Bathroom audio

Talk about waste. Simply disconnect the transformer and wire direct to the speaker. It will be a normal nominal 8 ohm type.

Other advantage of 100 volt line is the speakers can have their level adjusted relative to one another easily. By taps on the transformer primary.

OK, I don't have copy of the regs to hand, but I believe that the regulations only apply to power distribution systems, not communications systems (there is some blurb at the beginning of the regs that defines the scope) and therefore the only thing the regs have to say is about segregation of power cables from other cables.

There are two issues here. Firstly, the "100V" in a 100V line system is a theoretical nominal value, not a low-impedance 100V rms continuous signal. In practice, you are only ever going to see momentary peaks of this voltage and the lines are high-impedance to reduce I2R losses. So, from both a practical and a common sense basis, the safety risk (of getting a shock off an audio signal in this context) is minimal to negligible.

Secondly, like it or not, 100V line audio systems are ubiquitous in leisure facilities (changing rooms/showers, swimming pools, etc.) The main consideration (besides of course getting adequate coverage) is that the speaker is proof against the environmental conditions. (Chlorine from swimming pools is particularly corrosive, as is salt spray in a marine environment). This means that you tend not to put speakers in the steamy/splash zones anyway if at all possible. If you do, then you would normally go for IP6X protected units, so the likelihood of a shock (even from a high-power PA system) is negligible.

The idea that the audio signal is a hazardous voltage is not a design consideration. This may have changed with the 17th edition, so I may be out of date...

Dave Osborne coughed up some electrons that declared:

As I said, one could argue it both ways - and that is an equally excellent argument.

Cheers

Tim

Don't think 100 volt line is considered hazardous - looking at the type of connectors used.

Dave Plowman (News) coughed up some electrons that declared:

OK - how can one justify that though? I realise that "100V" might be peak (or is it "peak to peak"), not RMS - but even so, there must be a decent bit of current available to drive a medium wattage speaker when sustained loud music is playing?

The reason I quoted the regs is as a demonstration that even normal SELV isn't acceptable in Zone 1 (or 0) - the allowed voltage is further reduced

Just because the electrons are dancing to R&B doesn't mean they can't kill you ;->

Cheers

Tim

Thing is it's not really used in the home so domestic regs are unlikely to apply. And no one in their right mind would use it for playing loud music. Pop concert PA rigs gave up on it many moons ago.

well just don't wire up a guitar speaker when the artiste decides to whack a power chord through it. You can get a helluva a belt off em! And that's only about 50v RMS..

It can be. It can be as lethal as 110v AC IF you e.g. get a full power 'hum' on it. AND you are across the terminals so to speak.

well I agree. If that's the aim of the game.

But you might decide that it was a good idea to pump 100v stuff all over the house and garden..

Don't get hum, then. That would be a fault condition. And unpleasant to listen to so you'd turn it off before investigating.

Main problem with 100 volt line is the speakers are usually of poor quality. And can often benefit from some careful EQ. But only if they are all identical. For domestic use it's far better to distribute at line level and have a local amp for each speaker(s). Thus allowing things like level and EQ to be easily set to suit the conditions.

Its often whilst investigating that it happens ;-)

If you investigated a faulty IP rated light fitting in a bathroom with the power on that could kill you too...

Indeed. But that is precisely why the same precautions should apply.

As it does with a mains outlet for a shaver? If you fiddle with that it could kill you easily.

Dave Plowman (News) coughed up some electrons that declared:

Dave,

You cannot have a shaver socket (or any mains equipment, with a few very specific exceptions) in Zones 0 or 1.

I didn't say that you shouldn't have a 100V PA system in Zone 2 - just drawing attention to the OP before he decided to stick a loudspeaker over the bath :)

Cheers

Tim

The OP wasn't going to use 100 volt line anyway.

Dave Plowman (News) coughed up some electrons that declared:

Re-reading it, yes you're right.

Why are we arguing then?

;-O