pc based juke box

from what i understand the squeezebox's jitter performance is quite good at under 150psec iirc. however as some can hear differences between transports and digital interconnects there are bound to be percieved differences.
one thing i have noticed is this:
my dax 2 has 2 methods of locking on to the digital signal, one for low quality / high jitter signals and one for high quality / low jitter signals. the latter illuminating a little 'crystal lock' l.e.d. on the front of the dax.
Now with flacs the crystal lock light stays off HOWEVER with MP3's the crystal lock light comes on! so there is something going on in there somewhere and definately room for improvement with flacs. i'm going to try a jitter reducer in the near future so we'll see.as ever with hi-fi nothing is ever simple.
that said even without 'crystal locking' flacs are noticably better than mp3's - well 128mbps mp3s anyway.

one of the big 'naimisms' is the belief that putting the dac chip as close to the transport as possible is a crucial part of the naim sound so a seperate naim dac is unlikely - unfortunately.
for me though dac technology peaked in the mid 90's with the last of the proper multibit dac chips. nowadays dac's are designed to decode dvd and sacd bitrates which unfortunately means that the data stream has to be 'upsampled' or sample rate converted which to my ears does nasty things to the music. give me a good 16, 20 or 24 bit datapath, multibit converter with 8, 16 or 256 times oversampling any time. unfortunately these are either very specialist and therefore expensive (jvc k2) or new old stock (tda1541 double crown etc.) which are not replaceable if they go pop. i just pray my dax 2 lasts.
cheers


julian

 

Just to clarify, my original post is meant to address the question of whether a conventional CD player could be replaced as the source in a high end audio system by a properly set up PC based jukebox. I'm also basing my analysis on the theoretical assumption that no matter what CD player one wishes to use as the benchmark in a comparison of CD source vs. PC jukebox source, the same DAC circuit would be used in each case. I realize this theoretical DAC may not exist (ie. Naim don't make a CDS3 DAC available) but I want to keep the analysis simple and therefore let's assume the DAC does indeed exist as a separate component.

Tom, I think you understand what I'm getting at with my questions. I realize the CDP transport is real-time and therefore has a more complex task. But as far as providing the "raw data" to the DAC, it seems that part is universal no matter what the "transport" mechanism (CD, HDD, RAM, etc.). There are timing issues apparently but the raw data bits never change no matter the reading mechanism. Please correct me if I am wrong here.

As far as julian's point about the Naim philosophy of keeping the DAC physically close to the transport, I don't know all the reasons for this. However, given an ideal data stream (one that is sufficiently buffered), could a media hub and DAC combination not include some sort of clock module that times the data to the DAC in a manner that duplicates whatever the CDS3 does in this regard? Ultimately, it's the analog output of the DAC circuit that feeds the pre-amp regardless of whether it's inside the CDS3 or inside a dedicated DAC component. So whatever happens up to that point is the critical piece, right?

Somehow I see the days of the CD as numbered in a much different way than the pundits said the days of the LP are numbered when CDs first hit the market. Since the data on CDs is all digital, I can't see how the storage media can ultimately make any difference as long as all the data is there.

I'm looking forward to this technology progressing, I think it's unavoidable. Even for high end digital audio.

-Peter

 

In my case I have to say yes it will. I like to think my setup is fairly high end and I am now convinced that a well setup PC/Squeezebox/DAC frontend will do all a CDP does and more.

One has to question the cost. Yes a SB is cheap but a PC & DAC aren't. I started this thinking that replacing my CDS2 with a CDS3 was expensive (it is) so using my existing PC keeps the copst down but if you are starting from scratch you'd need a PC £500, HDD £250, Squeezebox & bits £300 & DAC £2000; all in all the same price as a good CDP.

I understand the theory as to why Naim keep their DAC close to the transport, less chance of nasty interference etc but I'm not sure how that applies with a PC as the packets are nothing special until they hit the Squeezebox. So keeping the signal path between the DAC & the Squeezebox might be important.

 

to echo toms thoughts and to answer your question.
in my case i have replaced a fairly high end (to most normal people) cd player - naim cd5 / hicap with a squeezebox / dac. i auditioned a variety of very expensive cd players from a naim cdx2 to a top of the range sim audio and cec transport / dac and still went for the pc solution without feeling i'd compromised on quality. also 2k for a dac is a bit ott imho. there are solutions out there in the 500 to 1k price range which will sound fantastic. as most here already have a pc i'd not include that in the cost.
at 100 quid for a 250gb hdd, 140 quid for a wired squeezebox (both from dabs) and a dax 2 for 500 quid you've spent 750 quid on a system that will 'shite from a great height' on a lot of more expensive digital replay solutions (imho of course).
cheers


julian

 

Bingo!

That's exactly what I thought.

So given a PC with suitable HD space and the media hub device all networked nicely together, the DAC becomes the critical piece. Now this all makes sense to me.

As far as the cost being comparable to a more conventional setup, perhaps. But...there has to be some value in the flexibility afforded by the jukebox over manually loading up a CD.

So...assuming this is all technically sound...how would a company like Naim (or any other high end CDP maker) plan for the future? They have a great DAC already (let's say CDS3) but now the transport becomes perhaps redundant. If they make the decision to sell the DAC separately due to market demand, how can they sell it for anything even close to the price of the full CDS3?

-Peter

 

Good to hear. Do you (or anyone else) have a good source for DAC comparisons, reviews, etc. I know julian you are advocating older DACs but I'd like to do more research on my own if possible.

-Peter, getting closer to making the plunge

 

plz,
ok i think perhaps you are oversimplifying.
a network audio system will go through the following stages (not including ripping).
1) reading the data off the hdd and transfering it over the network to a ram buffer in the media device. this ram buffer allows for network errors, dropouts and lag.

2) the data is clocked out of the ram to the digital output and squirted down the interconnect to the dac

3) the dac recieves the data and converts it to an analog signal.

stage 1 happens so quickly and the ram buffer holding everything means that jitter isn;t a factor.

stage 2->3 is where jitter can occur - basicly errors and interference with the clock signal transmitted with the data.

stage 3 can also introduce jitter if the dac reclocks the signal badly.

with a traditional cdp stages 1 and 2 are combined. naim claim the in order to reduce jitter between stages 2 and 3 the transport and dac should be in the same box and close together in order to minimise interference.

as for the price of a hypothetical cds3 dac. well in order to perform the same you'd still need 2 boxes to keep the psu seperate along with all the attendant costs. also mechanical isolation would still be necessary along with the 50 or so stages of regulation that happen inside the box(es). so it would still cost a fair bit. still, i recon you can do better for less though.

 

plz,
just get out there and hear them for yourself. this is how i came to my older / multibit conclusions - although i did like the cec dx71 dac which is a delta sigma 96khz device. the other thing i like is hefty psu's (i run naim kit also so have found this with pre's and my original cd5 / hicap).
i actually bought the dax 2 blind (deaf ?) however it has 3 seperate transformers (dual mono for the analogue and 1 for the digital) 36 regulated power rails, 20bit 8x overampling dual differential multibit converters and selectable filters (hdcd and npc 5842) which again ticked all the boxes so i felt it worth a punt. the fact i got it direct from dave heaton at a/s with a 1 yr garuntee on a 1 week trial were better. also seeing as they were on sale 2nd hand for nearly 900 quid and i got it for 500 meant i could have sold it and made a profit clinched it.
the other one i was tempted by was the msb platinum link dac which has a totally bespoke hard wired dac however sourcing a 240v version for anything like sensible money is a 'mare.
other dacs worth a look / listen are:
various wadia's,
the NOS dacs - audionote, 47 labs, scott nixon, etc.
chord dac 64.
DPA dacs - old but good sounding - may be flaky though
some swear by older meridian dacs - not my cup of tea though
C.E.C. dx 51 / 71
California Audio Labs tube dac's
Bel canto dacs
Camelot audio arthur (?) is reputedly good.
Perpetual technology dac / upsampler / psu
other A/S dacs (decade and ultra analogue dax, discrete if you're loaded)
there are also a number of cd players out there that can act as dac's - the sim audio moon for example.
cheers


julian

 

MP3 is the bastard offspring of Dolby B! :slayer:

Save your (hi-fi) soul while you still can and use FLAC or APE for lossless compression onto a HD.

This may have already been mentioned; both are excellent audio codecs and available here http://www.dbpoweramp.com/

As for a good and reasonably priced DAC try the M-Audio Flying Cow.

24 bit delta-sigma conversion for £149. http://www.dolphinmusic.co.uk/d2/page/shop/browse/category_id/1d13065590cd8fe87f31bf6fce1fc155

 

Guilty as charged

julian, thanks for all your info (Tom A too). Yes, I suppose I am simplifying but still, the real gist of my comments is that the source of the digital data is no longer confined to a factory CD. As long as all the original bits are there and the media hub can properly (that is: complete, error-free, correctly timed) transmit the data to the DAC, it doesn't matter where the data bits came from. And the jukebox offers vast functionality enhancements over a conventional CD player. Not to mention the aesthetics of not having to keep the CDs in the general area of the hi-fi (I prefer a minimalist look).

Ok, I see. So perhaps because the transport itself is a third party device (Phillips?) and presumably not a big part of the overall cost of a top CD player, the cost of the DAC version of such a CD player might be very close in price to the full feature player? I guess that makes sense.

Oh, and thanks for the DAC suggestions. I think some auditions are in order once I get a few CDs ripped to disk.

Thanks again for all the info, great stuff!

-Peter

 

mosfet, I am only talking about lossless storage. In fact I would probably opt for WAV so not only lossless but uncompressed. HD space is dirt cheap and the prices are only going in one direction as far as I can see. No sense adding extra processing to the equation.

Thanks you for the DAC reference, I will investigate.

-Peter

 

peter,
theoretically 'bits is bits' whether they come from a cd or a hdd however as jitter is primarily an issue between transport and dac (hence naims insistence on keeping the distance between the two to a minimum) the quality of this interface and the clock controlling things is important.
the squeezebox has a pretty good reputation for jitter performance but as i posted a few posts back there are differences in the quality of the output differeing between flac and mp3 playback leaving room for improvement.
all that said - it's really splitting hairs and can pretty much be ignored.
cheers


julian

 

julian,

You mentioned that you were experiencing some problems with the Squeezebox compared to MP3 data. Any chance this could be related to the fact the SB is decompressing the FLAC data? Have you tried uncompressed to see if that makes a difference?

-Peter

 

I have a Roku box, but I'm using the slimserver. In my setup, FLAC is decoded on the server to uncompressed, whereas, MP3 is sent as is, and is decoded on the Roku box.

 

"As long as all the original bits are there and the media hub can properly (that is: complete, error-free, correctly timed) transmit the data to the DAC, it doesn't matter where the data bits came from..."

Ahh ha ha a ha ha ha ha ha.

Excellent, you have just in one sentence fixed a problem hifi makers have faced for years, well done!

 

My setup is Powerbook sending uncompressed WAV files via firewire to M Audio Audiophile Firewire which outputs SPDif into the Dac Section of my CD player.

Sounds great! Slightly different to the CD player, but no better or worse. Wireless with the Airport sucks though, as does Apple Lossless and all the other processing.

 

plz,
as oedipus says, the server decompresses the flacs to wavs and then sends these to the squeezebox. wharease with mp3's the mp3 data is sent to the squeezebox and decoded locally.
although the 'problem' is not really that huge, it does point out that an improvement (although how large i don;t know) is possible.
there are a number of things that could cure this problem. originally i thought it may be due to me using the squeezebox in wireless mode however i'm now using it wired and there was no improvement. i've also upgraded to the latest version of the server software and sbox firmware and this didn;t improve matters - although it did cause some other unrelated problems with dropouts which took a while to find a fix for.
i'm guessing that there are 2 remaining areas to try to fix the problem

1) improving the interface between squeezebox and dac. to this end i'm looking into jitter reduction devices (a monarchy dip initially) which also converts to aes / ebu digital. hopefully i should be borrowing one of these in the near future to see if it fixes my 'problem'. if it doesn;t i may try to source a genesis digital lens and see what that does - or i just might say fcuk it and buy some more music.

2) the pc itself may not be powerful enough. this is really a last ditch hope and quite unlikely as having looked into the processor load it's peaking at around 30% every 10 seconds or so whilst averaging around 5% for the rest of the time - even though it's a lowly p2 400. memory is the big thing for this application and i've recently upped the memory from 64mb to 320mb so this doesn't seem to be an issue any more.

as i say the problem is more an irritation of my audiophool sensibilities - i.e. knowing that i'm perhaps not eaking the last iota of performance from my kit however flacs still sound far better than the mp3's i have crystal lock or no and still sound better than the majority of cdp's i listened to when searching for a replacement to my cd5/hicap.

cheers


julian

 

Thanks for the clarification. Good luck tracking down the last issues.

This thread (and others I've since dug up here and on pfm and the Naim forums) has given me lots of startup info on what's out there. My CDP upgrade is definitely on hold.

Thanks for the great information!

-Peter

 

Julian, I too use a wireless Squeezebox, in a Linn system, over a 802.11b network with a lowlyish PC in another room, and you raise a few questions that I would appreciate yours and others thoughts on.

1st, what is the "problem" you refer to in #37 - do you mean simply that there might be room for improvement for pple who use mp3 (like me).

2ndly, were you thinking of the loaning the classic Monarchy dip for jitter reduction, or the upsampling version? I was thinking of the classic myself - do you know of a European supplier? I'd appreciate hearing the results of any tests.

3rdly you mentioned dropouts. I get these 'pauses' every hour or so and I can't narrow down what setting affects it, but I think it could be the time when the software writes my on-the-fly iTunes star ratings to the database. Can you pinpoint how to reduce or eliminate them?

 

steve,
the 'problem' is with flacs than wioth mp3's - basically i get better jitter performance with mp3's than with flacs.

afaik it's an older model and not the upsampling version. i'm not a big fan of upsampling. i'll post the results up when i have them. the one i'm borrowing is from a private seller.

the dropouts i got were cured by (iirc) changing the server>behaviour>save history option to 'dont; save history' also for good measure i stopped nay other remembering of stuff as well. i don;t synch with itunes though as it strikes me a bit like hobbling a reasonably well designed system with the monster that is itunes.
cheers


julian