[BackwardPawn]

I hope someone on this forum can help me with this one (or provide an alternative solution), as I've been searching forever and can't find the answer. I have a Creative x-fi Titanium HD in my PC, which is connected to the input on a dual mono tube amp. From the start, I've been plagued with noise on the ground wire. I hesitate to call it a ground loop since its not exactly a hum. When I move the mouse or the GPU/CPU starts crunching, it creates a noise that sounds like radio interference. My guess is that the PSU actually sending a signal down the ground wire, but I have no idea.

My initial solution was to use a different plug on the same circuit, which lessened the problem, but didn't make it go away. Solution two was to use a ground loop isolator. The isolator was grounded to the PC case. This worked better than solution one, but degraded the audio quality and didn't eliminate the problem. Solution three was to lift the ground on my amp power cords. The good news is this has completely eliminated the problem--absolutely no noise. The problem now is that I have a high current amplifier with no direct path back to ground connected directly to my head.

My initial logic here is that the box is connected to ground through neutral, therefore there is still a path to ground. The more I think about it, though, the more I'm unsure if I haven't created an unsafe situation. For example, on a ground-fault, will my breaker still open when the extra power is coming back over the neutral wire rather than ground?

I hope I've adequately explained explained the situation and my concern. I'm also hoping that someone tells me I just worry too much and I haven't created a death trap. But if I have created a death trap, how do I fix it without introducing noise into the amp?

 

[BackwardPawn]

With some further research, I'm thinking this may be alright because the computer power supply is connected to ground and I'm using RCA interconnects from the amp back to the PC. However, I'm not very knowledgeable about these things; hopefully, someone who knows more can give me an answer.

 

[sajunky]

Disclaimer: I seem to be a self-appointed expert in ground loops. Admins keep deleting my posts in Topping A90 thread and a reason is given is that nobody else says that A90 design is defective. .LOL.

I don't know what isolators were used. You are right, and it is noted that you found solution. Good work!

Computer metal enclosure is grounded and a ground is passing to the amp through a shield of RCA cable. It s safe as long as connection is reliable. It is not always a case, sh%$^ may happen. It is why I suggest to find out a ground terminal (possibly close to the RCA mounting point or solder it to this point) in your amp and wire it permanently to the computer case. A wire should be resonably thick multistrand copper (typical mains extension wire from electric store) and as short as possible.

When you do it, hum may come back, so get a ferrite clamp and place it over RCA cables (hook up both cables with one clamp). You can use two clamps, one on each side of the cables. The clamps should look like these: https://za.rs-online.com/web/c/passive-components/ferrite-cores/ferrite-sleeves/

EDIT: A place of attaching wire to the amp is important. If a ground of RCA connectors is the same as the amp chassis, do as above. If a chassis ground is separate (no DC short), attach a wire to the chassis ground.

 

[BackwardPawn]

Disclaimer: I seem to be a self-appointed expert in ground loops. Admins keep deleting my posts in Topping A90 thread and a reason is given is that nobody else says that A90 design is defective. .LOL.

I don't know what isolators were used. You are right, and it is noted that you found solution. Good work!

Computer metal enclosure is grounded and a ground is passing to the amp through a shield of RCA cable. It s safe as long as connection is reliable. It is not always a case, sh%$^ may happen. It is why I suggest to find out a ground terminal (possibly close to the RCA mounting point or solder it to this point) in your amp and wire it permanently to the computer case. A wire should be resonably thick multistrand copper (typical mains extension wire from electric store) and as short as possible.

When you do it, hum may come back, so get a ferrite clamp and place it over RCA cables (hook up both cables with one clamp). You can use two clamps, one on each side of the cables. The clamps should look like these: https://za.rs-online.com/web/c/passive-components/ferrite-cores/ferrite-sleeves/

EDIT: A place of attaching wire to the amp is important. If a ground of RCA connectors is the same as the amp chassis, do as above. If a chassis ground is separate (no DC short), attach a wire to the chassis ground.

Thanks for answering. This puts me more at ease that I can use the setup without risking electrocution. I think you are correct that a ground terminal is the best solution. If nothing else, the current setup will fry my PC in the event of a ground fault. Directing the power through the case rather than through the system should prevent that. I'll test out a ground wire between the cases and make sure that works before making it permanent.

EDIT: Can I solder a wire from the ground loop on the cheater plug back to the PC case or will this cause the hum to come back?

 

[BackwardPawn]

Here's the inside of the unit. It appears that on the RCA cables is attached directly to the chasse. Would I just need to put a ground connection of the outside of the case next to the RCA terminal?

 

[sajunky]

Most probably isolated, look at these red/white washers. It doesn't make sense to put colour markers inside other than for isolating. If you unscrew from the front you would see a plastic collar separating from the enclosure. Besides, it is a dual mono design. This is a second reason I think RCA connectors are isolated.

 

[BackwardPawn]

I guess I was looking at the wires coming off the PCB and assuming they were ground. What does this mean I need to do to properly ground the unit? Just attach a wire to the chassis? And if the RCA is isolated from the chassis does that mean the unit isn't grounded now?

 

[sajunky]

Shield of each cable is grounded directly on the corresponding tube socket. Find a place on the chassis where mains socket ground wire is attached to.

 

[BackwardPawn]

Shield of each cable is grounded directly on the corresponding tube socket. Find a place on the chassis where mains socket ground wire is attached to.

I think I may have solved the problem. I used the cheater plug on a single outlet ground fault circuit interrupter to cut the ground loop. Into the GFCI I put a three way tap to which I have both amps plugged in. It looks absolutely ghetto, and doesn't have a true connection to earth, but the GFCI should still detect faults and open the circuit before the power can do much damage (to either equipment or people).

 

[sajunky]

GFCI is called a leakage protector in South Africa, I didn't hear this name before, but google helps.

Nope. GFCI is not designed to detect missing ground. GFCI do compare current flowing in and out for two power lines live and neutral. If they are not equal, it means that there is a leak to the environment (it could be a ground wire or something completely different - your body in the worst case).

No such devices shouldn't be placed between your HiFi components. All devices of your HiFi gear should be powered from the same power outlet (or portable multi plug). Enjoy music.

 

[BackwardPawn]

GFCI is called a leakage protector in South Africa, I didn't hear this name before, but google helps.

Nope. GFCI is not designed to detect missing ground. GFCI do compare current flowing in and out for two power lines live and neutral. If they are not equal, it means that there is a leak to the environment (it could be a ground wire or something completely different - your body in the worst case).

No such devices shouldn't be placed between your HiFi components. All devices of your HiFi gear should be powered from the same power outlet (or portable multi plug). Enjoy music.

So, I used electrical tape to temporarily fix a piece of 16 AWG wire from my amp chassis to my pc chassis and tested the sound with different plug setups. With the ground-lift plugs attached to the amp, its still dead silent. Is there anything else I needed to do properly ground (obviously solder a terminal and use better wire)?

When I reattached the third prong, it was still quite noisy. I think the computer is dumping noise out onto earth ground and the amp is picking it up like a radio when attached.

And just to confirm, the above setup is better than using a ground lift on the GFCI because the GFCI won't open until power has fried my PC or me?

 

[BackwardPawn]

So, I used electrical tape to temporarily fix a piece of 16 AWG wire from my amp chassis to my pc chassis and tested the sound with different plug setups. With the ground-lift plugs attached to the amp, its still dead silent. Is there anything else I needed to do properly ground (obviously solder a terminal and use better wire)?

When I reattached the third prong, it was still quite noisy. I think the computer is dumping noise out onto earth ground and the amp is picking it up like a radio when attached.

And just to confirm, the above setup is better than using a ground lift on the GFCI because the GFCI won't open until power has fried my PC or me?

So here's a couple pictures of what I ended up doing. Could you please let me know if I'm doing anything I shouldn't (or if I need to do anything additional). I appreciate the help you've given me so far. First, I created a ground from one chassis to the other. Its currently a length of 16 AWG copper clad aluminum, so its really just for show. I'll have to get a length of 12-14 AWG copper wire and fix it to a terminal. When I get the proper wire, a ground fault *should* follow this path to the PC case and flow to ground, and not find a path back to ground through the user.

On the power delivery side, I've done the following (please tell me why you think this is bad): Mains power is being delivered through a surge protector to a single outlet GFCI (15A max). Its the same surge protector I have my PC on. I've split the GFCI with a three-way tap into which I've plugged the two amplifiers with their ground lifted. Lifting the ground is the only way I've found to make them usable due to the noise generated by the system.

If power on the neutral wire doesn't equal the hot wire, then there is a leak or fault and the GFCI should open in 1/40 of a second. Its probably not as safe as having a connection to earth ground through the breaker box, but it *should* prevent a prolonged flow of electricity to ground through the user. Please excuse the mess of cables, I undid the cable ties to move stuff around.

 

[sajunky]

A ground wire doesn't need to be so thick. It is currently thicker than 3 wires of your power cable plus isolation.

On the power delivery side, I've done the following (please tell me why you think this is bad): Mains power is being delivered through a surge protector to a single outlet GFCI (15A max). Its the same surge protector I have my PC on. I've split the GFCI with a three-way tap into which I've plugged the two amplifiers with their ground lifted.

It is why you have ground loops. You have two surge protectors, one on the PC, the other one on two amplifiers, plus monitor perhaps plugged-in somewhere else. Only two amplifiers take power from the same outlet, but I wrote in my previous message, it should be one multi-plug for all your devices. On the SA market it looks like this:
https://www.makro.co.za/hardware-au...-way-surge-multiplug-/p/000000000000280927_EA

Do you want to use GFCI? Check it out: If there is one in your distribution box or in the wall outlet, you don't need another one.

Do you want to use surge protector? Fine. Use only one surge protector for all your devices, followed by multi-plug:

wall plug --- surge protector --- multiplug    | --- device 1
                                            | --- device 2
                                            | --- ...
                                            | --- device n

A single multi plug. If number of your devices exceed capacity, get a larger multiplug. Extra splitters are not critical, but not welcome. It shoudn't have any overload switches, neon lights, etc. Any extra inductive devices (surge protectors, overload switches, filters or GFCI's) on the multi plug only do harm.

If power on the neutral wire doesn't equal the hot wire, their is an environmental leak and the GFCI should open in 1/40 of a second. Its probably not as safe as having a connection to earth ground through the breaker box, but it *should* prevent a prolonged leak of electricity to ground through the user.

Ground pin is required by general safety standards for the user equipment. It is different to the house electrical installation regulations that cover use of GFCI. If your house installation is certified, it has at least one GFCI protector in the distribution box. You don't need more.

 

[BackwardPawn]

You obviously know more about this than I do, so I'm not questioning what you say, I'm just trying to understand. When I plug the PC, amps, monitor, etc into a single multi-outlet surge protector, I'm getting ground noise that gets worse while the computer is busy. And its not a traditional hum, its static noise that sounds like EMI.

Breaking the connection to ground makes this noise go away, it seems to have nothing to do with where I plug it in (except that running extension cords into another room makes it lower). Nothing else I've tried gets rid of the noise. Ground loop isolator, running on the same plug, running on different plugs, changing power supplies, changing sound cards, etc. I agree that lifting the ground is unsafe and want to mitigate that as much as possible; hence the use of the GFCI.

I don't think American homes have GFCI in the breaker box (maybe new construction does). I'm pretty sure my 25 year old breaker box only trips when it detects power on ground or an over current, which is why we have separate GFCI outlets in the kitchen, bathroom, and outdoors. New homes probably do have this in the box. My thinking is using one for the amplifier will mitigate potential damage/injury by cutting off the power when a fault occurs. It seems no different, in theory, from a very old house without earth ground. They HAVE to rely on GFCI. If its safer to run this directly in the wall rather than on the power strip, or to run two of them without the splitter, or to find a three outlet version, I can do that.

Regarding the ground wire, I was looking at charts that recommended thick wire so that if the chassis is energized, there's less resistance over that path. However, if this is unnecessary, I'd prefer thinner wire. Also what type of grounding are you referring to. If this is just to keep the equipment at the same potential, I don't think its necessary as I don't hear the hum with the current setup. If this is grounding for a fault, won't the GFCI take care of that? That said, I'll do it if its safer.

Sorry, if I'm coming off as cross or obtuse, I really want to make the amplifier work properly and as safely as possible.

 

[BackwardPawn]

Any extra inductive devices (surge protectors, overload switches, filters or GFCI's) on the multi plug only do harm.

Based on this, is it acceptable to use the GFCI adapter in the wall and a three way tap to plug the two amps into it? Or buying a multi outlet GFCI adapter? I don't think a tube amp needs surge protection the way a PC does.