Page 1 of 1

Re: USB cable length

Posted: Sat Jun 18, 2011 1:42 am
by ark
A USB 2 cable is supposed to be able to be as long as 5 meters (16 feet 5 inches). A USB 1 cable is supposed to be able to be as long as 3 meters (9 feet 10 inches). Launchpad might well use USB 1 electronics, so it is possible that you will encounter problems with a 16-foot cable, but I would guess it would work. It's not a matter of power.

If there's a problem, use two cables and put a hub between them.

Re: USB cable length

Posted: Sat Jun 18, 2011 2:30 am
by arachnaut
The length of the USB cable will not effect an audio delay in any way you can perceive. Your CPU latency and whether the cable is in spec will matter. These signals propagate at very high speeds, far beyond the speed of sound.

If you add long cables to your loudspeaker can you tell the difference? Audiophiles need not answer.

Re: USB cable length

Posted: Mon Jun 20, 2011 7:15 pm
by memes_33
at a certain point (probably around 16 ft.), bits of the stream could get lost and cause some problems. like you could be turning down a fader and a few points in the motion could go missing and so your on-screen fader would sort of jump down at those points. powering the launchpad might also be a problem, especially if you are using more than one of the USB ports.

Re: USB cable length

Posted: Mon Jun 20, 2011 8:02 pm
by gosinisha
there is a 5m usb repeater cable, but not for low latency devices. simply cause it works on 5V and the dropdown of voltage is so BIG...

Re: USB cable length

Posted: Mon Jun 20, 2011 9:44 pm
by Tone Deft
memes_33 wrote:at a certain point (probably around 16 ft.), bits of the stream could get lost and cause some problems.
no, you'd drop the device and on PC with Live you'd have to restart Live to get your device back. try removing/re-installing a cable as quickly as you can on a PC, just remove it a tiny bit. dropped.
powering the launchpad might also be a problem, especially if you are using more than one of the USB ports.
it wouldn't. 5V 500mA would transfer just fine.
gosinisha wrote:there is a 5m usb repeater cable, but not for low latency devices. simply cause it works on 5V and the dropdown of voltage is so BIG...
again, no.

http://www.stealth316.com/2-wire-resistance.htm
20 gauge wire, for example is ~10 milli ohms per foot. the voltage drop is well within the logic level limits (0.8V - 2V, generally speaking.)

USB length shouldn't matter past 3 meters but know that you're on the edge of what people design for. I imagine the problems occur with line reflections and near/far end terminations. 3 meters becomes a big waveguide to bounce signals around in.

Re: USB cable length

Posted: Mon Jun 20, 2011 10:25 pm
by memes_33
i stand corrected- thanks!

Re: USB cable length

Posted: Tue Jun 21, 2011 10:35 pm
by moonpie
I had problems with m-audio keyboards and 5meter usb leads. They cable would power it, but somewhere along the way, theyd lose midi connection between it and the daw (logic and ableton) It wasnt a fault of the lead, it would just stop sending midi after a couple minutes. Didnt happen with a shorter lead. I always thought 5 meters was the max for usb since they had to send and receive info within a time limit? And i figured it was possible that since i was using the max cable lenght, i would just be bordering on losing response. Hence the midi problem. Thats my experience anyways - I wouldnt buy the max lenght again anyways just to be sure. I was a major pain. Had to keep turning off and on the keyboard every few minutes. I could be wrong about the cause of course!

Re: USB cable length

Posted: Tue Jun 21, 2011 11:03 pm
by ericzang
http://www.monoprice.com/products/subde ... 03#1030312

these actually work, not sure about the powering issue though. Maybe a powered hub near the launch pad would do the trick.

Re: USB cable length

Posted: Tue Jun 21, 2011 11:28 pm
by Tone Deft
it's not a time limit thing. generally speaking electricity takes 1 nanosecond (one BILLIONTH of a second) per 6 inches. that's about 200 inches, so 100 nanoseconds of latency, not an issue for human interface or audio.

also, all this has nothing to do with midi, it's just commands sent over USB. your DAW can show the activity as midi but that's just saying that the USB signal is sending a cc#, a program change # etc. actual midi means data physically sent with an old school 33kbaud modem.

there are other issues with longer USB cables. just know that using a cable that pushes the spec can lead to wonky behavior.

http://www.usb.org are the guys that oversee all this, read there if you're curious.

Re: USB cable length

Posted: Wed Jun 22, 2011 1:37 pm
by arachnaut
I was thinking about my old college physics classes where we studied the properties of metals. If I recall correctly, metallic conductors have this sea of electrons which carry the current. Since electrons have mass they can't reach the speed of light, but they do move pretty quickly in an electric field. However, they don't follow a straight line path. The mean free path in the metal ionic lattice is pretty small, so they travel a fairly bumpy path.

Maybe I made that up, but I think not.

We ended up calculating the 'speed of electricity', but I don't remember the results.


(edited typo)

Re: USB cable length

Posted: Wed Jun 22, 2011 1:54 pm
by matthews
I curently have my Launchpad on a 25ft usb cable. I actually have a launchpad, sl25mk2, and a uc-33 all connected to one powered usb hub, and that hub uses a 25ft usb cable to get to my computer. I haven't had any issues at all. Defnitely check out a powered hub, could make the difference.