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[Russ Reed]

Hi all!

How can you tell which USB port is the best choice for audio out? At present I'm using a Vista OS laptop
for a music server ( soon to be replaced I hope ). I've looked in the device manager and it lists 4 hubs. 2 say enhanced and 2 say open. There are only 3 USB ports on the computer. 1 is on the right side next to the power plug. The other 2 are on the left side. Anyone know how to tell which port is unshared and the best choice to plug in a DAC?

Thank You, Russ

[Russ Reed]

Gordon at Wavelength said to download a Windows program called USBview that will map the USB ports on a PC.  Use About this MAC on MAC books.

Most everyone else on the ComputerAudiophile forum said to listen to each one there will be an obvious difference.

Hope this helps. Russ

[Matt]

Gordon at Wavelength said to download a Windows program called USBview that will map the USB ports on a PC.

What are you looking for in USBview?

I assumed that it wouldn't matter what USB port you selected.  Isn't that sort of the point of using a digital connection like USB?

[Russ Reed]

No Matt, some USB ports are shared with other things like a keyboard or mouse. If you can locate an unshared or master USB you should hear a noticeable difference. I haven't downloaded USBview yet. I'm going to just listen to all three ports first, then if need be, try USBview. Just search USBview and you will see an example.

Most everyone including Steve at Arye said just listen that you would hear the difference. Russ

[JimH]

I don't think that's the case.  If USB ports weren't distinct from each other, devices would corrupt each other's communications with the computer.  You would never be able to print a photo, for example.

[Russ Reed]

Jim, I think what they mean is it's just enough to cause a sonic difference. It's has to do with the origination point of the port internally with the motherboard. Some come off at the same point as do the keyboard connection or others. Locate the unshared port and it suppose to sound better. Everyone from Wavelength to Arye says it is obvious. I'll have to listen to believe myself. Russ

[JimH]

I just don't see how.  The digital stream from MC is a series of 1's and 0's.  The driver delivers it to the DAC.  Nothing else should be heard unless the equipment at the DAC point is adding noise, and in the case of Ayre or Wavelength, the DAC only knows it's receiving 1's and 0's.

If one USB port were affected by a device on another USB port, then USB would be a mess.

[Russ Reed]

Jim, this will help.

Read Chris's article and Gordon's comment about USB in this thread.

http://www.computeraudiophile.com/content/USB-Port-Not-USB-Port

I'm no expert, this is where I got my info. Hope it helps anybody with improved sound with a USB DAC. Russ

[JimH]

Thanks.  I took a quick look.  It's not possible, in my opinion, to know what was happening.  I do acknowledge that a USB port can be flakey or even not work, but that's not what I thought you meant above.  If the power deviated from the spec, it certainly could be audible.  But that's just bad hardware, and doesn't mean that all USB is suspect.

Keep in mind that USB is reliable enough that many external hard drives use it.  If it were generally flakey or prone to errors, these drives would be useless.

I respect both Chris and Gordon's knowledge, but I don't agree that, for example, most USB ports on the front are unreliable.  

Wikipedia has a good article on the USB standard.

[wavelength]

Guys,

Jim/Matt... Russ is totally correct here.

See hard drives use Block mode which is error correcting. Therefore if you put a USB hard drive on the wrong port it basically slows down compared to other ports but people really do not see this as an issue.

But audio uses isosynchronous protocol which is non correcting. Therefor the port can be critical. The biggest problem is which one?  USBView is a crap program and you can use the Device Manager to see the USB tree but neither are great tools.

For instance.... NEVER use the USB port on the front of the computer. These are usually strung from some cheap a*** ambilical cord and lucky to support a keyboard let alone audio.

Same with some laptop ports... in some cases like Dell for instance nothing seems to work. Dave Clark from Positive Feedback magazine had a Dell that could not even stream correctly at 44.1/24?

Most of the Laptops have 2 ports on the mother board side then they dangle another one on the other side which is usually the one shared with internal peripherals such as:
1) Camera
2) Keyboard, track pad, ibm joysticky thing
3) Bluetooth
4) Audio

Most of the Intel Bridges have a 2 or 4 port main hub and then all computers usually take one of these ports directly out which is your best bet.

~~~~~~~~

Now for the real kicker... HUB designers now have what are called load leveling intelligent controllers. This is where each USB port that is enumerated (the process whereby the device tells the computer what it is) is evaluated with the other loads and the priority and level of throughput is determined and set for that port.

This is a good bad situation in that a) it makes it easier to find a favorable port... but b) if you have a lot of other crap attached to this controller things go south.

Anyways, there you have it!

Russ enjoy your QB9 it's a great piece!

Thanks
Gordon
Wavelength Audio

[JimH]

Gordon,
I don't disagree that some ports won't work.  Using a hub would be more likely to cause problems.  But I can't agree on front vs. rear ports.  It depends on the quality of the hardware, I suppose, but it doesn't take gold plated connectors to pass 1's and 0's reliably.  The cable itself is unlikely to drop a bit.  Long enough or under powered, yes, but not in normal user situations where the cables are 3 feet long.

For many years, JRiver did (and still does) network software.  We started with serial in around 1985, then shifted to TCP/IP networks.  With serial, we used to use crappy telephone cable on 50' runs to set up terminals that ran reliably at 115.2K baud with and without flow control.  USB 2.0 is a big improvement over what we did then.

USB ports are sometimes a problem.  I'm not sure whether it's windows or the drivers for the particular hardware.  But, in my experience, if they work at all, they are likely to work perfectly.  This is speaking from a practical, not a theoretical, point of view.  I'm sure you can run theoretical circles around me.

Hey, and, Welcome to Interact!  It's nice to have you here.

Jim

[Russ Reed]

Thank You Gordon.

Russ

[MerlinWerks]

Guys,

USBView is a crap program and you can use the Device Manager to see the USB tree but neither are great tools.


Gordon
Wavelength Audio

Hi Gordon,

Out of curiosity, what is wrong with USBView? Granted there is not much to it, but it always seemed to do what I expected it to i.e. show what devices are connected to specific USB ports. FWIW, I have an ART Legato and use USBView to ensure the Legato has a port/internal hub all to it's self.

I can see where plugging into a "busy" hub could possibly cause dropouts or something like that, but not necessarily degrade the actual audio, especially when using a device like the Legato, QB9 or Cosecant, all of which use your asynchronous transfer technology.