Importance of source quality with asynch USB DAC?

Larry,

You have a nice system! And a dedicated room!! Congrats.
How does the netbook + QB-9 sound compared to your Esoteric DV50?
Where do you store your music?
Anything to look for in the laptop/netbook/pc that could/would impact sound quality if using the QB-9?
Are you using iTunes? Anything else?

Sorry for all the questions.

Horacio

Thanks, Horacio.

I spent minimal time comparing the QB-9 and DV50. I didn't hear any obvious difference. The DV50 is still around for SACD and DVD-A.

I use a Seagate portable USB drive (350 or 500GB, cant' remember). I rip CDs on my desktop and then move the drive to the netbook. I use J. River Media player, the free version and the ASIO driver. Since the software doesn't let you store all the meta data it needs on the same disk as the music files you have to "import" new files once when moving to the netbook. It's not a big deal, at least to me. The Ayre docs on their website instructs you how to configure things. As long as you configure the software as directed and rip "securely" you should be get "bit correct" PCM output from the netbook. A portable wireless USB mouse helps a lot with the netbook also.

larry

Hi,

I used to own a Wavelength Cosecant V3 asynch USB DAC. While no computer that I tried sounded bad with it, there were some differences in sound between different computers, which tells me cleanliness of the USB output does have some effect at least with that particular DAC.

However, the differences between transports with the Wavelength were no where near as great as the differences between transports with my old MHDT Labs Havana DAC.

I think the most important aspect of a computer in the listening room is finding a computer that is very quiet from the perspective of fan and hard drive noise.

I have been plowing through this technology for about six months with the following observations:

1) A good asynchronous USB -> SPDIF interface box (I use the ART Legato) gives me the best sound for RBCD (better than either an SPDIF or AES/EBU dedicated audio card). The things the interface has to do (besides low-jitter buffered and re-clocked output) include isolating the computer from the DAC. I find streaming-mode USB interfaces and interfaces that use USB bus power sound inferior (almost always, jitter) to an asynchronous interface with its own clean power.
Interestingly, USB cables *do* make a difference; the best sound I get is from an ART cable that carries the signals but not the power lines. The presence of the power wires in most USB cables (most of which, excepting audiophile types, make no effort to shield data signals from power lines) had a deleterious effect on the interface, even though the interface made no electrical contact with the power lines. I also had an improvement from an optical USB (self-powered) cable that provided complete electrical isolation.

2) I have built three servers; one is a 'loss' in that it does not produce SQ at the level of the other two, whether by sound card or USB. I thought it was the power supply, but upgrading it did not help. The difference could be in the motherboard construction or power handling or it could be that the two much more powerful servers sound better because they have more RAM, more CPU power, and SSD for the OS (Win7). The 'loss' is a Core2 E5300 with 4GB RAM. The two better-sounding boxes are I5-650's with SSD and 8GB ram. All three use Corsair power supplies, wildly over-spec'd (650 and 850w).

Not sure we understand yet why one computer sounds better than another; laptops at least can be kept off the power lines and in many cases sound better than desktops. While I am no fan of the 'fanless' server with linear DC power (too many clocks in the PC for this to matter much), I do suspect that the more powerful processors produce better sound, especially in a Windows environment when the operating system always (always) has some busy-work to do. De-configuring services, indexing, and restore point processing is tedious and error-prone. Reduced O/S busywork in may have a lot to do with the excellent reputation of Apple boxes as music servers.

High power cpus usually do get a bad name in some circles. While it doesn't take a ton of cpu to playback 192kHz material for example, system latency may be an issue, and with a more powerful cpu maybe their are less DPCs. I have noted how driver problems caused high system latency using J. River when trying WASAPI vs. Lynx ASIO using their awesome library server over LAN. ASIO would cause high system latency and strain my low power ION board's gpu when minimizing and maxing the 1920x1080 screen - causing one click. WASAPI with same material, would result in super low system latency and no clicks or pops. It realy is amazing how well implemented WASAPI seems to be, for the most part.

This was with a dedicated gigabit wired lan connection, not wireless (which exhibited the same behavior but MUCH worse). There is this big anti-buffer, anti-power commmunity and I think it may be like Mike said, that with more crunching power you can actual better lock down everything Windows is doing. No one posts ABX tests, but hey maybe the difference when they add a linear is "night & day".

I think it's a balancing act which must be struck because at some point you are pushing the PC, such as streaming high bitrate video (mkv at 100000kbps or 192kHz audio at 3-5000kbps), closer to the edge of data shortfalls which results in buffer overruns that a DAC can't always handle (loss of sync or white noise_ because WASAPI lets the hardware and driver decide what to do with such data shortfalls (as opposed to ASIO).