In article ,
alan_m wrote:
On 30/09/2019 15:05, Dave Plowman (News) wrote:
Have a few devices in the AV setup which are USB 5v powered. To try and
keep things as neat as possible, all the mains to that are now IEC, as
that takes up less space than 13 amp.

So decided a USB power supply would be nice. One where the PS was internal
rather than a wall wart, and a main cable I could fit an IEC plug to.
Found one on Ebay with 8 outlets - not cheap either.

One of the things it would power being the a Toslink to phono adaptor -
TV audio into the amp. Which was just fine on its supplied 13 amp wall
wart. With a USB to USB lead.

I now get a noise like a distant burglar alarm on its output with the new
PS. ;-) Changed back to the original PS, OK.

Not a ground loop either. Happens with only it plugged in.


Are all the outlets the same power rating? If not try one output that
can supply a higher current or, if possible, try your Toslink adapter on
its own in the 10 output power supply.

The device is quite a posh one, and shows on its screen how much current
each outlet is taking. But I did say I'd tried it with only the Toslink
unit plugged into it with the same result.

Does the total load of your USB devices exceed the total power available
from your USB power supply brick? For instance in may be rated for a
total of 50W which equates to 10 USB outputs at 1Amp. If you were using
all 10 outputs and a couple required, say, 2 Amps, then the other
outlets may only be able to supply 0.75 Amps or maybe when reaching
overload the regulation of the power starts failing

--
*If I agreed with you, we'd both be wrong.

Dave Plowman London SW
To e-mail, change noise into sound.