really? .89c ground lifters?

Soundgasm,

JMHO if you are going to lift the ground do it on all the three wire cord and plug audio equipment.

Make damn sure if multiple dedicated branch circuits are used the circuits are all fed from the same Line, leg, of the electrical panel. Use a volt meter to confirm.....

The object is to not have anything within arms length that is grounded. If a ground fault current path does not exist there cannot be a difference of potential for an electrical shock to happen.

Now of course if the floor is bare concrete or any other conductive surface lifting the ground would not be a good idea.

All the PS Audio power cords have a removable ground pin for this very reason. They seem to be well thought out plugs.
04-18-10: Mulveling

True,... but you will also notice they are not approved by UL or any other recognized testing agency.

On my system the solution is open the IEC Oyaide (equipment end) and lift the ground.

The reason to not do this at the wall is that would leave the ground as potential antenna into the equipment. This method leaves the wall plug ground pin in place which helps secure connection, especially for heavy AC cords.
04-17-10: Albertporter

Albert is not alone in his thinking about the lifting of the equipment grounding conductor at the source end of the PC acting as an antenna. There are a few EE on AA that say the same thing.
Remember the other end of the power cord's equipment grounding conductor is still connected to the case, chassis, of the equipment. One other point that comes into play is the small induced voltage from the hot conductor of the PC that crosses over into the lifted equipment grounding conductor. With the induced voltage EMI/RFI noise can travels up the PC equipment ground conductor to the chassis and on into the signal ground of the piece of equipment as well through ICs to other pieces of equipment.

In previous incarnations of my system, it worked well to have just the preamp with a 3-prong plug, and the other components (phono stage, power amp) on a 2-prong plug. Putting a 3-pong plug on my old power amp yielded a loud BUZZZ. However, my new monoblock amps (maybe due to their balanced input stage) and phono stage are both doing just fine with 3-prong plugs as well.
04-18-10: Mulveling

I read this a lot here on Agon and AA where the preamp is used as the connection for the safety equipment ground for all other three wire equipment connected together by their ICs.
Star grounding.....

I have yet to read any post where a ground fault condition , say from a power amp, successfully passed through the ICs to the preamp signal ground > to the chassis > on out the PC > through the equipment grounding conductor of the branch circuit to the electrical panel causing enough current flow to cause the branch circuit breaker to trip open....
I would appreciate any links to the contrary.....

Jea48,
Could you explain "JMHO if you are going to lift the ground do it on all the three wire cord and plug audio equipment."?
I didn't quite get it.
Thanks
04-18-10: Maril555

First I do not advocate lifting the safety ground. But if you must, JMHO, it would be safer to lift the ground on all equipment that uses the safety ground. To receive an electrical shock there has to be a difference of potential, voltage, that a person's body comes into contact with. I personally would not rely on the ICs from a preamp to a power amp for a suitable ground fault path from the amp to the preamp. Instantaneous ground fault current flow can be well over 100 amps. Will the #20 ga wire withstand that amount of current flow long enough for the 15 or 20 amp branch circuit breaker to trip open. Better yet how is the output of the preamp jacks signal ground connected to the chassis? Could the path pass a high ground fault current flow?

Basically what I am saying if you have to lift the safety ground do it on all the equipment. Remove any chance of a difference of potential to a grounded object within arms length or from any part of the body to any electrically grounded object.

Food for thought. A bird perches on a high voltage wire and does not receive an electrical shock.
A squirrel jumps onto a high voltage wire and runs down the wire without a care in the world. His fate is in his method of dismount.

Why any manufacture of audio equipment today would still be designing and building their audio equipment using the old out dated AC safety equipment type of grounding beats me.

Double insulated type AC power wiring in their equipment would not cost that much more to produce.

I must assume from some that have posted here no one that lives in an older home that has only 2 wire receptacle outlets, (no equipment grounding conductor), has audio equipment that has three wire plugs.

UL should require all manufactures to build their audio equipment with double insulated power wiring or the manufacture would not get the UL label.

As an Electrical/Electronics Engineer, I am telling you that lifting the ground and you become a better ground than the house ground and electricity will take the easiest path to ground and that becomes you.

Say what? Please explain how the human body can be a ground for an AC grounded power system......

Also, the load in your home should be balanced on each phase. Having all of your high power equipment on one phase will overload the wiring, cause it to heat up (IxIxR) losses and cause the insulation to fail causing a major electrical fire.

We are talking about audio equipment here.... In most cases all the combined connected loads would only add up to around 8 to 10 continuous FLA at best... Most hair dyers pull more than that.

the human body is an impedance. resistance, inductance and capacitance. You have an impedance. If there is a system fault or a lightning strike, or some such, very high voltages can pass through the equipment through you to ground.

That is a lot different statement than the one I quoted of yours in my previous post......
Yes if any part/s of the body is placed between a difference of potential, current will flow through the contact points. If the voltage and current is high enough there will be electrical burns at the entry and exit points. And yes it can kill you deader than dead! In the case of a ground fault the current is non discriminating.... It will take any conductive path available to get back to the source. It likes the least resistive path but it will still take any available path.

We are not talking about audio equipment. We are taking about electricity, voltages, sometimes very high voltages, current and impedances. a blown transformer and you have very high voltage spikes, a shorted device or a failed tubed device and very high voltages hit you passing very high currents through your body. Since you are an impedance, small but there, you will draw very high currents.

You really need to go back and read my other responses to this thread.....

It's probably worth pointing out that the danger from lifting grounds is much higher with tube components. These typically have 300+ VDC - very deadly.
04-22-10: Auxetophone

The only way to get a shock from the B+ is to actually put yourself in series between the B+ and B- ..... Lifting the safety ground would not change the likelihood one way or the other.....

04-23-10: Atmasphere
Yes, it does not matter tube or transistor. The real issue would be if somehow there is leakage from a power transformer.
04-23-10: Atmasphere

Atmasphere,
Speaking of transformer leakage....
Say there is a slight leakage in the primary winding of the power transformer to ground, small, not enough current flow to cause an internal equipment fuse to blow.
Current flow to ground never the less. Could this small current flow cause a ground loop hum problem? (By leakage I mean other than capacitive leakage.)
Jim

I wouldn't call that a ground loop. If there was something like that, it would cause the ground to be noisy.
04-23-10: Atmasphere

Could it cause a ground loop hum?

Why would it be any different than ground current flow from a CATV system? In both cases current is flowing through the equipment ground. We know current will take any provided path back to the source. If the ground current flow is present what would prevent it also from flowing through the ics signal ground to other three wire cord and plug safety grounded equipment to get back to the source?

Actually, if something goes wrong with the equipment - like a B+ wire touching the chassis - you're better off sending that to ground and blowing a fuse, than letting it sit out there to electrocute your kids.
04-23-10: Auxetophone

Auxetophone,
If B+ were to short across to the chassis the power supply would overload and hopefully blow a fuse, that is if the equipment has any power supply overcurrent protection. B- is usually connected to the chassis.....
Again in this case the safety equipment ground would not make any difference connected or lifted.

The Link you provided is in regards to three wire cord and plug equipment connected to an AC grounded electrical system. I am familiar with the article. The article tells it like it is.....

...how can I tell whether my equipment is a three wire cord and plug deal or the kind that's safe?
04-24-10: Auxetophone

Auxetophone,

In the case of a three wire cord and plug if the equipment ground is not lifted and the electrical continuity integrity of the branch circuit safety equipment grounding conductor is good all the way back to the electrical panel the equipment is for all practical purposes safe. (Three wire plug? 2 straight blades, hot and neutral, with a round ground pin. USA)

Here is a stickler though.... More and more equipment may use an IEC plug on their equipment with a 3 wire cord and plug. If the the IEC plug is inspected you may find there is only 2 blades, the hot and neutral. No equipment ground contact. In this case the equipment was built with double insulated AC power wiring. The equipment grounding conductor of the power cord is not used.

The reason for the standard IEC plug,(minus the ground pin), on the back of the equipment? The consumer can use 3 wire cord and plug after market power cords.

Equipment with fixed power cords if the equipment ground is used must have a 3 wire cord and plug. (Hot, neutral, and equipment grounding conductor.)

Equipment with a fixed power cord that uses double insulated AC power wiring will use a 2 wire cord and plug. The neutral blade on the plug will be slightly wider so as it will only plug into the receptacle in one direction. The plug is polarized. This is needed so the switch and fuse protection for the equipment is in series with the hot conductor. Also for the proper AC polarity orientation of the power transformer, that is if the manufacture checks every transformer before installation.... The big boys do... Every power transformer.

Also, some equipment with three prong power cable actually have the ground lifted inside the chassis. I've owned several amps wired this way.
04-25-10: Albertporter

If the amps are UL and or CSA listed then that would imply the AC power wiring of the equipment is double insulated thus meeting UL/CSA standards.

I would rather see the manufacture of the equipment use a C-14 or C-20 plug on their equipment with the ground contact pin removed. That way the consumer/user would know if an equipment grounding conductor was needed for the equipment. Or better yet how about the manufacture be required to print on the back of the unit along with the AC power consumption and Hz if the unit is wired with doubled insulated AC power wiring.

IEC connectors are the only UL/CSA listed plug and socket that I know of that can be used for both 120Vac as well as 220Vac. Can't do that with any NEMA plugs or receptacles. The IEC plug is the only one I know that can be used in electrical equipment and float the equipment ground contact. You could not do that with any NEMA two wire with ground Plug.

So I guess the question to be asked, does my equipment that uses IEC connectors use the safety equipment ground? No equipment ground contact pin in the IEC plug, no....
If the ground contact is present on the IEC plug then the only 100% sure way to know is pull the top cover off the equipment and look inside.

Could use a meter and check for continuity from the equipment ground contact of the IEC plug to the chassis. If the meter shows short then yes the ground contact is connected to the chassis and the equipment ground is needed for safe operation.

If the meter reads infinity/open I would not bet the bank 100% on the reading. Can you say 100% both test probes were making good contact? Pop the hood and look inside....
Or you could contact the manufacture.