Intelligent Power Strip

I'd guess some kind of coupling / earth loop. eg if the power strip switches the live but not the neutral, there could be a parasitic/induced current on the neutral side that's somehow leaking through into the speakers. You'd need much less than would trip an RCD.

As an aside, these are quite handy as power takeoff devices for power tools, eg to control a dust extraction vacuum:

Theo

When you power the speakers, do you hear a relay click on? Maybe they act as unpowered speakers when not powered, and are picking up stray signals like that?

What if you test by powering the speakers from a different socket?

What if you unplug the speakers from the power strip altogether?

Have you tried plugging the speakers directly into the wall socket- with as much of the other set up 'as is'?

My 'guess' is, like most people, you have 'no shortage' of mains leads under your desk and you are getting stray, radiated, pick up rather than something from resulting from being plugged into the 'smart' socket.

While the test I suggest isn't 100% sure to clear the smart strip (if it is radiating something it could still get into a nearby device, it it does clear the problem, you can be near enough certain it is the culptits.

Make and model number of sound system ?

Paul

My thought is the power strip electronics have seen better days. Everything is made to stop working correctly.

If you do FMEA analysis of the power strip, there are two areas of interest:

2) On a power switching power strip, the power relay is a component which can fail. If the relay is a cheaper one, the contacts may weld under load and then the strip cannot turn off the power. The relay has to be small enough to fit into the strip, which means even if your intentions were honourable, you could not put a 4X rated relay in the unit, as it would not fit. In box-shaped power strips, there is more room for a quality relay. The form factor plays a part in what the consumer can expect.

The thing that drives the relay coil, that circuit can be pretty sloppy. It's possible the engineer designing it, did not take the design seriously, and only spent one morning working on it. You might notice on some power strips, the threshold drifts with age, and that just means the engineer didn't understand the circuit all that well.

On an ATX powered PC, the Watts can be 1 watt when it is off, yet the VA can be 7 watts, and it is the VA which is easiest for the engineer to measure inside the power strip. It could be, that the circuit is working perfectly fine, and it is your mis-understanding of the circuit draw, that is causing the functional failure. Like, say the monitored PC, has an iPhone plugged in and charging. Now, the power strip will not turn off the peripheral mains outlets, because the "soft-off" power is too high.

Paul

My desk is a long narrow oak worktop. Supporting it are two units built with my tender hands. The left hand one is containing eight pull out drawers on runners. Above that is a Fujitsu cut-sheet scanner circa 2010. It can be driven by xsane but it is better from Windows XP, retained as a virtual machine mainl;y for that purpose.

The right hand one is just a box that holds two mid-tower computers. Tucked in behind them are three power strips and an ethernet switch. Above that is a Brother colour laser printer.

What with the panasonic mobile phone, Their are cables galore.

I have just completed identifying which mains plug is which with a black and a white marker. In the process it became clear that the intelligent power strip has dimenture. It would be a hassle replacing it. I shall turn off everything I can reach every night.

Thank you for all the suggestions.

Regards, Alan

When the PC is soft-off, you should measure W, VA, PF at the mains plug of the monitored PC.

Compare the measured VA, to the threshold value listed for the power strip monitor. Some have a knob for adjusting the sensitivity, meaning the threshold is variable.

Paul

I would but I would have to be a contortionist.

Alan

This is why my equipment is on tables.

None of the PCs are on the floor.

I store my "dust bunnies" at floor level.

But this also means, I have to lift the latest PC pretty high, to put it on its perch. The drive bays in the new PC, end up at roughly the same height as my head.

Paul

Paul snipped-for-privacy@needed.invalid wrote

I compute from a deep armchair with my feet up with a stiff thick stiff cutting board on my lap for the mouse and keyboard goes on that when its being used so no contortion required when changing hard drives in that sort of drive bay or with CDs/DVDs

All of mine are