Shielding a passive audio switchbox

But not so much perhaps thrown together live outdoor concerts.

Fact is that there were and still are a LOT of "temporary" drops in place on an outdoor event stage. Those may or may not be wired properly and may or may not be inspected to be complaint with said stated wiring configurations. Fact is there was a lot of fudging taking place.

Even in the home. Look at all the outdoor Christmas decoration 'accidents'.

One can STILL go buy a "pigtail" cheating device for a line cord to this day.

Your mother was one of them.

(just saw your next post... you deserve that) (she deserves a kick in the head)

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** No - it is all fact you ignorant jerk.

** Stupid and irrelevant.

New construction rules take decades to become common place, the old two pin plugs were and are compatible with both outlets too.

Fender guitar amps ( and many other brands) were sold *new* with two pin plugs in the late 60s and early 70s.

** Do tell.

..... Phil

You're learning from AlwaysWrong, Phyllis.

No, it's certa "3 pin domestic outlets and plug strips were scarce"

Which is *false*. They were common in the late '50s and standard by the '70s.

Irrelevant.

AlwaysWrong is illiterate, too. Who could have guessed.

It's universally known that AlwaysWrong, is *ALWAYS* wrong.

No... I know what I said... show ya in a sec...

Kick in the head... even if it is a rotted corpse.

So much for your claim of illiteracy. Nice try though, ya piece of shit.

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** Having no safety earth on their amplifiers was standard then. ** Got nothing to do with the *vast majority* of pre-existing premises.

** No it is TRUE !!

Scarce = not abundant, insufficient - you illiterate CRETIN !

** Completely relevant to the FACT that very few guitar amps in use in the USA in the 1960s had 3 pin plug with safety earth.

You have no idea either way at all.

Fuck off.

.... Phil

Of course you do. But, because you're illiterate, no one else can have a clue.

AlwaysWrong is *always* wrong, to the surprise of not a one here.

'60s"

Hate to say it but this time you are wrong. Yes it became code later but be fore then it was not common. I've worked on too many houses not to know. Th e old ones with knob and tube are too old but there are a hell of alot of t hem with 12-2 Romex without ground after that.

HA, been cleaning the basement and garage because it is not organized and a lmost looked like the TV show Hoarders. I found a bunch of those 3 to 2 pro ng adapters. I decided to plug them all together and now it is about a foot long !

But I don't know where you are, here it seems they always got away as cheap ly as possible.

That's completely irrelevant to what I said, Phyllis.

Completely false !!! (see your exclamation point and raise one)

Not at all "scarce". *STANDARD* ya dope! By the '70s hey were DOMINANT. Hardly "scarce".

You're just like Slowman. A dumb Aussie who thinks he knows more about the US than someone who's lived in the US all his life. IOW, a flamin' idiot.

Sure, Slowman.

You misspelled "Phyllis".

NO, you're wrong. It was common in new construction well before 1970 and code *long* before 1980. There was no knob and tube construction in the '50s, much less the '70s.

BTW, "12-2" refers to the conductors. The standard for outlet wiring today is 12-2.

Sure we had them, too, even though every outlet in the house was NEMA

5-15R. We still had ungrounded extension cords (still do, in fact).

Planet Earth. Where are you?

What is this fuss about the ground (lift) switch ?

The "shock" you got is most likely due to the mains filter Y-capacitors. The same thing happens when you plug in a desk top computer into an ungrounded 230 V socket. The computer chassis will float at about 115Vac, but is harmless for humans but may burn sound cards etc. if plugged in while the mains plug is in the socket.

The mains transformers in old tube amplifiers had a quite high capacitance between primary and secondary. Especially if a center tapped anode winding was used, the capacitive leakage current went directly into the chassis.

Of course the "shock" might be pretty nasty if it went into microphone case and you touched the microphone with your lips :-).

To understand the need for a ground lift switch, one should consider the TN-C_S mains wiring convention used before in many countries. In addition to the Live wire, there was a common PEN wire from the distribution panel to each socket. In each grounded socket the PEN conductor was split to the PE (protective Earth) and N (Neutral). The device cord had L, N and PE, so whatever way the plug was inserted,the device chassis was connected to the fixed house PEN wiring.

The problem is that even during normal operation, the load neutral current flows through the PEN wire, causing a voltage drop. With different loads connected to different mains sockets, the PE pin voltage is different. Connecting two audio devices together, part of the higher load current device neutral current will flow through the audio cable shields, causing all kinds of hum problems, Disconnecting the device chassis from the PE with a ground (lift) switch will eliminate this current.

In countries using CEE 7/4 plugs

(large parts of Europe) simply put some tape over the plug PE connectors, before plugging it into a grounded socket, will disconnect the PE without the need for a grounding switch :-).

Current regulations require TN-S wiring,i. e. a separate PE and N connector from the building distribution panel to each socket. Thus no current (and hence no voltage drop) will occur in the PE wiring in normal operation, hence the potential difference between two device chassis is practically zero and much less need for a ground (lifting) switch.

Arguably a valid response if that is your opinion.

This last part, however... bad news.

Your claim to being an adult must be completely irrelevant to actual mature behavior.

A dumb jerk like you must have gone to one of Trump's "universities".

And folks jump on the folks who throw it back in your face.

As usual, everything you say is irrelevant and as *always*, wrong.

d code *long* before 1980. There was no knob and tube construction in the '50s, much less the '70s. "

Not here. This is Cleveland and suburbs. I have plenty of experience doing that type of work in this area so I KNOW. Of course in many places local co des supersede the NEC, which may or may not be that case. "Planet Earth" is not quite zeroed in enough. But I have done everything about wiring except one thing, which is to wire up one of those generators and I am not going to. If you do it wrong you can electrocute a lineman, it has happened when someone didn't hook one up right and their generator was backfeeding into t he mains. Couldn't have been too densely populated of an area for obvious r easons.

mature behavior. "

Look who's talking here. You jump into name calling as soon as someone disa grees with you, and I figured out our problem. What is a transformer you ar e not calling a transformer. ANYTHNG that transfers electrical energy throu gh a magnetic field it a transformer. If the windings are common or connect ed together internally it is an autotransformer.

that coil with secondaries in a switched mode power supply IS a transformer , as are RF transformers, interstage coupling transformers, control transfo rmers including those with a saturable core like the pincushion transformer in an old color TV. Just because they don't run off the 60 Hz mains doesn' t mean they are not a transformer.

If this is not the case then the ball is in your court and you acted the fo ol and cannot explain your position in this. Which is it ?

And BTW, I not immature and don't shoot people in anger, however if you wer e to come at me with a big knife attempting to decapitate me you would make a good sieve. Speaking of balls, my fighting days are over, but I remember what it was like to be young and dumb and full of cum.

That coil with the isolated secondary windings in an SMPS is a transformer, yes or no ?

Nope. I call folks name who have insulted me in that thread or previously. Dipshits like you notice only the elements to make a case for you keeping your mouth out of it.

Oh... that's right... you are one of the retarded f*ck culprits.

Learn to read. I never said anything about coming at you.

I say electrostatic, or as your better description fits. On an opamp I switch from coil sensor for EMF, to a short antenna stub for electric. In EMF mode, a shield or Faraday cage has little to no effect at low frequency AC.

Greg