Computer Shielding

[mhuss]

My left monitor (a Dynaudio DBM50) is making odd computeresque noises, and it happens to be about one foot/25cm above my (home-built clone) PC. I have tried moving the AC and signal wires as far as possible away from the data wires, with no improvement. The previous monitor (an M-Audio) had the same problem, and I've tried swapping L/R connections and monitors with no change, so I am pretty sure it is direct radiation from the PC. The case is mild steel, very new, modestly ventilated, and has a low impedance to ground.

The most obvious solution is to move the PC, but that would be extremely inconvenient (connections for monitors, many USB connections, access to the optical drives in the box, etc.) Plus, I want to continue to keep it as far away as possible from my mixer, outboard, etc. I'm aware that 'real' studios have computers in adjacent rooms, but that's not always practical in your home office.

Is there any in-situ solution possible (short of mounting a well-grounded 50kg mu-metal plate under my desk)?

--mark

 

[eddperks]

Pretty new on the forums but I can share a similar experience. The radiated noise and interference from computers is nearly always from the switched-mode power supplies. If you have a look around you could probably upgrade it to one thats a lot more stable and has a heftier case in itself to restrict interference radiation, its a cheap(er) part to upgrade and is an easy install. I know you said moving the computer is awkward but a USB 3.0 hub with extension, VGA/DVI/HDMI extensions and kettle leads are actually fairly cheap and will be a more solid solution! Have you moved the computer around its general area to see if there is a position where less interference is coupled to the speaker and its lines?

 

[millzners]

When you restart the Cpu does the noise change or stop? What about when in sleep mode?  Try to see if picking up the monitor and moving it around gives you a sense of how far the two need to be apart to fix the issue.  Maybe just a few inches fixes it and you can get some risers for you monitors.

 

[millzners]

Also if it makes you feel better my one monitor picks up Fm radio. Fm!  Fm demodulation isn't something that usually happens by accident.

 

[bruce0]

One opinion....

While radiated noise linking is possible, it is hard to accomplish. 

Much easier to link noise through grounds, signal and power cables.  Although I admit that the single monitor showing noise makes it seem like radiation.

Change the speaker connections to eliminate any patch panels.  If you are using balanced connections make sure both ends are capable of balanced, or do unbalanced.

Unplug all the USB, one by one.  I have seen USB ground linked noise, I think the USB grounds are not necessarily the same as the computer grounds.

Run the computer power through conditioning if you have it, or through a different circuit if possible.

If it problem truly is radiated noise, the effect will decrease as the square of the distance.  That is if you move it twice as far away from the element receiving the noise, then the noise will be 1/4 the amplitude.  3 times as far, 1/9th the noise.  If that relationship does not exist, it is unlikely to be radiated noise.

 

[MartyMart]

I have my Mac pro tower on a separate and filtered power board from all audio equipment.
No noise, hum or "disk access" noise at all.
Seems like that is bleeding into your audio system through ground.
Only connection to audio is the FF800 cable to my RME - it's an expensive one with ferrite beads each end.

Mac pro is under my desk, perhaps 4-5 feet from audio rack ( all balanced ) and 3 feet below
main speakers and 24in monitors.

MM.

 

[abbey road d enfer]

The most obvious solution is to move the PC, but that would be extremely inconvenient (connections for monitors, many USB connections, access to the optical drives in the box, etc.)

Have you actually done it, temporarily, just to make sure your diagnostic is correct?

 

[bruce0]

Confused (sorry). 

mhuss - what are the computeresque noises, buzz, hum, chatter any further description might be helpful.
Marty Mart - do you have a noise problem with a mac-pro?

I have had problems connecting to two unbalanced monitors using a common ground through a balanced patch panel.  Solved making the grounds independent (these powered monitors have switched mode supplies in them).  Also had a bad cap once in a monitor SMPS - made it noisy (and it was an m-audio monitor) - leave them on all the time, cook the filter caps (speakers are "vented" but not "ventilated"). 

can you just move the speaker for 5 minutes (put it on the floor in a pile of SMPS wall warts )  see if the noise changes?

The nastiest problem I have had with noise was some ground noise related to a usb connection to my roland keyboard, keyboard was connected to a patch panel, patch panel was ALSO connected to monitors.  Using Midi wire... no noise.  Using USB - low level computeresque noises (by which I mean an irregular HF whine probably around 5K Hz (by ear)).

 

[horvitz]

I get this sometimes but for me, it's my cell phone.  Specifically (I think.. no science here), it's data up/down in 4G.  It's really very prominent and only in my monitors, and definitely better or worse with proximity to my cell.  If I put my phone in airplane mode or hook it up to the wifi, it goes away completely.

 

[MartyMart]

Confused (sorry). 

Marty Mart - do you have a noise problem with a mac-pro?

No, not at all, used to with a much older model ( 8600 ) and since have always used a separate
filtered Power strip for computer only.

Was Data "chatter" when drive was being accessed and some high pitched interference.

Not had that for over 10 years now
M

 

[etheory]

Very interested in this discussion.
I have a FF800 also and I too suffer from disc-access related noise in every piece of audio in my studio.

I've tried a bunch of things, so far to no avail, but I can't help but noticing the FF800 is the common ground here.

I thought maybe a cheap firewire cable is to blame, however, if you say you have a good one, my next logic conclusion is to measure noise on the computer PSU to look for a correlation to disc access, or simply contact RME and see if there is some kind of regulation issue or grounding issue with the FF800.

The noise has been driving me mental for almost a year now. It's so so so so annoying.

To add insult to injury when my hard-discs go into park mode (due to inactivity) my system is crystal-clear perfectly noise free. So clearly I want this all the time.

 

[bruce0]

... a bunch of things, so far to no avail,

I always try to connect all the equipment to the same power source (so that ground loops that do occur are quieter).  You can change power sources to test, if it changes or gets worse, may be a ground loop.

Try: reduce the size of the system.  If it is just your computer, the RME and a set of headphones, is there noise?

 

[MartyMart]

Very interested in this discussion.
I have a FF800 also and I too suffer from disc-access related noise in every piece of audio in my studio.

I've tried a bunch of things, so far to no avail, but I can't help but noticing the FF800 is the common ground here.

I thought maybe a cheap firewire cable is to blame, however, if you say you have a good one, my next logic conclusion is to measure noise on the computer PSU to look for a correlation to disc access, or simply contact RME and see if there is some kind of regulation issue or grounding issue with the FF800.

The noise has been driving me mental for almost a year now. It's so so so so annoying.

To add insult to injury when my hard-discs go into park mode (due to inactivity) my system is crystal-clear perfectly noise free. So clearly I want this all the time.

OK.
Lets see how my setup is compared to yours ( come back to me on that one please )
Home studio is on a single ring main, computer on a fairly expensive filtered "power block"
The FW800 cable is short ( don"t whatever you do ,use the supplied one that's about 100 m long !)
probably a 1.5 m cable, integral ferrite beads at each end, can't remember the make but is was a good 25-35 Quid UK.
RME FF800 connections are all balanced from SSL X-Desk, all inputs are also balanced via Behringer DI800 and small
Mackie VLZ3 1402 sub mixer from some unbalanced Keys / FX.
System drives are all internal save for one Lacie FW800 external which is mostly powered down.
Power and audio cables don't run parallel wherever possible, power stay on the floor and audio is cable tied
and running just under my desk "worktop" in metal "tidy" cages ( Ikea )

That's about it, my cables are decent and the only "hum" is from an old Marshall JMP rack, that doesn't bleed into
the system though and neither does any disk access/computer noise - as i said earlier, noise free for almost 10 years.

Hope that helps ?

Marty.

 

[Dobrilo]

My left monitor (a Dynaudio DBM50) is making odd computeresque noises, and it happens to be about one foot/25cm above my (home-built clone) PC. I have tried moving the AC and signal wires as far as possible away from the data wires, with no improvement. The previous monitor (an M-Audio) had the same problem, and I've tried swapping L/R connections and monitors with no change, so I am pretty sure it is direct radiation from the PC. The case is mild steel, very new, modestly ventilated, and has a low impedance to ground.

The most obvious solution is to move the PC, but that would be extremely inconvenient (connections for monitors, many USB connections, access to the optical drives in the box, etc.) Plus, I want to continue to keep it as far away as possible from my mixer, outboard, etc. I'm aware that 'real' studios have computers in adjacent rooms, but that's not always practical in your home office.

Is there any in-situ solution possible (short of mounting a well-grounded 50kg mu-metal plate under my desk)?

--mark

Mumetal can help with low frequenies and it's hard to substitute it . If you have a problem with RFI than sheet of copper/ brass can help. Did you tried?

 

[marcus4audio]

Moving computer away from speaker sounds like best idea to me. And cheapest

 

[bruce0]

Distance is nature's mu-metal

 

[Dobrilo]

Distance is nature's mu-metal

It's a shame that distance can't be used for coil inductance increasing

 

[abbey road d enfer]

My left monitor (a Dynaudio DBM50) is making odd computeresque noises, and it happens to be about one foot/25cm above my (home-built clone) PC. I have tried moving the AC and signal wires as far as possible away from the data wires, with no improvement. The previous monitor (an M-Audio) had the same problem, and I've tried swapping L/R connections and monitors with no change, so I am pretty sure it is direct radiation from the PC.

"pretty sure" is not the same as "confirmed by experiment". Why don't you move the monitor or the PC to prove or disprove your conviction? I have never seen a PC radiating so much it creates noise in adjacent equipment.

 

[Dobrilo]

My left monitor (a Dynaudio DBM50) is making odd computeresque noises, and it happens to be about one foot/25cm above my (home-built clone) PC. I have tried moving the AC and signal wires as far as possible away from the data wires, with no improvement. The previous monitor (an M-Audio) had the same problem, and I've tried swapping L/R connections and monitors with no change, so I am pretty sure it is direct radiation from the PC.

"pretty sure" is not the same as "confirmed by experiment". Why don't you move the monitor or the PC to prove or disprove your conviction? I have never seen a PC radiating so much it creates noise in adjacent equipment.

But I've seen a speaker radiating to PC 

 

[gemini86]

If, in deed, the computer is causing problems... it's usually a sign that your PSU is failing or grossly under rated. Even when your PSU says it's rated for "650W" you have to look at how much power each rail is rated for, and how much your PC needs. Grab and Antek and be done with it.