WAV vs. FLAC transcoded to WAV - Network Trace

Posted by: DaveBk on 18 October 2012

One of the perennial debates often encountered here is whether WAV sounds better than FLAC on Naim streamers. The general consensus seems to be that any perceived differences are explained by the extra processing required to decode FLAC, and the resulting increase in digital noise which could be picked up by sensitive analogue components nearby.

 
A more contentious subset of this debate is whether FLAC transcoded on the fly to WAV on the uPnP server sounds different...?
 
Personally I can't tell them apart, but I was interested in whether there was any difference in the network traffic in these two scenarios so decided to do a little test.
 
I use a Shuttle bare bone PC, with an i5 processor and 4Gb RAM running Windows 7 and Asset as the Server.  This is connected via a Netgear GS116 switch to my NDS all using CAT6 cables. They are about 15m apart with 3 solid brick walls in between. The music files are on a QNAP 459 Pro NAS next to the server.
 
I picked relatively short 2 minute track, Intro off the XX album, and converted this from FLAC to WAV using dBpoweramp music converter. I put this and the original FLAC file into a new directory and edited the metadata to change the artist field to 'Test Material' so I could distinguish them from the original album. I forced a rescan on Asset, then checked I could see the new tracks on nStream. All as expected so far.
 
For the network capture I used WireShark running on the server and captured all the packets flowing between the server and the NDS while the 2 tracks were played.
 
For the sake of simplicity I ignored all the uPnP discovery, and the content look-up between nServe and the Server and only considered the actual delivery of the music stream. It starts with an HTTP Get from the NDS, specifying the uPnP URL of the required music file. For the FLAC file transcoded to WAV the URL format is a path with forced.wav at the end, for the native WAV the path ends with a unique file ID, also of type .wav. The URL path is not the path to the file on the NAS, it is a uPnP 'shorthand' using alphanumeric tokens to represent the required file.
 
The response from the server is an HTTP 206, followed by the required file which is streamed back to the NDS. I looked closely at the WAV headers and they are different, but closer inspection showed that this was due to the meta data tags being included in the direct WAV, but not on the transcoded WAV. The data chunk looks identical - exactly the same length, and at various offsets containing exactly the same bytes. I have not done an exhaustive comparison yet, but a close 'eyeball' inspection over 30 mins could not see any difference.
 
Looking at the network exchange it is almost identical as well - 
 
On the initial handshake the Max Segment Size is set to 1460 ( no jumbo frames ). The initial receive window from the NDS is 8192, which reduces to 6732 after 3 segments have been exchanged then remains constant. It's just textbook TCP, 1460 length segments, getting ACKed, final one has the FIN bit set. I can see absolutely no material differences, other than the presumably redundant transfer of a bunch of metadata at the end of the 'real' WAV which I guess the NDS just discards.
 
So, no further forward in working out why some people hear a difference....
Posted on: 23 October 2012 by rich46

the dac runs on two psu now,cant see that a new dac will come. naim want more new customers and they dont want a box count .  unitytype products  sell the  most according to dealers. maybe a top end new preamp with dac/streamer present

Posted on: 23 October 2012 by Simon-in-Suffolk

Rich - yes I meant external PSUs. To be honest I find the current split NDAC powersupplies one of its major benefits at its price point and i am sure it is that that really helps with SQ of that device.

I agree on box count - but there appear a lot of customers who stream from their computers/alternate system, and the DAC is a natural choice for them - as well as those wanting to upgrade their current dac performance. We shall see - I suspect when the 555ND is developed there will be some trickledown into the DAC2 perhaps - or it could be to get optimum SQ for the 555ND that it has seperate streamer and DAC - again we shall see.

Posted on: 23 October 2012 by rich46

maybe.  i think naim will slow down they have put a rush of units out in he last year.

 

ps  i too run cyrus power amps mono 300s they sit on first shelf so i dont look at the front grill but the are clean and fast and do their job

Posted on: 23 October 2012 by DaveBk

Don't tempt me with an ND555, I'm only just coming to terms with the NDS...! What more can Naim do? It has suspended mass loaded PCBs, separate screened 'quiet rooms' to keep the digital hash away from the analogue stuff, dual 555PS's... All it needs is the brushed anodised sleeve and its a 500 series already... 

Posted on: 23 October 2012 by Simon-in-Suffolk

Hi Dave... Yes it is a thought but sonically you can hear that there is a space for the ND555 to go. The dynamics and organic emotion of the NDX/DAC/555PS combined with smoothness of the NDS/555PS. 

Simon

Posted on: 25 October 2012 by AMA
Originally Posted by Simon-in-Suffolk:

Guy, not that I know anything, but I wonder if a DAC2 might appear next spring. It might have suspension and two power circuits to be fed by a 555PS... We shall see. It might contain innovation that might be trickled into the potential reference ND555.

It's obviously doable but I don't think it will get a commercial success. What I do believe in is that Naim can release ND555 with SPDIF input and enable operating it as a DAC for people who are insanely in love with their CD-transports. In this case the streaming section will be unused.

 

You can bypass the Naim's circuitry but you can not bypass Naim's bank account 

Posted on: 25 October 2012 by AMA
Originally Posted by DaveBk:

What more can Naim do?

One small thing -- try to beat Linn KDS at last 

Posted on: 26 October 2012 by Simon-in-Suffolk

Hi AMA, I might be missing your point.. The current ND players have SPDIF input to use as DAC only.. So other than reniement etc there would be nothing new in terms of that with ND555.. Or more likely I've missed your point...

 

And .. I hope Naim don't end up sounding like a KDS.. That would' be disastrous IMHO, but.... I feel the NDS is slightly Linn like in presentation, so you might be on to something 

Posted on: 26 October 2012 by AMA

Simon, my point is that stand-alone DAC555 will hardly be selling well. Most people consider Naim as a complete source.Those who want to get Naim sound with top-notch DAC should go and buy more expensive NDS or ND555 and use S/PDIF input -- obviously bypassing a streaming part.

 

As for ND555 I'm sure Naim will come up with something VERY special.

Naim is too ambitious to leave the things the way they are now.

And more importantly they have a technology ground for this -- take a hint that some people still prefer CD555 over NDS 

 

But so far it seems that KDS is still the king of a streaming world.

 

btw are you sure you have auditioned KDS/1 in direct test against some Naim player? 

Posted on: 26 October 2012 by DaveBk

AMA, I prefer Naim's voicing over Linn's, so I cannot agree that the KDS is king. At this level I find it difficult to compare absolutes as the interaction between room, speakers, amp and source needs to be considered. I'm very pleased with what the NDS does in my system, my room and my ears. Simon finds it a bit too smooth, and lacking in dynamics in his...

 

It's great to see other people's views and experience, but single dimensional ranking of x is better than y is far too simple.

 

If Naim ever bring out a ND555 then I'll be queuing up for a demo. I suspect a 552 will come before this though 

Posted on: 26 October 2012 by AMA
Originally Posted by DaveBk:

AMA, I prefer Naim's voicing over Linn's, so I cannot agree that the KDS is king. At this level I find it difficult to compare absolutes as the interaction between room, speakers, amp and source needs to be considered. I'm very pleased with what the NDS does in my system, my room and my ears. Simon finds it a bit too smooth, and lacking in dynamics in his...

 

It's great to see other people's views and experience, but single dimensional ranking of x is better than y is far too simple.

 

If Naim ever bring out a ND555 then I'll be queuing up for a demo. I suspect a 552 will come before this though 

Dave, 552 makes by far the greater change in sound comparing to NDS vs nDAC vs KDS.

 

As for the voicing: KDS/1 sounds nothing like traditional Linn players. It's very open, transparent, very dynamic, it features razor-sharp transients and weighty bass.

 

I have a strong preference of Naim sonic signature and the fact that I'm using KDS merely means that Linn somehow managed to make a very Naimish-sounding player. I don't advertise KDS on this forum -- but I do push Naim towards the main virtue of the Linn's flagship: the incredible analogousness which only few digital sources could match. It takes me so much closer to LP12 than any other digital player ...

Posted on: 26 October 2012 by DaveBk

I've only heard the KDS at a show once AMA, so I'm not that familiar to be honest. Perhaps I've been all digital for too long to tell the difference....

 

I'll just have to make do with the NDS for now