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This Grounding Thing
- Thread starter speakerman1
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Siempre, siempre, siempre 
DOH Dude, always have a proper ground, and just because the outlet has three holes doesn't mean the outlet has been properly grounded, this is very important as well. get one of those plug checkers like this GB, you want the two amber lights lit, if you just have one lit or
the red one, you have a problem.
I had dedicated, true grounded lines with outlets put in the main room, worth every penny!! I highly suggest you check your house. and it's not just SS gear, those Cary's demand the best you can give them
DOH Dude, always have a proper ground, and just because the outlet has three holes doesn't mean the outlet has been properly grounded, this is very important as well. get one of those plug checkers like this GB, you want the two amber lights lit, if you just have one lit or
the red one, you have a problem.I had dedicated, true grounded lines with outlets put in the main room, worth every penny!! I highly suggest you check your house. and it's not just SS gear, those Cary's demand the best you can give them
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, you also said older SS gear too, what would that be? And the IEC plug to what?
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It is hard to retrofit some of the early SS or tube gear because the engineering back then was all about safety, not so much about the sound quality and most homes had two-prong receptacles, not three. With a metal cabinet there was the possibility of a shock hazard when connecting multiple pieces of gear together.
An example, if the amplifier power wire is zip cord and the non polarized plug (like those found on Phase Linear gear) is connected to the wall, the normally hot wire is on the right of the receptacle, so the wire on the left is neutral and connected to common back at the electrical box and grounded to the amp chassis. If the preamp is wired the same way and you turn the power plug over, you have just connected the hot wire to the chassis of the amp through the grounded interconnects - boom. For this reason the chassis was not grounded with any type of two conductor power wire.
To use an IEC power cable or jack, you have to be careful grounding the chassis. The reason is that the amplifier DC common floats above the AC ground by several volts, you can measure it by using a three-prong extension cord on a two-prong power cord and check the AC voltage between the ground of the extension cord and the chassis. You have to use a systems approach to grounding the amp and everything it touches, it is not a simple exercise, that is why Lee and I left it alone. We both may go back and rewire the amps for proper three-wire grounding but that will take some serious thought to avoid inducing DC voltage back into the electrical panel, placing voltage on the chassis if the grounding lug is not at absolute ground, or creating a ground loop between the power wires and the interconnect shields. Not as simple as placing a ring connector from the green wire on the chassis, in some cases.
Mark
An example, if the amplifier power wire is zip cord and the non polarized plug (like those found on Phase Linear gear) is connected to the wall, the normally hot wire is on the right of the receptacle, so the wire on the left is neutral and connected to common back at the electrical box and grounded to the amp chassis. If the preamp is wired the same way and you turn the power plug over, you have just connected the hot wire to the chassis of the amp through the grounded interconnects - boom. For this reason the chassis was not grounded with any type of two conductor power wire.
To use an IEC power cable or jack, you have to be careful grounding the chassis. The reason is that the amplifier DC common floats above the AC ground by several volts, you can measure it by using a three-prong extension cord on a two-prong power cord and check the AC voltage between the ground of the extension cord and the chassis. You have to use a systems approach to grounding the amp and everything it touches, it is not a simple exercise, that is why Lee and I left it alone. We both may go back and rewire the amps for proper three-wire grounding but that will take some serious thought to avoid inducing DC voltage back into the electrical panel, placing voltage on the chassis if the grounding lug is not at absolute ground, or creating a ground loop between the power wires and the interconnect shields. Not as simple as placing a ring connector from the green wire on the chassis, in some cases.
Mark
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Ok I understand. I'm still thinking here. Houses are wired way different today. I mean I have GFIs in my garage.So that if voltage even minutely is on that grd.it trips. My house is 5 years old. By using The IEC you willhave the + correct and the - correct and the grd. There is no way to wire it different.Unless you just don't know what the color screws are for. So why would it be hard to grd.? You can't get the + and - swapped plugging it into the wall.
Larry
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In the old 2 prong days a lot of home electricians didn't even consider which side of the AC they hooked to the outlet sides to which wire. I ran into this when I hooked up a computer to cable, wham a great ground, result, welding, fortunately not long enought to cause damage. I fixed the problame and then ran a new outlet for my cmputer with a proper ground.
Jim
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Jim, That is our point exactly. With a two-prong, non-polarized cord, you could flip it either way. "Hot" could be on the left wire or the right wire as it goes into the amp. On the older gear those two wires typically go to a fuse on one wire and a switch on the other wire and then right into the transformer - no polarity.
With the IEC, you have to get it right. You want to switch the hot wire not the neutral. Because if you switch neutral the rest of the amp is still hot. If you open it up to make a measurement, you could get fried between the chassis (now grounded back to the electrical box) and the transformer, fuse, or any part of the amp wiring that connects back to the transformer primary where the 120 VAC is sitting. If fact, it is best to switch both legs of the input power coming in to the amp on a DPST switch rated above the mains voltage and 150% of the current. The other possibility is a short in the transformer, it will probably go to ground and make the chassis live, not good unless the chassis is properly grounded and fused.
So on my Corcom IEC jack the hot wire is brown, the neutral wire is blue, and the ground wire is green with a yellow stripe. I will install a DPST switch on the brown and the blue wires, put the 10 Amp line fuse on the brown wire, and then wire it into the transformer. The blue wire will come off the switch and right into the transformer. I will place .1 mF, 275 VAC, X-type capacitors across the poles of the switch to absorb the arcing in the switch. The green ground wire will be bolted to the chassis and wired to a parallel 35A bridge rectifier as a path for fault currents, a 10 Ohm, 5 Watt resistor to reduce loop currents, and a .1 mF 250 VDC capacitor to block RF interference; then on to the ground connection of the internal electronics.
Mark
With the IEC, you have to get it right. You want to switch the hot wire not the neutral. Because if you switch neutral the rest of the amp is still hot. If you open it up to make a measurement, you could get fried between the chassis (now grounded back to the electrical box) and the transformer, fuse, or any part of the amp wiring that connects back to the transformer primary where the 120 VAC is sitting. If fact, it is best to switch both legs of the input power coming in to the amp on a DPST switch rated above the mains voltage and 150% of the current. The other possibility is a short in the transformer, it will probably go to ground and make the chassis live, not good unless the chassis is properly grounded and fused.
So on my Corcom IEC jack the hot wire is brown, the neutral wire is blue, and the ground wire is green with a yellow stripe. I will install a DPST switch on the brown and the blue wires, put the 10 Amp line fuse on the brown wire, and then wire it into the transformer. The blue wire will come off the switch and right into the transformer. I will place .1 mF, 275 VAC, X-type capacitors across the poles of the switch to absorb the arcing in the switch. The green ground wire will be bolted to the chassis and wired to a parallel 35A bridge rectifier as a path for fault currents, a 10 Ohm, 5 Watt resistor to reduce loop currents, and a .1 mF 250 VDC capacitor to block RF interference; then on to the ground connection of the internal electronics.
Mark
Hi Lee and Larry
NEITHER side of the AC line should EVER be considered ground and should ALWAYS be isolated from chassis (it is a violation of just about every safety agency to do otherwise). The 3 prong IEC C13 type connector provides for the 2 isolated AC inputs plus a 3rd safety (non-isolated) ground. The safety ground purpose is to tie the chassis to the ground stake in your house which usually is driven into the earth near your circuit breaker box. In the event that the insulation of one of the isolated AC inputs breaks down and shorts to the chassis, it provides a path for the resulting current to this earth ground which in turn pops your circuit breaker and preserves human safety. Without the safety ground, this AC isolation breakdown would end up energizing the chassis and presenting a human shock hazard.
With that said, using the third wire safety ground to tie to the chassis in your Phase Linear is asking for ground loop problems which usually always shows up as hum. This is because the DC ground in the Phase Linear is also tied directly to the chassis. To be successful in adding the IEC safety ground attachment to your Phase Linear chassis, you will have to isolate the amp DC ground from the chassis at the multiple tie points that are in the original design (I think there are 2 of them, the middle leg of the two small 3 terminal barrier strips on the amp back wall). Since I have never tried this, I do not know what "other" noise problems will result from isolating the Phase Linear chassis from DC ground and I would have to resort to the "your mileage may vary" phrase.
I don't know if this is helpful at all or not.
NEITHER side of the AC line should EVER be considered ground and should ALWAYS be isolated from chassis (it is a violation of just about every safety agency to do otherwise). The 3 prong IEC C13 type connector provides for the 2 isolated AC inputs plus a 3rd safety (non-isolated) ground. The safety ground purpose is to tie the chassis to the ground stake in your house which usually is driven into the earth near your circuit breaker box. In the event that the insulation of one of the isolated AC inputs breaks down and shorts to the chassis, it provides a path for the resulting current to this earth ground which in turn pops your circuit breaker and preserves human safety. Without the safety ground, this AC isolation breakdown would end up energizing the chassis and presenting a human shock hazard.
With that said, using the third wire safety ground to tie to the chassis in your Phase Linear is asking for ground loop problems which usually always shows up as hum. This is because the DC ground in the Phase Linear is also tied directly to the chassis. To be successful in adding the IEC safety ground attachment to your Phase Linear chassis, you will have to isolate the amp DC ground from the chassis at the multiple tie points that are in the original design (I think there are 2 of them, the middle leg of the two small 3 terminal barrier strips on the amp back wall). Since I have never tried this, I do not know what "other" noise problems will result from isolating the Phase Linear chassis from DC ground and I would have to resort to the "your mileage may vary" phrase.
I don't know if this is helpful at all or not.
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