USB hubs reduce speed of audio interface?

[Tone Deft]

+1 to vicz and I agree with both Donnie and Fiz.

good thread.

computers are the work of the devil.

[slirak]

The OP question was whether a hub would slow down the audio interface, and it won't.

Well, that depends on what you mean with "slow down". Data transfer rates are probably unaffected or at least not affected enough to matter. But as I pointed out above, I got 2 ms added latency (as reported by Live) with both the hubs I tested (when the audio interface was connected via the hub).

It would be really interesting if those of you with your audio interface connected via a USB hub could go into Live's audio preferences and take note of the reported latency there, then connect the interface directly to a computer port, check again and then report your findings (a long with some system details, like OS version, CPU, hub brand and model and audio interface brand and model).

I have my system working, I'm just being curious. And I'd love to find a hub that doesn't add latency to my system.

[Donnie]

To put a little more technical backing to what im saying, a quick 5 min search on google provided some interesting stuff.

Some Sound on Sound input on the matter (old 2002):

As an aside here, if you are using a USB MIDI or audio interface, you should always plug it into a dedicated USB port rather than via a USB hub (powered or otherwise). Hubs multiplex the combined data from several USB devices into one data stream, so they're almost bound to introduce timing uncertainties — Griffin Technology (see July 2002 News) have introduced a USB hub optimised for audio devices for just this reason. However, if like me you now have several USB dongles, these can safely be plugged into a hub, since timing isn't an issue.

Source:

http://www.soundonsound.com/sos/Oct02/a ... an1002.asp

------

On a different site the issue of translators came up. It was stated that if a device doesnt have a translator for each port latency could be introduced. However I still want to find out more about this before reaching a solid conclusion.

Some basic info on translators:

To allow high-speed devices to operate in their fastest mode all hubs between the devices and the computer must be high speed. High-speed devices should fall back to full-speed when plugged in to a full-speed hub (or connected to an older full-speed computer port). While high-speed hubs support all device speeds, low and full-speed traffic is combined and segregated from high-speed traffic through a transaction translator. Each transaction translator segregates lower speed traffic into its own pool, essentially creating a virtual full-speed bus. Some designs use a single transaction translator, while other designs have multiple translators. Having multiple translators is only a significant benefit when connecting multiple high-bandwidth full-speed devices.[1]

It is an important consideration that in common language (and often product marketing) USB 2.0 is used as synonymous with high-speed. However, because the USB 2.0 specification, which introduced high-speed, incorporates and supersedes the USB 1.1 specification, any compliant full-speed or low-speed device is still a USB 2.0 device. Thus, not all USB 2.0 hubs operate at high-speed.

[outershpongolia]

I run my interface thru a USB port on the laptop, then 3 or 4 controllers on a USB hub, sometimes, we even plug my buddies usb hub with his 3 controllers, straight into my hub and it works fine off of one laptop.. of course both hubs are powered along with the laptop and interface but the controllers are all bus powered thru the hubs.

[vicz]

The OP question was whether a hub would slow down the audio interface, and it won't.

Well, that depends on what you mean with "slow down". Data transfer rates are probably unaffected or at least not affected enough to matter. But as I pointed out above, I got 2 ms added latency (as reported by Live) with both the hubs I tested (when the audio interface was connected via the hub).

It would be really interesting if those of you with your audio interface connected via a USB hub could go into Live's audio preferences and take note of the reported latency there, then connect the interface directly to a computer port, check again and then report your findings (a long with some system details, like OS version, CPU, hub brand and model and audio interface brand and model).

I have my system working, I'm just being curious. And I'd love to find a hub that doesn't add latency to my system.

Interesting result, maybe it is to do with the Apogee being USB 1.1. Maybe a USB 1.1 hub might cause less latency than a USB 2 forced to handle 'full speed'. I disconnected my normal f/w interface and tried the built-in interface on my M-16DX, which is USB 2. I couldn't see any difference between direct connection to my iMac or via a 7 port D-link hub shared with Novation Remote SL, Korg Micro-x, Kore 2 Controller, Maschine, KP3, iPod touch and Synchrosoft dongle. Wasn't recording anything though, just tried playing some softsynths.

[longjohns]

call me crazy, i try to have as close to zero usb devices as possible