Which USB port?

[Reid Malenfant]

I run a whole lot of USB devices into a 7 way powered port, the HDD that has the music is plugged into the very same (when I listen to music that is new from the laptop). That is before it gets transfered to the HDD that is connected via eSATA to the Oppo BD95 player.

When I plugged the MF V-link into the very same 7 port device I wasn't impressed, in fact I was underwhelmed, but having moved it to one of the spare laptop USB ports it is vastly better

I use Winamp to play the files.

I have no idea what is going on here, but the difference is more than surprising

[synsei]

Maybe the walwart PS has something to do with it mark

[Reid Malenfant]

Ahhhh, I see a new thread right now....

Which wall wart?


In reality you are not far off though Dave At the end of the day, all you are ever going to listen to is the power supply feeding the equipment. That is the final arbiter of the sound quality assuming the kit is good enough

[synsei]

I used to use a cheap, 7 port, powered USB port replicator. My 2tb external was plugged into it. Read/write speeds seemed to be a little slow and music files played through it sounded a bit dull. Plugging the HD into a USB port on the rear of my desktop PC solved these issues. I am sure someone will be along in a mo to spout all sorts of technical tomfoolery thus proving this cannot be. Perhaps I am going mad? That's fine, because my madness sounds better...

[Reid Malenfant]

The difference wasn't subtle.

One connection popped & crackled every so often, as I have it now it has played everything perfectly for however long it is

Hours? Yes, a few now!

Just makes me think about those USB connections They're not all the same from what I have been hearing myself, power supply or not.

[brian2957]

Perhaps you're diluting the signal by having so many draws off the single USB plug Mark. I have a laptop upstairs and used one of those 5-port thingies . When I plug in the wireless USB receiver into the 5 port USB it won't pick up the signal from the wireless router , but when I plug the receiver straifgt into the laptop all is OK .

[nat8808]

Universal Serial Bus, as the name suggests, sends packets of data along the same line, one at a time to all the devices (and some devices can be made of multiple devices too) so there can be timing errors if many many devices are taking up the packet space and also request to be treated in different ways to other devices. The buffer at the DAC end should be helping that along, but it can only cope so far.

Then, how each class of device is treated and handled and how much importance it's given is down to the hardware USB root hub chip - I'm sure some will be set differently to others and some may even be more prone to bandwidth problems depending how good they are etc. Audio/video is given it's own class number for the chip to respond to. Then there's also the layer of OS interferring too and the fact that isochronous transfer mode (that audio/video runs in) is not data-loss free (some packets will get lost).

More, if it's an asychronous DAC, then the clock signal from the DAC to the PC might be getting delayed or lost through the secondary hub or whatever and so causing a lot jitter that the PC can't latch onto properly - clock problems would certainly cause a lot of break ups and noise..

With a powered hub is it more of an active switch with some kind of influence over how data is handled too?

What would be better is some kind of parallel bus to make sure the audio data is given the full freedom of movement it needs - PCI and Firewire are two examples that are more often set up better for this from the outset (there's never anything perfect!).

Many pro/semi pro soundcards used to advise using specific PCI slots for their cards , ones that did not share the PCI bus with any other slots (this for multi-channel i/o, rather than just two track output). Have seen the same with set up instructions for USB semi-pro interfaces too. This includes the USB sockets on your PC - the PC may have two seperate physical USB controllers (root hubs) but three or four sockets so effectively you are using a hub within your PC. So plug in an external hub into the internal hub and you have double potential trouble with timing and power and bandwidth issues etc.

I'd plug in the DAC to a USB socket associated with a unique controller within the PC (in windows, you can see the connections bewteen the usb device and the controller, so can see which is plugged into what, not sure how you do that in Linux) potentially leaving an associated USB socket empty. Use the hub and all other devices with the other controller and it's sockets.

Or get a PCI USB card instead of the hub so you get another one or two USB controllers in the machine.

PS, I'm no expert - only did do some googling and wiki reading recently

[Tim]

Hi Mark, I won't go over what Nat has said but he's outlined the issues in his post. USB can introduce many problems into the audio chain if its not tackled with some thought. The bus utilised by USB is subject to bandwidth and introducing other USB devices into the chain can restrict the bandwidth of your audio device and in the worst case cause stuttering as well as effect the SQ. All USB ports are not the same either and their audio performance can be influenced by other components in the vicinity, especially something like a switching voltage regulator. I found that just swapping ports around can make a difference, often subtle sometimes marked. Unfortunately the worst case scenario is using a hub and if its a powered hub, this can affect SQ even more as you are introducing another SMPS into the audio chain. A mouse or bluetooth device plugged into a hub or even your laptop/server ports can degrade the sound quality.

Best case scenario is to only use one USB device and if you are using a USB DAC or something like a V-Link then plugging in an external USB drive with you music library will in nearly all cases have an impact on sound quality, which is why many file based audio fans prefer a NAS. There are ways around it such as using a USB card in a PCI slot, as the PCI slot gets its own exclusive interrupt. If you then use this for audio output only to your DAC, the device gets 100% bandwidth.

Another workaround is to plug your USB DAC into the best USB port and use eSATA for you external drive if you don't wish to use a NAS. This can then be powered separately and your audio device gets exclusive use of USB. Some folk plug a long SATA to eSATA cable directly into the motherboard then trail it a metre away to their eSATA drive with a music library. This keeps the spinning mechanical drive away from the server and the serial bus.

Getting the best out of file based audio does require some consideration of how and where you attach your peripherals and also how you power them. I think a lot of these issues are never considered and is why many people think file based audio is nothing more than average - its clearly not, but you do have to think carefully about introducing other elements into the playback chain - just plugging in a number of USB devices can severely degrade the signal as you have discovered.

Not sure about your scenario as I have no experience of an OPPO for streaming, but the same principles should apply, in that less is more. I know a lot of the above does not directly answer your question, but it illustrates the problems around using USB, which should be no different in your playback chain.

[DSJR]

My computer stuff is ancient now (mid noughties), but the 7 port externally powered USB hub did sometimes seem to clog up when transferring files from one to other drive(s) connected to it. I've been lent a 2TB drive for my extended listening pleasure, but I've only used it into one of the main USB ports with no playback issues at all..

Call me ancient and old fashioned (I know, I know..), but it does seem to make sense to have an audio server set up as simply as possible, with as little hanging off it as possible - IMO at present...

[Tim]

but it does seem to make sense to have an audio server set up as simply as possible, with as little hanging off it as possible

Absolutely Dave, which I why I don't like to refer to mine as a computer - it isn't. It doesn't look like one or act like one, the only thing attached to my player is a power lead, an Ethernet cable and USB cable going to the DAC. I can no more use it as a general purpose computer than I can my Nokia phone, which is, funnily enough . . . just a phone