Hi and welcome to the forum.

I've been using the Logitech Squeezebox line of music streaming devices for over 6 years now and i can safely say that I don't miss CDs or SACDs or DVD-Audio discs one bit. There could be quite a few reasons why you not getting the best possible sound from your computer and streamed audio. First and foremost: Windows Media Player is completely worthless. Stop using it at once. Pure garbage, in fact it is so bad that it actually makes iTunes seem like a good program. For what it's worth iTunes is a very close second to WMP is the POS department.

Anyway I strongly suggest that you download the latest version of Foobar and then do a little research to find out how to enable bit perfect playback via Foobar. Since, as stated, I use Squeezebox devices I'm not personally familiar with all the setting of Foobar but I know that it is considered the best audio player for windows computers. Plus I am not familiar with the Sony Media device you are using but based on the results you are getting I would guess that this device may also be causing some problems.

You might also want to check that you are using the latest USB drivers for the Cambridge Audio DACMagic Plus since non-Asynchronous USB can result in less than perfect playback.

Finally try ripping a few CDs into flac files using Exact Audio Copy (EAC). Again I will have to ask that you do a little research on how to set up EAC to get accurate rips and proper wav to flac conversions. By the way rest assured that there is plenty of good information readily available for Foobar, EAC and flac so it should not be that difficult to get everything properly set up. Once you have a few good CD rips, properly encoded flac files and Foobar I think that you will not be able to notice any difference between computer playback and CD playback.

...between a bit-perfect rip and bit-perfect replay.  In my experience most of the problems folks experience with PC audio are to do with their replay settings rather than their rips.  Remember, a ripping error will almost always manifest itself as a noticable "click" or worse, not a subtle sound quality degradation. 

You need to make sure that the media player is just decoding the file and passing the PCM samples along to the DAC, nothing more and nothing less.  The easiest way to destroy the fidelity of a digital file on replay is to apply too much digital attenuation.  Each bit equates to about 6dB so as you reduce the volume you lose resolution.  So the No.1 rule is to play back at full volume on the PC and adjust the volume in the analog domain on your amp.

Then there are plug-ins that can cause mischief if present, things like "replay gain" that try to equalise the volume between songs etc.  Make sure any such are disabled or uninstalled.

The other common gremlin with PC playback is RFI, particularly from the computer itself being transmitted through ground planes (this can happen with USB as well as S/PDIF connections).  Experiment playing back with the laptop on its charger versus on battery, and plugged into the same distribution block as the component (e.g. DAC) it is connected to.  I wouldn't mind betting that one of these will sound clearly better than the others.

The above advice all applies primarily to the PC.  I'm not quite sure where the Google box comes in since you said you are replaying via WMP.  I assume the PC and the Google box are alternative digital sources, right?  The same point about digital volume control and possible plug-ins apply to the Google box, although not the point about ground-borne interference since you said you are using an optical connection.

..except for the bit about buying a better soundcard for your laptop.  I checked out the DACmagic + online and it looks pretty well thought through - even has a ground lift switch for dealing with ground loop problems!  Connecting this to your laptop with USB obviates the need for a soundcard.  As long as the USB driver under Ubuntu works (the Cambridge Audio website says Ubuntu is unsupported but known to work) then you should be good to go.  Ripping CDs losslessly to FLAC and replaying at full digital volume via foobar with no sound altering plug-ins through the DACmagic + via USB I would expect you to enjoy sound quality way better than any correspondingly priced CD player.  

However rereading your original post it isn't quite clear to me whether you were comparing the laptop versus the Luxman both via the DACmagic (i.e. using the Luxman as a transport only)  or the Luxman versus the laptop + DACmagic (i.e. using the Luxman as a CD player).  I suspect your Luxman cost a deal more than the DACmagic +, depending on which model it is maybe as much as an order of magnitude more, so if the latter I think you have to ask yourself to what extent this is a fair comparison.  If the former I would expect the sound to be pretty similar.

Mayfield 4 wrote:

So big question - if I use the dacmagic, are you saying the computer sound card is unnecessary? So if I were to buy a better sound card I wouldn't notice an improvement?

I would have said yes, i.e. you wouldn't notice an improvement, but since your last post I am less certain (please remember I have never heard the DACmagic + so my opinions and advice regarding it are entirely theoretical) .  That advice is predicated on the assumption that the budget has been apportioned equally between the S/PDIF and USB inputs and they sound more-or-less equally good.  If in practice the former sounds better then of course that assumption may not be valid.  A soundcard with a high quality S/PDIF output may well in that case level the paying field against the Luxman.

However I can't help thinking that the comparison is anyway skewed.  If the Luxman cost $3-4-5k then it plays in a completely different league to the DACmagic.  Spending that kind of money you would be able to afford a really good asynchronous USB DAC that would very probably best both on SQ grounds (I am thinking something like an Ayre QB-9, a Berkeley Alpha DAC, Calyx 24/192, Mytek 192-DSD, T+A DAC8, or many many others).

The DACmagic is a competent $400-ish product, but even at that price level there are arguably better products (for instance the Arcam rDAC).  So I still think spending money on a soundcard is probably the least effective use of funds here.  Why not sell the DACmagic and the Luxman (if you are prepared to abandon optical entirely - I did 7 years ago and never looked back) and get a really decent USB DAC.  Alternatively be happy and spend it all on CDs!!

Maybe not what you wanted to hear but I'm just calling it as I see it.

I don't understand why you think you need a new PC or a soundcard.  I checked out the Ken Rockwell review of the DAC magic and even if he makes a whole raft of very strange claims it was interesting to see his measurements.  The RCA S/PDIF input of the DAC magic does indeed seem to be the cleanest, but both the optical and USB inputs seem to perform well too.

So if you're happy with the DAC magic (and I'm not for a moment suggesting you shouldn't be, I'm just a bit baffled why you spent so much less than I am guessing you spent on your CD player yet expect it to perform as well) then I think your most cost-effective upgrade maybe a USB-to-S/PDIF converter such as the Halide bridge as reviewed by JA here.  That way you can use your existing laptop to feed the DAC magic's best quality input, and I would expect it to give about the best sound the DAC magic is capable of delivering.

By all means get a new PC if you feel you need one, but although it may bring you all sorts of ther improvements, it hardly focuses he funds on sound quality improvement which is what I think you are trying to achieve.

And to answer your question, yes, the only thing a soundcard does when used with an external DAC is serve up the bits.

I'm afraid I have confused things a bit here by answering questions with too little information, would have been simpler if I asked you to explain the background from the get go.  Sorry about that.

Despite my confusing explanations I think you have mostly got the right end of the stick.  Let me see if I can summarize:

1.  A well implemented DAC is more important than a well implemented transport.  A well implemented DAC will ignore or correct sources with high levels of jitter.  This is one of the few cases in audio where garbage in doesn't necessarily equal garbage out.  So before spending a lot of money on a transport you should spend as much as you intend to on a DAC.  Once you have the DAC of your dreams a better source can still improve the sound, although maybe only marginally depending on how well your DAC rejects jitter.

2.  There is a way of implementing a digital connection over USB that enables a very low jitter connection from just about any USB host.  It is called asynchrounous USB, DACmagic plus has asynchronous USB.  An asynchronous USB connection from a completely standard laptop can have less jitter than a S/PDIF connection from a high quality transport.  This has nothing to do with which version of the USB standard it is running over, USB 1.1 at 12 Mb/s is ample for CD-resolution material and more bandwidth doesn't improve things.  However USB is a bus, anything connected to it can use it, so the more devices you have hooked onto the bus the more contention there will be for that bandwidth.  In that sense dedicated audio compluters have an advantage, because the audio doesn't need to share the USB bus with a bunch of other devices.  USB disks are the worst because they transfer lots of data.  Connecting an external disk with the music on over USB and using a USB port on the same controller for the DAC connection is the absolutely worst scenario.  The data coming off the disc will be fighting the data going to the DAC for bandwidth. 

- Implication for you.  Since DACMagic plus has asynchronous USB so you should be able to get good sound from this input, even from your USB 1.1 laptop, and avoid any expense associated with high quality S/PDIF sources.  The Halide Bridge has a very high quality asynch USB input and a S/PDIF output so will effectively turn any DAC into a high quality USB DAC but on reflection I don't think it would be the right product for you, especially given the price of the Halide relative to the price of your DAC. 

- Implication for you.  You should be able to get decent sound via the USB connection, even with your existing laptop.  Remove any other USB peripherals and check the factors I mentioned earlier (full-resolution rips, full digital volume and no sound-altering plug-ins).  Does the Luxman still sound better??

3. If you are using a DAC the only thing the source component does is supply the bits.  Since most digital sources are bit-perfect (CD player unless the disc is damaged and PC if it is set up right - per earlier posts) then the only influence the transport can have on the sound quality is the amount of jitter in the signal.  Okay, some people believe there is something else influencing sound quality that we haven't discovered yet and I can't disprove that, but until we discover it i suggest we ignore it.

Implications for you:

- If one source sounds better that another on the same DAC input it is likely the better sounding one sounds better because it has less jitter.  Remember, jitter is very hard to measure properly and specs are likely to be misleading.  Home trials and comparing by ear is the only really reliable way to decide here.

- If one source sounds better than another on different DAC inputs then either it has lower jitter or the better sounding input is just better implemented in your particualr DAC.  Which of the two is pretty much impossible to ascertain so don't waste energy speculating about it.  It's just the way it is so accept it and act accordingly.

4.  A sound card typically has analog inputs (ADC) and outputs (DAC) for two, four or more channels.  Some additionally offer one or two (RCA and optical) digital outputs.  On a typical soundcard a digital output will be one very small piece of functionality that will account for a miniscule fraction of the cost of the card.

Implications for you:

- By all means get a new media PC, just don't bother to specify a soundcard if you only intend to replay via a USB DAC. 

- USB 2.0 vs 3.0 makes no difference at all for the audio stream (altough of course USB 3.0 is much faster which will improve the performance of other peripherals like discs but the additional bandwidth offers no benefits for audio fidelity). 

- However do specify at least two USB controllers (USB 2.0 or 3.0) so you can use one for connecting to the DAC and one for other peripherals (mouse, discs, BD drive etc.)

Summary:

Even though the measurements showed the RCA S/PDIF to have lower jitter than the USB in the tested configurations both were very good.  You should be able to get good sound from your existing PC over USB 1.1 if the rips are good and the replay environment is properly optimized.  If you try this and are still unhappy then you can start throwing money at the problem!

Hopefully this will help you decide your next steps.  Sorry for muddying the issue!

..but the test you mention above certainly doesn't prove it. 

If I've understoood it correctly you're comparing your laptop with a completely different computer running a completely different media player, operating system, and USB device driver (essentially all the software and firmware the digital audio is passing through is completely different) yet you ascribe the difference in behavior, more-or-less arbitrarily as far as I can tell, to the different USB versions. You might just be right, but this is what an engineer would call "selective cause-effect linkage". 

Moreover 24/192 program requires 9.2 Mb/s of bandwidth, and USB 1.x is certified up to 12 Mb/s, so in theory bandwidth shouldn't be a problem (especially if the DAC has the USB controller all to itself, per earlier posts).

I would suggest posting on Cambridge Audio's forum (assuming the have one) and asking if any other customer is successfully able to play hi rez material over USB from a PC running Ubuntu before you dive in and buy a new machine.

Glad you're making progress anyway.