60 hertz hum

It's an old expression and I was trying to be polite as a visitor to a non UK newsgroup.

Otherwise I'd have said bollocks or s**te. ;-)

--
*No sentence fragments *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

FWIW, I've heard crikey used in the U.S. many times (but I don't recall hearing it in the U.K. during the year +/- I lived there). Perhaps it's a regional thing.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam.  Our true address is of the form che...@prodigy.net.

I knew that would raise some rabble. Yes, of course I recognize the potential (so to speak) problems with opening the safety ground connection. However, a few interesting points exist in this particular situation:

- The device is a laptop, and there is no direct connection from the ground pin through the (double-insulated) AC adapter/charger to the laptop chassis, so it's really not much of a "safety" ground.

- There are two small value (10 nF) caps from each side of the power line to the ground terminal inside the adapter, presumably as an RFI suppression measure.

- All of the audio equipment involved was plugged into the *same* outlet strip - it seems highly unlikely that there'd be much of ground loop within the 6" or so of 16 gauge wire separating the plugs

- Finally (and this is really no excuse), my house is old enough that I'm not convinced that all of the three prong outlets have their ground pin connected to anything at all. It's not so old that it's knob-and-tube, but the outlets were originally two prong, and I think that many were just replaced with three-prong as placebos, without pulling a ground wire. At least the garage (with the concrete floor and the power tools) is wired correctly...

-- Mark "I prefer heaven for climate, hell for company."

Hi...

As a side issue, there are testers available for only a couple of dollars that you can plug into your outlets that will (by way of three neon lamps) easily tell you whether or not ground exists, and if hot/neutral are reversed.

Just mentioned it wondering if it might not increase your comfort level.

Ken

How do you work that out?

Alan

You obviously haven't lived!(:-)

Used to be an everyday exclamation

Alan

dunno about there in in Australia and New Zealand it's heard occasionally.

my (aging) Concise Oxoford dictionary dosen't specifty that it's unique to any place.

Bye. Jasen

Second harmonic of 50 Hz. A lot of the hum you hear in the US is actually

120 Hz for the same reason. Most objects, including speakers, really don't radiate that well at 50 - 60 Hz fundamental, but can and do radiate pretty well at some of the higher harmonics.

I always thought the 60Hz caused core laminations, coil windings, etc to smack into each other at both peaks of the waveform, hence the 120Hz sound from a 60Hz source. I could be off on the process, but I do know that if I use a sound editor on my computer to produce a 120Hz sine wave it sounds just like the 60Hz hum from transformers.

Yeah, I think a magnet or buzzer (like in an old alarm clock) will be attracted by both peaks of a 50 or 60 Hz input, and oscillate at the second harmonic.

I had a similar problem that was solved by using Radio Shacks Audio System Ground Loop Isolator P/N 270-054.