NDX Streaming 24-bit/96 kHz
Posted by: naimUnT on 17 October 2011
My NDX has the original 24-bit/96 kHz capability but when I stream iRadio and UPnP (FLAC or WAV files ripped from CDs using dbpoweramp) into my Accuphase DAC (DAC-30 with 192 kHZ capable) the signal seems 'lost' every time I switch from FM radio to iRadio or UPnP. My NDX digital out is usually set to 'Native' which causes this phenomena of 'locking'. I have to cycle the Accuphase DAC to another source and back again before it locks. But, strangely, when I set the NDX to '24/96' all is well and the signal locks firmly on my Accuphase DAC regardless of the NDX source playing. I find this very annoying and wonder what might be the reason! Could the more informed please enlighten (educate) me?
Posted on: 17 October 2011 by Simon-in-Suffolk
Hi, when the NDX is on native, the SPDIF changes bit depth and sample frequency when changing source. This means the header bits on the SPDIF stream change to reflect the source. It seems your downstream DAC is not resyncing the bit stream and then correctly decoding the SPDIF headers mid stream. This may because of timing or other reasons of the interruption to the SPDIF sources when switching.
When the NDX is set at 24/96 then the SPDIF stream remains at constant settings irrespective of digital bit depth or sample rate of the source, as the NDX modifies all sources to 24/96.
However my view the down stream DAC should re sync and adjust to the new SPDIF parameters, as that is a valid thing to do.
Simon
Posted on: 19 October 2011 by naimUnT
Thanks for your insights, Simon! From your reply it would suggest that my non-Naim DAC is not doing what a DAC should be doing! I read the Naim White Paper on the NDX and wonder if it could be Naim's Own algorithm implementation. I don't know enough about the technical aspects of offer any explanation other than to report what I am experiencing and to make some observations as I see it. I tried my Benchmark DAC with another NDX unit and I experienced the same phenomena as my own NDX, suggesting that it's nor a lemon NDX.
Posted on: 20 October 2011 by Simon-in-Suffolk
Hi, it is possible there is some sort of interoperability between the NDX and the Accuphase DAC. I am not really sure what the NDX would to the PCM stream when it is turning back into an SPDIF bit stream, as when set to native it only appears the NDX is reclocking the source and converting to PCM if another codec is used. The DSP oversampling and filtering only kicks in in the NDX if using nits internal DAC.
Does your Accuphase correctly re sync if you play a hidef upnp file followed by 16/44.1 one?
Simon
Posted on: 20 October 2011 by naimUnT
So if I am routing the NDX's digital out, the signals will not be upsampled but will be as it is received. Excuse my ignorance but how do I tell whether a file is high resolution or not? What do I look out for?
I have been listening to the NDX via it's analog out and must say that it sounds very good in my system. I understand that many have taken the NDX to higher levels with separate PSUs and the inimitable nDac. To truly appreciate the NDX at the higher level, I believe one's equipment must be similarly at a higher level in order to hear and appreciate the improvement. With a integrated or even 200/202 (with HC2 & NPSC) I think the NDX as-is is already very, very good!
Posted on: 20 October 2011 by Simon-in-Suffolk
Correct, if you set the ndx to native, and use the digital out there is no up sampling. The NDX is very good standalone when using its own DAC and DSP. In this mode ithe NDX internally upsamples and applies the transfer function filter using 32 bit precision in the DSP and uses an internal i2s interface between the DSP and the DAC with the internal DAC chipset DSP disabled in favour of Naim's discrete implementation.
This is the same approach with the nDAC but the latter employs a more accurate/refined conversion approach and more power supply decoupling options although the DSP implementation appears similar/identical.
What constitutes a hidef file is slightly open to interpretation, but arguably is usually referred to a non lossy file format with 24bits precision and greater than 44.1kHz sample rate. (Although HDCD is at 20bit at 44.1kHz using a companding algorithm implemented by a DSP to process a specially implemented16bit 44.1kHz PCM file. Some rippers convert HDCD to 24bit 44.1kHz PCM files.) I think i am right in saying the NDX displays these sample file parameters on the green display. Nstream shows just the codec and data rate.
Simon
Posted on: 22 October 2011 by naimUnT
Simon: I have observed that the NDX's FM tuner ouputs 48.1 while UPnP and iRadio are both at 44.1. When the NDX board is finally upgraded to 192 kHz, would this cure the phenomena I am experiencing?
It seems quite clear that the NDX has done something to the 'native' signals that causes hiccups on my Accuphase DAC whenever I switch from 44.1 to 48.1 or vice versa. Strangely, on native, if I stick to iRadio only, and switch between iRadio stations, the Accuphase DAC seems able to handle this. But, the minute I switch to FM radio (48.1), I can hear a 'tick' sound in my Accuphase DAC and no music is heard
I I have to accept 24/96 instead of 192, what is do I have to sacrifice? Most (if not all) of my listening are of CDs ripped to redbook 44.1 standard and radio is confined to FM and iRadio.
Really appreciate your advice and invaluable responses!
Posted on: 23 October 2011 by Simon-in-Suffolk
Hi, without knowing what is happening in your setup it's hard to say whether the new boards will improve thing. Instinctively they feel unconnected.
You say FM/DAB is 48.1 kHz, do you mean that or do you mean 48kHz? If it's the former it looks a non standard sample rate to me, which is perhaps why your downstream DAC can't lock.
Valid sample rates are here
http://en.wikipedia.org/wiki/Sampling_rateSimon
Posted on: 25 October 2011 by naimUnT
Hi Simon: you are right, it should be 48 and not 48.1 kHz! My bad! This is a typical sample rate which most (if not all) DACs should have no problems locking into! I have a feeling that the digital out of NDX has been 'processed' through Naim's circuitry but I don't know enough of what this might be. So, even though it is 'native' the NDX has done something to the signal.
Anyhow, I am really intrigued by all of this and hope to be able to find an explanation to this phenomena.
Btw, how much would I miss if I don't have 192 capability? Most of my listening is with ripped CDs (dppoweramp) and internet radio (and the odd Cable TV audio). Thanks for your inputs!
Posted on: 25 October 2011 by Simon-in-Suffolk
Hi, I guess only you can determine how much you will appreciate 192 as opposed to 96. It will be subtle, and it's worth bearing in mind that much professional studio audio is at 96kHz. I suspect at this sample rate the compromises in digital to analogue conversion in a particular implementation will be an important contributor to differences in sound quality as much as the higher frequencies present in the media. If I am right one might be to able to achieve a significant part of any sound quality difference by up sampling the 96 content to 192 before streaming or play back.Plenty of scope for fiddling around when my NDX is upgraded.
Simon
Posted on: 09 November 2011 by naimUnT
Thanks Simon! Yes, I guess the only way is for me to listen to a 192 rip and see if I Luke it. From what I have been listening (redbook and 24/96), I seem to prefer redbook 44.1. The 24/96 sounds like its been processed and synthesised, like going through those ghastly equalisers of yore!
With the help of the Berkeley Alpha, I have been able to determine the following in my NDX:
If NDX is set to native, FM radio streams at 32 kHz (surprisingly low) while iRadio and UPnP streams at redbook 44.1.
If I set the NDX to 24/96, FM radio, iRadio and UPnP consistently streams at 24/96 which suggest that the NDX upsamples the digital streams. I am not sure I like this sound! It has a wider soundstage and has quite a bit mire air and space but it sounds artificial to me. My NDX dies not have the new 192 boards. Does this mean all files are upsampled to 192?
Posted on: 09 November 2011 by Manu
In the ND5XS the digital out options are Native or 24\96, so I guess the NDX with new boards will be the same so not upsample to 192.
Posted on: 10 November 2011 by naimUnT
Manu: I'm sorry but I'm quite confused here! Won't the new boards display as 24/192? Otherwise, what is the improvement from 24/96?
Posted on: 10 November 2011 by aysil
I guess the new board will be able to handle incoming 24/192, but this won't mean it will upsample other formats to 24/192.
Posted on: 10 November 2011 by Manu
Posted on: 10 November 2011 by Simon-in-Suffolk
It's interesting, theoretically having a 96kHz up sampled rate *sent* to the DAC via SPDIF whose DAC is ultimately bandwidth limited to I believe 768 kHz will out perform the equivalent signal uplampled to 192 kHz sent to the DAC with the same limited bandwidth of 768 kHz.
This is why it is best to leave the NDX output to native, especially if connecting to the nDAC.
Simon
