cyrano.mac wrote:Sorry, Hugh, it's not extremely unlikely to have a bad ground.
I can't agree. In well over thirty years of working with mains installations in the UK I've only come across a handful -- certainly less than a dozen -- of occasions where I've discovered problems with mains grounding in building wiring. I'd count that as pretty rare. Obviously YMMV... (Sadly, the same isn't true in some of the far-flung corners of the world where I've worked. Some Malaysian mains wiring still sends shivers down my spine... :shock: )
However, when I'm working out and about I do always carry a tester and I always test sockets (and their ground impedance) before I use them because any safety earth problem is potentially a very serious one.
Unfortunately, the UK doesn't even bother to keep stats about electrocution.
Er... completely untrue. The Health and Safety Executive collect and publish records of all work-related injuries and fatalities, and their causes.https://www.hse.gov.uk/statistics/causinj/kinds-of-accident.pdf
This 18/19 report states that 4% of 147 fatalities were caused by contact with electricity.https://www.hse.gov.uk/statistics/pdf/fatalinjuries.pdf
And this one states there were 9 recorded fatalities due to electricity in UK workplaces in 2019.
The UK's Office of National Statistics also publishes data on all manner of things, including recorded deaths related to electricity, with data breakdowns on location (ie. home, residential places, industry, farms and so on). The figures for fatal electrocutions in England from 2001 to 2016 provide a total of 332... in 15 years. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/deaths/adhocs/007964deathsfromexposuretoelectriccurrentbysexandagegroupengland2001to2016
An older (1998) generic HSE report states: "Each year about 1000 accidents at work involving electric shock or burns are reported to the Health and Safety Executive (HSE). Around 30 of these are fatal. Most of these fatalities arise from contact with overhead or underground power cables...."http://www.esldatasheets.com/Documents/HSE/ESaY_HSEPub_indg231.pdf
Although these figures are only for England, it's clear that fatal electrocutions is in the low tens, each year, at worst -- and that's tragic, obviously, especially as they are avoidable. But I find it hard to believe there were millions more in Scotland and Wales... so I don't know where your extraordinary figure of 2.8 million came from. It's simply not credible!
Our local regulations are among the most severe, but don't protect from sheer stupidity.
None ever could... as I said, education is the only way forward. Which is why I find it so sad that so many young people consider eschew science and technology these days.
By bridging audio and mains ground you are creating the environment in which these kind of accidents occur.
Er… no. That's utter nonsense... There certainly are situations where ground bonding needs careful consideration, most notably when working with non-standard mains supplies or equipment powered from isolating transformers... but these are not relevant in the hum-seeking context being discussed above.
You are exposing double insulated equipment to grounded equipment through the shield connection...
And what exactly do you think happens when you plug your double-insulated keyboard, or laptop, say, into a Class 1 stage-amp, or a class-1 mixing console, or a class-1 active speaker… ?
Class-1 devices almost always have the audio reference ground tied directly to the star earthing point along with the chassis and mains safety earth. Indeed, this configuration is strongly recommended as the 'best practice' for equipment grounding by the AES, no less.
Check out the diagram on page 5 of the AES48 documention, for example: http://www.aes.org/standards/comments/drafts/aes48-xxxx-190121-cfc.pdf
(Sorry this is a draft version... the final document isn't publically accessible on the AES website, but the diagrams and recommendations are the same).
And the only
reason some class-1 devices have a 'ground lift' switch with your beloved RC network is to avoid ground-loops when there are multiple interconnected class-1 devices.
All the 'grounding plug' is doing is replacing that tie to a real ground (that would normally be provided by a Class-1 device) in systems which comprise all double-insulated equipment and thus lack a solid ground reference.
I can assure you that I take mains safety extremely seriously -- both personally and in my role as Technical Editor of SOS -- and I certainly wouldn't suggest any practice that represented any potential risk. Bonding the audio reference ground of a double-insulated device to mains earth carries no risk whatsoever with normal working equipment, and nor does increase risks or affect the functionality of any conventional safety devices under fault conditions.