Best Way To Output From USB

[richardfinegold]

I've been burning many CDs to a hard drive in an effort to reclaim real estate. I play the music back from an external HD that connects to a Mac Air via Thunderbolt. The Air connects via USB 3.0 to my DAC
(which is the digital input of my Oppo 105 Universal Player).
Previously to purchasing the Oppo I was using a PS Audio "Digital Link" DAC that sounded great via SPDIF but did not do asynchronous USB. I added a Musical Fidelity "V-Link" that converts USB to SPDIF
and that improved things for USB. I later added the Oppo so that I could play Blu-Ray,SACDs, and DVD-A.
The Oppo as a DAC is great with Coax and Optical, and with flash drives. I am less entranced with the direct USB connection to my Air. It isn't terrible but there is a noticeable drop in quality, as if the proverbial veil has been pulled over the music.
I note with some amusement that in reading Audio magazines, many Audio reviewers that had previously praised computer audio and USB in particular to the skies are now rating the USB inputs of many DACs as inferior to their other digital inputs so apparently my perceptions are not unique.
When I restore the "V Link" to the system things improved, and life was good, but now I am getting many dropouts that I have determined are due to a loose USB connection to the V Link. This loose connection does not happen when I use the same USB cable on USB inputs of other components so I think the problem is shoddy workmanship in the V Link, which was after all a budget item.
How have others here obtained the best sound from their computers?

[Gordon]

As no one else has here's my tuppence FWIW!!

I can’t offer any direct help rfg because I don’t use a USB link that often but perhaps I’ll hazard a comment or two. The possibility of a duff connection is always present. You don’t say more about what these “drop outs” are and what they sound like. Does the audio mute to silence or what? Is the audio continuous behind the drop out or does it stutter? The loss of physical connection might result in a loud plop at least if not worse? A drop out is more consistent with the DAC running out of data and/or timing issues on the USB transfer through the USB host in the Mac.

Your description of a veiled sound doesn’t sound like gross data loss but something more low level. It could be related to clock timing. It is well known that DACs need tight jitter specs so I wonder if what you have is a bit of jitter intolerance? Perhaps your VLink device has better tolerance to the USB jitter than the Oppo? Whilst the S/PDIF and USB specs provide some detail, manufacturers are free to enhance their products from a baseline that may be adequate for consumer purposes but not for audiophiles? I have not found a DAC spec yet [still searching] that gives enough detail about jitter tolerance - in particular how much INPUT jitter is acceptable.

I assume that you have looked at what the manual of the V Link says about USB connections. The MF web site only offers this sparse spec in the manual here but do look at the Troubleshooting tables on page 2 about drop outs.



It states: See “additional USB information” section. This section states:

Additional USB information
On the host computer, a new mixer will be available, which is the default
mixer whenever the DAC is plugged in. Use this mixer to select the
source or adjust levels if required. CD, MP3, WAV files played on any
software should now play through the DAC. This device has been
designed to work with Windows XP, Windows VISTA, Windows 7 and
Apple OS X onwards.
The computer drivers for the USB input of the V-LINKII should install
automatically.

Mac users
....................text omitted..........
This device is a high speed serial data processor, and by its nature,
requires a very high volume of USB bandwidth. It will benefit greatly
from being the only device connected on its USB ‘port’. Sharing the
same port with other devices may cause unwanted artefacts such as
dropouts or temporary loss of signal. This especially includes the use of
the DAC on a USB hub/splitter alongside other USB components.

It might be useful to look at this link and its sisters on the same site; if you look to the left half way down this page you'll see a link to how to use USB with MAC OS X:

http://www.anedio.com/index.php/article/measuring_jitter

[richardfinegold]

As no one else has here's my tuppence FWIW!!

I can’t offer any direct help rfg because I don’t use a USB link that often but perhaps I’ll hazard a comment or two. The possibility of a duff connection is always present. You don’t say more about what these “drop outs” are and what they sound like. Does the audio mute to silence or what? Is the audio continuous behind the drop out or does it stutter? The loss of physical connection might result in a loud plop at least if not worse? A drop out is more consistent with the DAC running out of data and/or timing issues on the USB transfer through the USB host in the Mac.

Your description of a veiled sound doesn’t sound like gross data loss but something more low level. It could be related to clock timing. It is well known that DACs need tight jitter specs so I wonder if what you have is a bit of jitter intolerance? Perhaps your VLink device has better tolerance to the USB jitter than the Oppo? Whilst the S/PDIF and USB specs provide some detail, manufacturers are free to enhance their products from a baseline that may be adequate for consumer purposes but not for audiophiles? I have not found a DAC spec yet [still searching] that gives enough detail about jitter tolerance - in particular how much INPUT jitter is acceptable.

I assume that you have looked at what the manual of the V Link says about USB connections. The MF web site only offers this sparse spec in the manual here but do look at the Troubleshooting tables on page 2 about drop outs.



It states: See “additional USB information” section. This section states:

Additional USB information
On the host computer, a new mixer will be available, which is the default
mixer whenever the DAC is plugged in. Use this mixer to select the
source or adjust levels if required. CD, MP3, WAV files played on any
software should now play through the DAC. This device has been
designed to work with Windows XP, Windows VISTA, Windows 7 and
Apple OS X onwards.
The computer drivers for the USB input of the V-LINKII should install
automatically.

Mac users
....................text omitted..........
This device is a high speed serial data processor, and by its nature,
requires a very high volume of USB bandwidth. It will benefit greatly
from being the only device connected on its USB ‘port’. Sharing the
same port with other devices may cause unwanted artefacts such as
dropouts or temporary loss of signal. This especially includes the use of
the DAC on a USB hub/splitter alongside other USB components.

It might be useful to look at this link and its sisters on the same site; if you look to the left half way down this page you'll see a link to how to use USB with MAC OS X:

http://www.anedio.com/index.php/arti...asuring_jitter

Thank you for your reply Gordon, and the effort that you e
devoted to it. After reading your posts on the Pristine Audio link, and now this, I feel very lucky that I am able to call upon you as a resources.
Since my OP I have tried placing the V Link in other positions in the equipment rack and that seems to have solved the dropout issue. The USB connection simply isn't the tightest and any change in the position of the v link can cause an interruption, but the present position seems to be curing that for now.
The "veil" that I refered to in my OP was the sound of the Mac Air connected directly into my DAC without the V Link. Compared to the other inputs on the DAC, including the USB Flash drive inputs, there is a loss of vitality to the sound. The V Link improves the situation, presumably by removing some jitter.
Many other USB interfaces that are out there, such as Empirical Audio Off Ramp and Berkley Audio USB Interface, cost more than the price of my (Universal Player) DAC, which seems absurd to me. The MF at least costs a fraction of the DAC but has the issues mentioned. I was wondering what others were doing to output USB, as I intend to rely on this this interface more as I burn a few thousand CDs to a hard drive.

[Gordon]

Glad to have been of service rfg although you seem to have solved the problem yourself. I am a bit surprised that there was no other response to your OP!

The message is: the computer environment and data handing processes are not designed specifically for high quality audio, especially in the area of timing control. After all, all you are doing is shifting some bits from one place to another in real time. What could be so difficult?!!

[richardfinegold]

Glad to have been of service rfg although you seem to have solved the problem yourself. I am a bit surprised that there was no other response to your OP!

The message is: the computer environment and data handing processes are not designed specifically for high quality audio, especially in the area of timing control. After all, all you are doing is shifting some bits from one place to another in real time. What could be so difficult?!!

I read a post yesterday in an audiophile forum by the engineer that runs Empirical Audio. His contention was that a USB Interface should cost more than a DAC, because in his opinion it does most of the work extracting sound from USB.
Personally, I wish that computers would come with SPDIF, but only specialty computers do so.
Firewire was a far better interface than USB but never caught on and firewire DACs are rare beasts indeed.
Many laptops have HDMI outputs, and some DACs now have HDMI inputs, but that is another high jitter prone interface that i would be leery of.

[Gordon]

I read a post yesterday in an audiophile forum by the engineer that runs Empirical Audio. His contention was that a USB Interface should cost more than a DAC, because in his opinion it does most of the work extracting sound from USB.
Personally, I wish that computers would come with SPDIF, but only specialty computers do so.
Firewire was a far better interface than USB but never caught on and firewire DACs are rare beasts indeed.
Many laptops have HDMI outputs, and some DACs now have HDMI inputs, but that is another high jitter prone interface that i would be leery of.

Well, all those alternative interfaces were designed for data transfer in an IT/IP etc environment. I doubt that the exacting requirements of high quality audio figured prominently in their design. At least HDMI has to carry video/audio streams but that environment [TV set etc and player] is somewhat more controlled.

The engineering involved in HQA interfaces is not hard as long as one is aware of what one is trying to do. Any fool can knock up a data path that "works".....Doing it properly in a practical environment takes a bit of thought and care, that's all, but that takes time and costs in R&D time and in build quality!! Your man from Empirical Audio sounds as though he has done some thinking!!

There is an awful lot of fine detail in engineering digital HQA all the way from initial sampling through quantising, format changing etc to DAC building. Non technical people can get hyped up [by some journos eg] on specific things like bit depth but are unaware of other factors, especially the practical ones rather than the theory, that in some cases can do far more harm than short bit depth. One needs an holistic approach; one cannot speak of things in isolation. The wet can get in right at the start with an ADC whose sampler isn't well implemented which gives the quantising stage and everything else that follows no chance. I have found very little on the web about implementing samplers but a great deal about sample rates.

[MrGongGong]

Interesting stuff
In the world of live electronics and diffusion Firewire has been long preferred over USB which was always prone to "falling over"
There are several hybrid interfaces that many folk use (MOTU etc) which will have both USB and Firewire
but the manufacturer of choice these days seems to be RME (http://www.synthax.co.uk/products/pr...-catalogue/rme) which is what I would jump at if I had the cash.
It does seem to me that many folks buy very expensive "domestic" kit which costs more than the equipment used to make the recordings they are listening to in the first place ! which is a little odd IMV
If you really are after super high quality then buy 'pro' gear !

[Gordon]

It does seem to me that many folks buy very expensive "domestic" kit which costs more than the equipment used to make the recordings they are listening to in the first place ! which is a little odd IMV.

Quite so MrGG!! - that's horse sense!! [Sorry, couldn't resist ]. Thanks for that link. I love the Babyface product!! And that Trade Mark: SteadyClock(TM) speaks volumes about the loose nature of the spec'ing of "standard" USB etc. Why the need to do that special processing if the thing was well spec'd in the first place?

It's interesting how the large sums of money made by the likes of Google, Microsoft, Cisco, et al have been used to buy media technology companies after they realised that capturing and shifting high quality video and audio around wasn't like shelling peas [eg like from an iPod!! Get it! No? Oh, well].

[richardfinegold]

Interesting stuff
In the world of live electronics and diffusion Firewire has been long preferred over USB which was always prone to "falling over"
There are several hybrid interfaces that many folk use (MOTU etc) which will have both USB and Firewire
but the manufacturer of choice these days seems to be RME (http://www.synthax.co.uk/products/pr...-catalogue/rme) which is what I would jump at if I had the cash.
It does seem to me that many folks buy very expensive "domestic" kit which costs more than the equipment used to make the recordings they are listening to in the first place ! which is a little odd IMV
If you really are after super high quality then buy 'pro' gear !

I just would like to see the USB input not have a noticeable drop in quality compared to the other DAC inputs, since out of necessityt, USB has to be the prefered way to get audio out of a computer.
Right now the V-Link seems to be a workable relatively low price fix.