Open Case or Closed Case? - EMI / RFI

[cheez]

What platform will generate less amount of EMI (Electromagnetic Interference) or RFI (Radio Frequency Interference)? A computer in a closed case or a test bench (motherboard, CPU, and all other peripherals exposed, but mounted on a metal tray)? It will be placed inside the large wooden wine storage furniture with the doorz closed.

This is in regards to the sound card in the system as to how much it will get infected from the EMI/RFI.


Anyone has experience? Thoughts? before I take any action?


umm.... thanks?

:ninja:

 

[kornphlake]

Encapsulating everything in lead won't make any difference you've got top of the line power cords and interconnects that should snuff out any EMI/RFI

 

[LoveMachine]

Depends on which system induces the most EMI, either the "internal" system of the components of your PC, or the "external" system on the outside environment (e.g. nearby TVs, AVR, etc.). A metal case might block a very small amount of outside EMI from coming in, but it might also act as a reflection chamber as well. Regardless, it's a VERY small contributor. I'd surmise that the best thing you could do would be to run a high quality power supply to the computer, giving a clean electricity source. Silent PC Review has tested multiple PS's. Might be a good resource.

The worst interference I've ever had was from Comcast Cable. The coax produced a horrible hum to any sound source that was remotely connected to it. For example, going from the wall into the tuner box, to the TV, and only an HDMI cable going from the TV to the AVR (different wall plugs even), still produced a bad hum.

 

[cheez]

Thanks kornphlake. I hope your right. I will then gut out all the components from the case and rebuild as a test bench. Because my audio RCA cables aren't long enough to reach my sound card, my case is currently set upside down. That's how it's been running for a few weeks now. I didn't notice any gheyness yet.

No I haven't received my power cable yet. It's taking so long, nearly a month. And no it's not the top of the line. Hey, I can't talk about power cable as the Mods warned me not to otherwise I'll get in trouble... so plz don't discuss about power cable thx.


cheez

 

[cheez]

Depends on which system induces the most EMI, either the "internal" system of the components of your PC, or the "external" system on the outside environment (e.g. nearby TVs, AVR, etc.). A metal case might block a very small amount of outside EMI from coming in, but it might also act as a reflection chamber as well. Regardless, it's a VERY small contributor.

I have a plasma TV on a wall mount, about 10 inches above the wine storage furniture. And two powered speakers sitting on top of the furniture close to the edges. I don't have an external receiver, STB, or any of that sort.

I'd surmise that the best thing you could do would be to run a high quality power supply to the computer, giving a clean electricity source. Silent PC Review has tested multiple PS's. Might be a good resource.

Thanks for the recommendation.

The worst interference I've ever had was from Comcast Cable. The coax produced a horrible hum to any sound source that was remotely connected to it. For example, going from the wall into the tuner box, to the TV, and only an HDMI cable going from the TV to the AVR (different wall plugs even), still produced a bad hum.

Yes I do have Comcast Cable, with coax cable running from the wall outlet to the modem only, for internet. Good info. Thanks for the heads up! Pretty amazing how small things can be overlooked.^_^


cheez

 

[cheez]

Guys I have some good news, really good result.

Evidently the EMI / RFI is all around us, around the components, TV, audio system, radio frequencies, heck even our bodies generate some interferences.


I have done ALL of the following and the humming sound from the mid range driver from my right speaker in my audio system has now reduced tremendously. I can now barely hear humming sound at all. I would have to stick my ear right on the driver to barely hear it.

• Dropped the internet service. Pulled out the network cable from the PC. Pulled out the coax cable from the wall outlet.
• Removed ALL of the fans from my computer test bench and installed a watercooling system, with 80ft loop run all the way to the bathtub in bathroom. The water pump is submerged in the 50 gallon water.
• Lowered the Vcore from 1.35V to 1.07V for CPU; and ALL of the rest of the system voltages to the lowest setting except for memory at 1.8V as it didn't like below that. System running at stock CPU clock but memory running at the same speed as the CPU (1:1 ratio).
• Replaced the 3x 10k RPM WD Raptor hardrives with a SSD for the OS drive. Storage drive is WD Red NAS drive. - Significant improvement in EMI reduction
• Placed all components on the foam padding to reduce noise / vibration
• Set the test bench away from the speakers. Test bench is inside the wine storage cabinet which is made with thick solid wood. This is to reduce vibration.
• Lowered the brightness on the display of the plasma TV to MINIMUM. HUGE reduction in RFI/EMI interference.

All this added up, and now humming is literally gone. It also reduced the hissing sound from my tweeters, but not as drastically as it did with the humming. Still, good improvement.


Big thanks goes to Patrick. Some thanks goes to a few other members here at anandtech.


P.s. the RCA cables for my speakers are the cheapo $25 Wireworld Terra-6 RCA cables. These are not shielded I believe.




cheez

 

[alkemyst]

An open case will have the potential for more EMI/RFI...I doubt you will notice a problem if using mainstream components.

The biggest problems are light ballasts and dimmers.

That said running an open case is risky at best esp in "Home Theatre".

 

[cheez]

An open case will have the potential for more EMI/RFI...I doubt you will notice a problem if using mainstream components.

The biggest problems are light ballasts and dimmers.

That said running an open case is risky at best esp in "Home Theatre".

It suffered from severe humming / hissing noise from speakers when the system was in the case all covered.


cheez

 

[cheez]

Guys, I have a critical update.

All these tweaks (a couple of posts up) helped significantly as the humming and hissing had reduced to a level where I could barely hear even when I was only a few feet away from the speaker. But I can hear a little when I put my ear closer to the driver.

When I changed the background color in the plasma TV to anything other than black (blue, pink, green, light red, etc) the hiss and humming noise increased. If I set it to white background the noise increased even more. Turning off the plasma TV altogether was best, as it lowered the noise even further. But I can't do that as I need video to control my PC to do thangs you know?

I had tried $150 Wireworld Oasis RCA cables in the past and that made no improvement in the hissing / humming noise. I had also tried $200 Audioquest Sydney cables that made zero difference. So I thought it's not the cable related hmmmm.... Must be ground loop issue? Well guess what that wasn't it.

I just received the Coconut-Audio White Night RCA 1.5m Ultra cables from Patrick two days ago. I replaced the $25 Wireworld RCA cables with these. It's totally silent. No matter what I did to it it was dead silent. Turning the TV on or off or increase brightness didn't matter. It was just dead silent.

This tells me that I was suffering from RFI/EMI that the other cables "collected" or "picked up" along the way - from the output of the PC to the input of the speakers. I also had a small amount of hiss in the left speaker, that's gone too now.

Problem solved 100%.

Just wanted to report my finding.


Thanks,

cheez

 

[metril]

Did you know that blood has a lot of iron in it?

Apparently, iron tends to amplify EMI when it isn't treated and combined with heavy metals. Luckily, lead can isolate iron. Might want to try some lead tablets (with food) to really get rid of all that annoying hissing. I thought I'd be helpful and pass this along. It might give you even better sound. Sorry if this comes off as a troll. I just like really clean sound.

Disclaimer: I am not a doctor. I do not know about any harmful effects of lead. I am merely trying to pass on possible useful information. These statements have not been validated. It is the responsibility of the end user to ensure his/her safety.

 

[mikeford]

Ugh, what a low knowledge thread.

Case closed means less emi/rfi and better cooling in most situations without some kind of external air flow. Look up Faraday shield, its the basis for Tempest.

Hum is from grounding issues and indicates poor AC house wiring or most commonly a poor ground someplace in the cable power system. A ground isolator on the cable connection fixes most problems. With bad house wiring you can run everything off the same line, or try a line isolation filter.

Hiss is often mismatched gains and is more a sign of a noisy component, as in low signal to noise or noise slipping into the system from some input even if unused. You should be able to track it down by going to a system with the bare minimum of things connected, and slowly adding one item at a time until you find the source.

 

[mikeford]

Some cables only connect the ground to one side, so no path for chassis ground, but there is no cable that would magically reduce hum other than via ground issues without reducing all the low end bass.

 

[cheez]

Ugh, what a low knowledge thread.

Case closed means less emi/rfi and better cooling in most situations without some kind of external air flow. Look up Faraday shield, its the basis for Tempest.

Hum is from grounding issues and indicates poor AC house wiring or most commonly a poor ground someplace in the cable power system. A ground isolator on the cable connection fixes most problems. With bad house wiring you can run everything off the same line, or try a line isolation filter.

Hiss is often mismatched gains and is more a sign of a noisy component, as in low signal to noise or noise slipping into the system from some input even if unused. You should be able to track it down by going to a system with the bare minimum of things connected, and slowly adding one item at a time until you find the source.

Although the speakers are now dead silent, once a while they pick up slight amount of hum when the plasma TV brightness is jacked up. And of course it was much worse before I did the "tweaks and cables" listed above. Nope, it's not the ground issue as if it is it would hum continuously. It's virtually gone, both hiss and hum. The hum I was getting came from interference in the air, nearby the TV. This was an obvious proof as I have been testing it.

I wasn't saying open case is better than closed case. When I was in closed case I didn't do any of the tweaks I performed as above so I was getting lots of hiss and hum out of the speakers.

Don't just go around and crapping threads around because what you think is right or wrong. You are not always right. You act like a smart butt, don't do that around here..


cheez

 

[Soundmanred]

Facts and scientific method.

Speculation and voodoo

cheez

I totally agree with mikeford.
(My username isn't because I like Sounds, man.)