The speaker is very likely only powered by USB - it doesn't actually have any USB audio device inside it. It just uses the 5V power from the USB port for the little amplifier inside. You will still have to connect the audio jack to the music player or computer for the speakers to produce any sound. These cheap speakers were (and perhaps are still) popular for laptop users that wanted more sound without having to find an outlet to power a set of speakers, or replace the batteries so so often. I don't see them advertised as much anymore, especially since there are now real USB speakers that implement a USB audio device inside them. If you want to see if these have a USB device in them, and use USB for more than just power, use a USB inspector or the hardware device list on your computer. Plug them in, check it out, then unplug them and check it out. Even if there's no driver loaded, they should still show up if they have a real USB endpoint in them. Alternately, if you post the make and model perhaps someone around here can help you understand whether you can output the sound via USB. -Adam On Sat, Jul 16, 2011 at 2:30 PM, Jacopo Monegato wrote: > > Hello, > i hope the tag is correct. I was wondering about this for a while. a coup= le of years ago i bought a portable speaker, with cable and ipod dock, powe= red both via batteries and usb. I crossed my fingers and one day i linked t= he speaker with my pc. nothing. only power... but why? Unfortunately i don'= t know much about USB protocol, but since it is a serial port it shouldn't = be hard to write a software that sends the sample... or calculate the PW fo= r a "simulated" class D then send only the 1 and the zeros... am I mad o_O?= ??? because i haven't found anything yet and my old teacher told me "good l= uck if you want to learn usb by yourself, it's very hard to find technical = resources of any kind" > > Jacopo Monegato > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .