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I am connecting an NI Maschine (hardware) over USB to my Macbook Pro. Right now I'm using a USB 2.0 powered hub (by DLink or Belkin, depending). It seems fine, but these things can be hard to detect. Should the use of a hub increase latency, and if so, by how much (in millseconds, perhaps)?

This situation is pretty latency-sensitive since one of the things Maschine does is act as a drum.

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up vote 1 down vote accepted

You can use a USB 2.0 hub with a latency-sensitive device. With a proper setup, the additional latency from the hub will be less than 2 milliseconds. Just make sure you don't load the hub while you're expecting it to operate at low latency. And do not connect any USB 1.1 devices at all to it.

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Any chance you can cite this or explain why it might be 2 milliseconds as opposed to 2 microseconds or anything else? – Dan Rosenstark Jun 4 '12 at 21:29
It comes from adding the specified latencies of the various components (the incoming PHY, the hub controller, the outgoing PHY and the worst-case assumption that a large USB 2.0 isochronous transfer is in progress). In any event, 2 microseconds is less than 2 milliseconds, so that would just be a stronger statement than mine. (And, in fact, typical latency will be a few microseconds, but worst-case latency is important too.) – David Schwartz Jun 4 '12 at 21:37
Yeah, I'm going for typical here, though good to keep the WCS in mind. – Dan Rosenstark Jun 9 '12 at 17:33

Any additional length added between the device and the computer adds potential latency. Shorter, high quality USB cables are always preferred. Adding a hub will unfortunately add length.

Adding a hub also implies that you are going to add more devices onto that USB controller, which means devices competing for the limited bandwidth of that controller. Even something as unimposing as a USB mouse on the same hub can add the annoying pops, clicks, and latency that you want to avoid. Remember. The Macbook Pro you are using might have two USB ports, but chances are they are ALREADY on the same hub... just internally. So, just using both of those ports at the same time has the potential of causing issues. I know. You said everything is already going smooth.

How much latency can it add? From what I've experienced (and read in the last few minutes) no one can say for sure. There are too many factors in the mix.

In the end, if it is working, don't mess with it too much more... meaning it might be on a hub and is working, so don't use the other ports on the hub.

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the question is of scale. Might we be talking about microseconds or milliseconds? That's the question (for me). It's hard to determine whether it's really smooth since I cannot double-blind myself. – Dan Rosenstark Jun 4 '12 at 0:46

According to this thread it's microseconds:

Of course, that's without citation or measurement of any kind.

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