In sci.electronics.repair, on Mon, 25 Sep 2017 08:34:43 +1000, Trevor
Wilson wrote:

On 24/09/2017 12:59 PM, micky wrote:
People on Amazon ask some of the stupidest questions (he said, as he's
about to ask one).

I"m looking at a panel-mount extension cord for a car radio with USB and
3.5mm inputs, and someone asks "could i use this to connect a usb
headset to the 3.5mm headphone jack on my tv?"

**No.


And all the answers related to the fact that it uses two unconnected
cables, and about converting from one jack to another, and I thought the
problem was deeper than that, that there is no way to make an adapter
from the audio output of a 3.5mm jack to a USB headset, because, well,
it's USB! It's uses some sort of fancy USB signal, like all the other
USB devices do. It doesn't have L+, R+ and ground, like earphones with
round plugs on the end have. OR does it?

**No, it doesn't. USB (Universal Serial Bus) is a digital connection
system. Any audio signal present is in a digital form and must be
converted to analogue, before it can be heard.

It took a while for this to sink in but I think you're right. Maybe the
adapter has some converter. It's coming from China and it's made it to
California and will arrive in a week, and I'll know then. ;-)

Otherwise, I think I can convert the mp3's to .cda's though I haven't
found a converter yet that will do a whole directory, not just one at a
time.

..cda's are iirc 4 times as big as .mp3's but flash drives are so big now
the only problem is the time it takes to convert things.

BTW, I use little powered Logitech USB speakers with my laptop and they
get their power from the USB, and they work very well. If I'm wrong
above, does the power piggyback on one of the 3 wires or does it use the
fourth wire?

**Part of the USB convention is that a small amount of DC power can be
transferred to devices that require it.