How Long Is A USB Cable?

[Glenn D]

Seriously ...
If I were to use a keyboard with a USB only midi and power connection combined (eg a Alesis V61 or Nektar GX61) on stage, how long an USB cable can I use to reach an off stage computer?
I understand 5 metres is probably the practical limitation for midi transmission but does the fact that the cable carries power as well make any difference?
Thanks, Glenn
PS: Any one have preferences between the Alesis and the baby Nektar for touch, and especially evenness of velocity response with Pianoteq?

[radian]

It's 3 metres long.

https://en.wikipedia.org/wiki/USB#Cabling

If you want to to go further I guess you can with a hub?

[MarkPAman]

I've had a webcam on 10m or maybe even more, though for that use I wasn't too fussed if it had problems - though it didn't.

I was trying to find out what animal was digging small holes in my garden.

[ef37a]

I doubt there would be any noticeable power loss even at 10m unless you went for THE cheapest, flimsiest cable you could find.

Does the keyboard not have a power input? You can in any case buy USB power "injector" cables, use one with a 5V 1A wall rat.

I have run 5m no bother, if you need to go further you can get an "active" USB extender cable. 4.5m and then tack on another 3 or so.

Dave.

[ConcertinaChap]

I've used active USB extender cables and they're very effective at extending USB 2 cables beyond the 5 metre legal limit (I've not tried USB 3 extenders). However they do consume power to do this (hence the "active") so there will be less available at the far end.

CC

[Folderol]

I don't know, but are 'proper' USB cables supposed to be transmission lines?
If so, the length limit would be determined simply by signal/noise ratio and receiver sensitivity...
Well, I guess that's a can of worms in itself

[ef37a]

I don't know, but are 'proper' USB cables supposed to be transmission lines?
If so, the length limit would be determined simply by signal/noise ratio and receiver sensitivity...
Well, I guess that's a can of worms in itself

Well, any cable can be considered a transmission line? But think on Will, 'prop...I mean ANALOGUE TV just got grainier and grainier as the signal level dropped. Digital starts to get "blocky" then blanks altogether. I would guess there is a sharp cutoff length for any given system?

Dave.

[Glenn D]

Thanks for the replies folks.

Neither the Alesis or the Nektar have the option of mains supply. So it seems that an active usb hub as suggested by ConcertinaChap is the way to go. Plus some practical experimentation with exactly how long is reliable.

By way of context - I'm looking for a 'slim' and light keyboard that I can fit into a dummy clavichord/virginal Tudor styled case to use in my touring show. Many of the Dowland songs and Purcell arias have EDM/Urban/Jazz/etc backings played from my computer but I want to play at least a couple of songs freehand. My usual keyboard, a Kawai MP8, has a super lovely touch but realistically I can only consider using it when I am near home. When travelling interstate or overseas it's way too heavy! A Roland RD64 would be the perfect alternative but it's far too expensive for me at the moment.

Nga mihi,
Glenn

[ef37a]

This https://linitx.com/product/mikrotik-5v- ... gKF0vD_BwE

Will inject power at the keyboard end if needed and the active extender goes at the laptop end. How far do you think you need to go? You can get USB -CAT X -USB converters that will go 90mtrs but they are pricey.

Dave.

[CS70]

I don't know, but are 'proper' USB cables supposed to be transmission lines?
If so, the length limit would be determined simply by signal/noise ratio and receiver sensitivity...
Well, I guess that's a can of worms in itself

Well, any cable can be considered a transmission line? But think on Will, 'prop...I mean ANALOGUE TV just got grainier and grainier as the signal level dropped. Digital starts to get "blocky" then blanks altogether. I would guess there is a sharp cutoff length for any given system?

Dave.

A digital signal has most often a degree of error correction, with some encodings being very sophisticated in their capabilities, hence the blocks - information degrades differently

But ultimately there's an A/D converter someplace, which looks at a voltage over a small bit of time and decides if it's a zero or a one... if it's all low, it will be all zeros and suddenly you'll find yourself walking alone in restless dreams, turning your collar to the cold and damp and listening to the sound of ..

[forumuser932794]

As a computer engineer and hobbyist musician, I'd offer ...

Generally, the length should be 10 meters (say 25'), but it depends on the quality of the cable and the signal that is being carried. You just have to try some combinations. I also agree with the comment that a powered hub might help.

USB wasn't intended for long distances.

After some trials I did get my 4x4 MIDI controller pad USB to talk with my MacBook pro and Komplete. It took a few combinations to find one that worked.

Hope this helps

[Dr R]

But ultimately there's an A/D converter someplace, which looks at a voltage over a small bit of time and decides if it's a zero or a one... if it's all low, it will be all zeros and suddenly you'll find yourself walking alone in restless dreams, turning your collar to the cold and damp and listening to the sound of ..

Ultravox, "Vienna"

[CS70]

Sounds about rght!

[ef37a]

Not sure what good a hub will be? Yes it will ensure full 5V at full 500mA supply power is available but I don't think power is going to be a problem? I think it is data corruption that ultimately limits cable length.

Still, we most of us have a couple of old hubs kicking around? Worth a do!

Ooo! http://cpc.farnell.com/pro-signal/usb-b ... gIRNPD_BwE

Not nearly as expensive as I thought. Might grab a set and have a play.

Actually that looks bloody perfect! 480mbs and comes with a power supply.

Dave.

[Drew Stephenson]

Ooo! http://cpc.farnell.com/pro-signal/usb-b ... gIRNPD_BwE

Not nearly as expensive as I thought. Might grab a set and have a play.

Says USB 1.1 compliant only Dave - don't know if that affects your thinking?

[ef37a]

Ooo! http://cpc.farnell.com/pro-signal/usb-b ... gIRNPD_BwE

Not nearly as expensive as I thought. Might grab a set and have a play.

Says USB 1.1 compliant only Dave - don't know if that affects your thinking?

Think that means backwards compliant? http://www.farnell.com/datasheets/1812889.pdf

Dave.

[Drew Stephenson]

Looks like a different product? Just on my phone at the moment so struggling a bit but i couldn't see anything on the first link that specified usb2