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I know that normally usb 2.0 limit is 5m, but is there any difference how I use that cable? Can I simply extend cable longer than 5m if no data or audio transfer is required, just want to feed really small usb speakers?

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    Depends on the port you use and quality of cable. With right components connections over 30m is entirely possible ( and done in real life applications ) Feb 3 '16 at 14:09
  • There is no ports(if you mean PC), just a 5v power supply with USB output for charging smartphones, tablets and other devices. And I don't want to use extra components(if you mean hubs, active cables). I want simply extend ~10m long cable that carries electricity only. Is it possible?
    – Zuu
    Feb 3 '16 at 14:27
  • On wikipedia you can read "The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost". The first it is a problem of comunication. But, more long is the cable more electrical resistance it will do, more power you will dissipate (there is a max output you can give from each device), more the ending voltage will decrease... if you go below 4.45V you should start to experience problems. It depends from the port you use and quality of cable.
    – Hastur
    Feb 3 '16 at 14:30
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Consider a different solution: install an USB power adapter close to the speakers and use it to supply the power to the speakers. :-)
Image from wikipedia .

Usb Power Adapter


Q1: Is there any difference how I use that cable?
A1 (Short): Yes, there are problems of communication over the 5mt [1],[2] (see below), and of maximum power deliverable. (The longer or thinner the cable, the lesser the final Voltage [3],[4]).
For example some HDD drives need good cables (short or with a good section of the copper cable) in order to work properly, because their absorption is close to the limit of the port.

Q2: Can I simply extend cable longer than 5m if no data or audio transfer is required?
A2: (Short): It depends.
If you use only to "deliver power" it could work if it is not involved the communication aspects.
Note that if the Voltage is too low for example the battery circuit of a mobile can work not properly.
(Nowadays many battery, for example, decide if they are charged checking their temperature that depends from the amperage and voltage with which they are charged: this can change their life expectancy. Moreover they can decide that the voltage is too low to have a proper charging cycle and don't start at all, or even worst to continue to switch between the charging status and the not enough to charge status)..

Q2B ...I just want to feed really small usb speakers...
A2B: It depends, again. If the audio arrives through a different cable, you should only experience a lower final volume and some distortion.

Note that with new compliant cables (USB Power Delivery, "PD") and devices some limits are overcame. Again you can read more about on the usb site[5] and on wikipedia [6].


Some words more

From Wikipedia [1] you can read

USB 2.0 (standard) provides for a maximum cable length of 5 meters for devices running at Hi Speed (480 Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost. When adding USB device response time...

From the Cables and Long-Haul Solutions of the usb faq on the usb.org site [2] you can read

  1. I want to build a cable longer than 5 meters, why won't this work?

A2: Even if you violated the specifications, it literally wouldn't get you very far. Assuming worst-case delay times, a full speed device at the bottom of 5 hubs and cables has a timeout margin of 280ps. Reducing this margin to 0ps would only give you an extra 5cm, which is hardly worth the trouble.

  1. I really need to put a USB device more than 30 meters away from my PC. What should I do?

A4: Build a USB bridge that acts as a USB device on one side and has a USB host controller at the other end. Use a long-haul signaling protocol like Ethernet or RS-485 in the middle...

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  • Installing adapter closer to speaker is something I want to avoid. Distortion is not problem, because the sound is lofi by default, thought volume level is important. I think it's worth to try at least. Thanks.
    – Zuu
    Feb 4 '16 at 3:10

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