Noise heard through Sub when laptop plugged in...

[Blackstone]

And if it's me that touches the ungrounded box .. then so be it .. who cares.

[MatrixDweller]

I guess that is the question then...do you really care.

So from now on throw caution to the wind. Drive with out your seat belt on, smoke 3 packs of cigarettes a day, operate heavy machinery while intoxicated and dive in the shallow end.

If a unit does not have a ground prong then it does nothing with grounding. If a cheater plugged device had a short to its chassis it's not going to magically attach itself to another device's ground. The only way would be to attach a wire to each device's chassis and connect them all together so they would share one device's ground prong. In that case I don't know why a cheater plug would even be used.

The neutral wire will meet ground in the main panel but it's not the same thing. Large current on the ground will trigger a breaker whereas current on the neutral is normal.

[Blackstone]

Well I'm still a bit confused by what you're saying Matrix .. by .. "the ground perpetuating through the AV cables."

I know this site is called Home Theater Shack but my situation is a music studio.

Every piece of gear is going through the same power conditioner. The amp .. which theoretically draws the most power is grounded. Some of the gear I have only has two-prongs from the factory so is not ground-able. The remaining 3-prong gear has been lifted with a cheater plug. It's my understanding that I could have plugged the 3-prong gear into a power strip with a Ground Lift feature but that would achieve the effect.

My understanding is because they are all on the same >power< circuit, then a short should be grounded by the amp. I never had any expectation the AV cables would enter into the picture.

I mean I touch phono connectors all the time and don't get electrocuted. The exception to this would be if I was running 48 Volt phantom power for microphones .. where I am aware there is a risk of electrocution.

Again .. There is tons of gear that comes from the factory with only two-prongs .. how are these manufacturers not putting end users at risk? (Cell phone chargers, routers, USB hubs, 16 channel mixers). And if they are .. how do you remove a ground loop from a collection of gear where two or more items have 3 prongs while at the same time securing even the dumbest user against faulty gear and electric shock?

[Blackstone]

btw: Here's a bit of my rig


Wall socket

-- Rack mount power conditioner/distribution (3-prong)

-- 1400 watt power amp (3-prong) grounded
-- Tape deck (2-prong)
-- Power strip (3-prong)

-- Laptop (cheater plug)
-- Laptop (cheater plug)
-- 24" monitor (cheater plug)
-- 8 channel digital mixer (cheater plug)

-- Power strip

-- 16 Channel mixer (2-prong)
-- Synthesizer (2-prong)
-- Synthesizer (cheater plug)

You're saying this is unsafe? If so what do you do about it? What about the factory 2-prong gear?

[MatrixDweller]

Anything with a cheater plug will not be grounded. It doesn't matter if they are plugged into a power conditioner. The ground on the device must connect to the mains ground (outlet's ground) somehow.

The laptops are probably safe. The ground wire on it would most likely be for power regulation within their power supplies. The monitor would be the same. Still a short inside either could present a shock hazard if the right part of the case were touched.

The synthesiszer and mixer could present a shock hazard. If the mixer or keyboard were to form a short to ground then touching a metal screw, metal casing, etc could be an electrifying experience. The cases/chassis would be tied into the ground on the circuit boards.

2 prong devices deal with shorts differently and do not bond into the chassis for grounding.

The reason why you are most likely hearing some ground loop hum is that one of the devices is bleeding of a little current to ground or there is some inductance/interference on one of the ground lines caused by thin poorly shielded power cables.

The following has some fairly good advice:
http://www.epanorama.net/documents/g...m_solving.html

More on 2 prong vs 3 prong:
http://www.howstuffworks.com/question110.htm

[Blackstone]

Hmm ... interesting .. well I guess this is a bit more involved than I thought .. all I really wanna do is make music .. now I have to be an electrician too? .. lol

Well I'll talk to my keyboard tech and see if he can give me a simple way of setting up my studio so it's safe >and< quiet.

Thanks Matrix

[wglyons]

I had this problem...I was plugging my laptop into the power strip. Once it was unplugged and on battery power, the noise went away. So, I tried plugging the laptop into the back of the receiver. Not saying its the best scenario, but it completely solved the noise issue...