES AUDIO > (\"HTTP://ARCHIMAGO.BLOGSPOT.CA/2017/07/INTERNET-BLIND-TEST-MQA-CORE-DECODING.HTML\") > BTW: Test will close for survey entries on September 8th, 2017.
Hi Archimago! I shall certainly give your test a go. I note your insistence in your accompanying notes that the digital input to the DAC should not be "capped" at 24/96. Although I normally use a Transporter in my system, this requirement will not present a problem since I have a (or 4!) Squeezebox Touch which I can connect to my 24/192 capable external DAC via S/PDIF with an Ethernet link to my NAS running LMS version 7.7.6-113 (simply because it's the version which Synology make readily available, & I haven't yet found the need for one of Mr Herger's more recent updates). However, this did set me thinking. I know that the question of whether the Transporter could be upgraded to handle 24/192 material has been raised on this forum before, & the issue has been dismissed because its architecture & processing power will definitely not support material of higher resolution than 24/96: however, I am using my Transporter simply to supply a digital data stream to my DAC, & do not even need the Transporter's internal clock function (because I have a word clock link from my DAC) let alone its DAC & analogue stage functions. It occurs to me that this might yet be capable of changing things. I found an interesting series of postings on appropriate digital output connections by Sean Adams himself, where he was very patiently trying to explain to someone (who had a clear excess of wealth to grey matter ratio :D) that feeding the Transporter word clock input from his very expensive dCs outboard Master Clock before linking to his equally expensive dCs DAC was a BAD IDEA because of the *-increase-* in jitter that would inevitably occur: 'http://forums.slimdevices.com/showthread.php?39770-Setting-Transporter-to-Slave-for-World-Clock-Input/page3' (http://forums.slimdevices.com/showthread.php?39770-Setting-Transporter-to-Slave-for-World-Clock-Input/page5) & the independently authored digital audio theory exposition that Sean referenced to support his contention: http://www.tnt-audio.com/clinica/diginterf2_e.html. Although the latter discussion is framed in the context of using CD/SACD transports with external DACs, the same principles will clearly apply to any "2 box" source + DAC set-up. It is the approved (Sean's post #30 above) "Clock Backwards" configuration as described in the technical article which I am using. Of course, back in 2008, 24/96 itself was still considered to be "hi res", being the DVD-A standard, & I don't think that higher sampling rates were seriously envisaged back then, although all 3 of the digital connections types used on the Transporter (AES/EBU, S/PDIF & TOSLINK) will in fact support data-streams up to a maximum of 24/192. The in-built DAC (& subsequent analogue stage) of my Transporter continues to function when the external word clock is selected via LMS settings, although I do not use its output. I cannot find any LMS setting option to turn off the in-built DAC hardware if you are only using the digital outputs to feed an external DAC & this fact might present an obstacle to my idea. But bear with me... My understanding is that LMS automatically down-samples 24/192 to 24/96 (& 24/176.4 to 24/88.2) *-before-* passing the data stream onwards when its target is identified as a Transporter (as opposed to a later Squeezebox Touch which is 24/192 capable, but lacks the handy word clock in necessary to establish a low jitter connection to an external DAC). I am wondering what would happen in my specific configuration if that down-sampling were*- -**-not-* performed by LMS: after all, the data being passed on from my Transporter to my DAC is just a stream of bits, & I have to set the sampling rate to be used to convert it to an analogue signal on the DAC itself. I imagine that in the Transporter itself the conversion of 24/192 input stream would either not occur at all (with silence in the analogue stage), or that it would be done at the in-built DAC's maximum of 96kHz resulting in a reconstructed analogue signal running at half-speed. Neither of these outcomes would be of any significance to me since I'm not using the Transporter's analogue outputs at all. Nor should they trouble the Transporter's analogue stage. OTOH, if passing a native 24/192 signal to my Transporter would cause it to malfunction in any way or even cause damage, this would clearly be another BAD IDEA! Does anyone have sufficient understanding of the Transporter's circuitry to provide clarification on how it *-would-* handle a 24/192 data stream? If there would not be any hardware issues, it would seem to be a straightforward software revision for LMS to disable the automatic 24/192 & 24/176.4 down-sampling for the Transporter -*if*- the word clock input is selected in LMS settings, since that would appear to imply _exclusively_ that my type of connection to an external DAC is being used. So maybe, just maybe, the Transporter -*could*- be made to handle 24/192 signals, even if only in conjunction with a word clock out equipped external DAC, with only a small mod to LMS... If no-one knows how the Transporter would respond to a native 24/192 or 24/176.4 signal, I'll pass the idea over to Mr Herger for his consideration. Anyway, I look forward to taking part in your test, Archimago, & returning my findings together with the other information you have requested! Dave :) ------------------------------------------------------------------------ Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=107673 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
