Why amplifier does not typically have ground component in the power chord

Yes

all my equipment have 2-wire plugs.
but i noticed that my phillips 212 TT had a ground wire coming out of it, and the rear of my Yamaha receiver has a screw with a ground symbol on it.
i have those 2 connected together...is that right ?

That is absolutely how it goes..
 
Here is how it works for 2 prong devices.

Power cord is connected to a primary coil of internal transformer. It ends there.
All internals including chassis are wired with a transformer secondary . There is no direct electrical connection between primary and secondary.
Some point of the secondary is deemed 0V by designers and is connected to chassis.
Outlet neutral and ground are connected together at the main electrical panel of your house.

If you try to connect chassis to ground you are in fact connecting one side of primary to some point of a secondary.
Results may vary.:nono:

On a side note older outlets and power cords are not even polarized.
You can plug them either way. It doesnt matter which side of transformer primary is hot.
 
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Here is how it works for 2 prong devices.

If you try to connect chassis to ground you are in fact connecting one side of primary to some point of a secondary.
Results may vary.:nono:

Would one of those varying results include the AM Tube Radio in post 11 that "Flamed" as soon as I turned it on? I have an Audio Design PA100 Power Amp that the speakers (-) terminals are attached to the chasis. I'm guessing it wouldn't be a good Idea to ground it either.
 
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Would one of those varying results include the AM Tube Radio in post 11 that "Flamed" as soon as I turned it on? I have an Audio Design PA100 Power Amp that the speakers (-) terminals are attached to the chasis. I'm guessing it wouldn't be a good Idea to ground it either.

Results vary from "nothing happened" to "total meltdown" depending on design.
Your amp appears to be of a second variety.
 
Would one of those varying results include the AM Tube Radio in post 11 that "Flamed" as soon as I turned it on? I have an Audio Design PA100 Power Amp that the speakers (-) terminals are attached to the chasis. I'm guessing it wouldn't be a good Idea to ground it either.

I don't usually post on old threads, but I feel this is relevant for anyone stumbling on this safety issue.

The above mentioned mentioned AM Tube Radio that self destructed may well have been of the transformer-less variety with a non polarized plug. In which case connecting the chassis ground to house ground may have shorted all manner of things.
aAc_NuclearExp.gif
 
Interesting to note that nearly every guitar amplifier I've ever owned (Marshall, MosValve, etc) has been a two prong...

I have two Traynors, both from the '60s, and they were both wired to original spec with two-prong cords. Used to shock me constantly. I rewired them both with solid ground connection to chassis and a three prong cord, eliminating the "ground" switch along with all dangerous voltages w.r.t. ground on exposed surfaces. No more shocks.

Cheers,

Otto
 
PC's and laptops use three prong. But most mini's and ereaders use two.

I've seen a lot of full-size laptops with two-prong power supplies.

Some new POWER amps may have 3 prong but again, up to the manufacturer and remember, 3 prong grounded outlets have been around for decades.

I have an early 70s preamp with a three-prong cord and three-prong courtesy outlets on the back. Although I've seen pictures of the exact same preamp with two-prong courtesy outlets.
 
Interestingly my Yamaha M2 (1979-80) is a consumer amp and only has a 2-prong cord. My Yamaha P2201s (1976) are pro amps and both have 3-prong cords, despite being older than the M2.
 
First, you need to understand how the 3 wire grounded circuit works. The hot side (120 volt potential, and yes the narrow blade of the polarized plug) delivers the current. It is usually fused the minute it enters a piece of equipment and then goes to a power switch, then to a transformer. All stereo equipment works on DC voltages, so that is why there is a transformer. The neutral is connected to the ground in your electrical circuit breaker box and is used to complete the 120 volt circuit. The circuit breaker box has 2 120 volt circuit in it. When you connect the 2 120 volt circuits in series, you get 240 volt, which is used to run your electric clothes dryer or kitchen stove, which requires high amount of current to operate. The third wire, the ground also goes to the circuit breaker box and then goes outside to a very long copper ground rod that is pounded into the ground outside of your house. The size of your electrical service is determined by 1) the gauge of wire to your house from the electrical company, and 2) the size of your mains breaker.

2 prong wiring to lots of equipment, simply is all that is required. The is little to no risk of electrical shock, under normal, expected operating conditions. As an example, a vacuum cleaner does not have a ground wire. It's usually used on carpet, which is an insulator, and the vacuum is usually made out of plastic so there literally is no way to complete a circuit, and get electrocuted.

Toasters are 2 prong, and usually made of metal, but they are used in the kitchen where GFCIs are required. GFCIs monitor current from hot to neutral, and if they are not equal, the GFCI trips, cutting all power to the outlet.

Now, most hifi equipment is made of metal, but you as the user are expected to operate it within the home, not on wet concrete floors, or use said equipment with frayed power cords. They are safe as long as you abide by these simple rules. When you decide to take your receiver outside in the rain, that trouble can certainly come about.

Three wire cords for amps certainly are now popular, as are IEC sockets. But actually, all of these amps could have gotten a UL listing with just a 2 prong plug. The manufacturers that promote the 3 prong are using it as a marketing tool.

Also, the three prong plug can lead to ground loops for hifi equipment. If each component has it's own ground and if there is even the smallest milliamp leak of current to ground it will create hum.

Wayner
 
A whole lot of confusion comes from the use of the term(s) "ground" and "earth" when used

in conjunction with electrical circuitry. The words "ground" and "earth" are what their

definitions connote. Problem is that from place to place and from application to

application, there may be a measurable difference of potential (measured in volts) between

one "ground"/"earth" point and another. To further complicate the matter, these terms have

also been applied to the most electrically neutral points on individual pieces of

equipment.

What this means, in effect, is that there may be significant differences of potential

between the neutral points in the overall circuitry of the setup, including everything from

the stepdown transformer feeding the power to house to the internal circuits in the

equipment.

Basically, change "grounding" circuitry at your own risk!
 
Would one of those varying results include the AM Tube Radio in post 11 that "Flamed" as soon as I turned it on? I have an Audio Design PA100 Power Amp that the speakers (-) terminals are attached to the chasis. I'm guessing it wouldn't be a good Idea to ground it either.

It very likely has (had :nono:) a live chassis, (and no transformer) - doesn't surprise me in the least that it went BANG !
 
Being I know little, I would never dream of changing the wiring of a device that people far smarter than I designed.

What I do though is always check the outlet with an outlet checker to make sure the wiring is correct.
 
First, you need to understand how the 3 wire grounded circuit works. The hot side (120 volt potential, and yes the narrow blade of the polarized plug) delivers the current. It is usually fused the minute it enters a piece of equipment and then goes to a power switch, then to a transformer. All stereo equipment works on DC voltages, so that is why there is a transformer. The neutral is connected to the ground in your electrical circuit breaker box and is used to complete the 120 volt circuit. The circuit breaker box has 2 120 volt circuit in it. When you connect the 2 120 volt circuits in series, you get 240 volt, which is used to run your electric clothes dryer or kitchen stove, which requires high amount of current to operate. The third wire, the ground also goes to the circuit breaker box and then goes outside to a very long copper ground rod that is pounded into the ground outside of your house. The size of your electrical service is determined by 1) the gauge of wire to your house from the electrical company, and 2) the size of your mains breaker.

2 prong wiring to lots of equipment, simply is all that is required. The is little to no risk of electrical shock, under normal, expected operating conditions. As an example, a vacuum cleaner does not have a ground wire. It's usually used on carpet, which is an insulator, and the vacuum is usually made out of plastic so there literally is no way to complete a circuit, and get electrocuted.

Toasters are 2 prong, and usually made of metal, but they are used in the kitchen where GFCIs are required. GFCIs monitor current from hot to neutral, and if they are not equal, the GFCI trips, cutting all power to the outlet.

Now, most hifi equipment is made of metal, but you as the user are expected to operate it within the home, not on wet concrete floors, or use said equipment with frayed power cords. They are safe as long as you abide by these simple rules. When you decide to take your receiver outside in the rain, that trouble can certainly come about.

Three wire cords for amps certainly are now popular, as are IEC sockets. But actually, all of these amps could have gotten a UL listing with just a 2 prong plug. The manufacturers that promote the 3 prong are using it as a marketing tool.

Also, the three prong plug can lead to ground loops for hifi equipment. If each component has it's own ground and if there is even the smallest milliamp leak of current to ground it will create hum.

Wayner
This is certainly the most informative post on the thread. Two notes of meaningless detail --
1. Yes, in effect two 120 volt circuits feed your house's main panel. The reason for this is that the transformer on the pole is actually center tapped - the center tap is neutral and does get connected to earth ground at some point thru said metal stake into the actual earth. There is 120V to each side of the center tap. Both hots used like for the dryer, water tank, stove/range use the full 240V. So technically as stated both are the seriesed "two hots" from the pole transformer. Normal duplex outlets only have one side of the center tap used for the "hot"-the neutral is the center tap.

2. When current flows not only the "hot" carries the current but of course the neutral does as well in equal amounts. If the amounts are not equal the extra current must be flowing to "earth", and this is the principle behind the GFCI and why they work on ungrounded two pronged outlets. Any difference of more than a couple milliamps between the two prongs and they trip open.

I was sure an electrician would chime in on this immediately, but then again, perhaps not all or many know all the details of these theories in wiring or equipment. You dont need to know to successfully wire stuff up.

No excuse for reversed outlets however, unless they were not installed by an electrician, since the first lifesaving motto they all learn is "black to brass saves your ass". Get that wrong even once and I believe "your fired".
 
As stated in a early post, the neutral and the ground are connected in the panel, its referred to as bonded. When you get a new panel there is a screw in the panel which you screw into the netural side which then bonds it to the grounded section. You would not put that screw in if you wanted to use the panel where you plan on your grounds to be isolated. In an installation where you use isolated grounds, the recepticals will have orange on them, that designates an isolated ground receptical.
 
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