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Dealing with electric noise from computer

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genegold99

Weaksauce
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Jul 17, 2009
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I'd like to ask help with an electrical noise problem (no ground fault). I've tried both the Panamax M5300-EX line conditioner and Mapleshade power strip (Mk II Plus) with the same result. Starting with the Focal CMS 40 powered speakers and Dell monitor plugged into one of those two, if I plug the computer into my old style console the electrical noise is inaudible until I hold my ears tight to the speakers, and even then it's light. But if I plug the computer directly into the conditioning unit/strip, a high pitched hash/buzz that varies with the computer becomes audible from the listening position (3 feet) and at times is "plays" like soft music between the speakers. Of course, using the the strip gives a bit cleaner and more delicate sound than thru the console, but the hash/buzz is annoying.

So I'm wondering, is there a way to solve this short of a regenerator or a specially built PC? Thanks,

System:
i7-2600K, Win 8.1 Pro x64, 1 SSD, 2 HDDs
Ciunas dac, connected to computer with USB adapters (cable makes no difference)
Focal CMS 40 powered speakers (virtually unshielded)
Teresonic ICs (shielded like plane cockpit)
Power cords for speakers and computer: either MAC HC or Shunyata Venom 3 (shielded)
 
Just to clarify:
Your speakers and monitor are plugged into a a power strip.
If you add the computer to this same power strip, you hear buzzing?
If your computer is on another strip or plugged directly into the wall, the buzzing disappears?

If so, it sounds as if your PSU is a source of pollution. But this really shouldn't happen, so something seems amiss.

Just for further clarification, are you plugging each piece of equipment into the same bank on the Panamax? Individual banks are isolated, but individual outlets are not.
 
Yes, plugging the computer power cord into the Panamax or Mapleshade adds audible hash/buzz. Into the console instead, it becomes inaudible. Into the wall socket, directly to computer, it's audible, like the conditioners. It makes me wonder if the console is serving as a noise filter. But isn't that what these line conditioners are supposed to do to some degree? On the Panamax, since there are separate, isolated banks I spread things around: speakers in one bank, computer alone in another, etc. Moving them around made no difference. For those not familiar with the Mapleshade, it's here: http://shop.mapleshadestore.com/prodinfo.asp?number=MK2PS-PL (the bottom one).

It's hard to describe noise in words, but I'll try. There's an underlying low hash, with buzzing on top of it that varies, seemingly with what the computer is doing and even sometimes with the laser mouse (I moved the transmitter farther away to improve it). But I want to emphasize that this is all modestly audible to my mid-60's ears, just enough to annoy and at moments be heard between the speakers. It's not a loud buzz or hum, as if someting weren't quite connected. Thanks,

Update: I can add that it's apparently not a ground loop from the cable box or router either, as I unplugged the power and transmission cables from both ends without effect on the noise.
 
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The Panamax's bank isolation isn't perfect, and such a device is going to offer more filtering towards the wall outlet than between devices connected to it.

Anyway, I would just leave the computer connected separately from the speakers. Although I don't wish to discount what you are hearing, connecting the computer to a power conditioner shouldn't have any affect on the sound you hear. Again, the computer itself is a source of pollution, if you excuse the rhetoric, and computers in general are full of components which have the potential to add noise.
 
For the moment, the viable alternative is computer to the console, which is the only condition that renders the noise inaudible and causes the least sound degradation. I guarantee you there is an easily audible and pleasurable gain from taking the computer directly to the Mapleshade strip; I didn't use the Panamax long enough to find out. From the descriptions I find, this doesn't sound like a ground loop, but I'm going to give the Hum-X a shot to be sure. Thanks,
 
TESLA said it above. It's not a ground loop. It's back-emf from the computer PSU bleeding from the computer through the power lines to the power supply of the Focals. When they're all in the same strip, there's no filtering between them. In theory, it shouldn't be an issues with well designed SMPSUs, but companies are always Muntzing http://en.wikipedia.org/wiki/Muntzing to save a few cents. The Focals probably cut a few corners on their power supply. What PSU is your computer using? Power filtering varies by PSU and could make a big difference. Back EMF can be quite a problem, I had a refrigerator that had such a strong spike that about every six months it would blow out the control circuitry on my stove vent hood until they were finally put on different circuits.
That Mapleshade does approximately zero for any power line conditioning or filtering. I've built my own exotic power cables and power strips - they make no difference. In fact, increased bandwith hurts because it lets in high frequency noise. You need to filter out the garbage that the computer PSU is putting out (or get a new PSU). A simple isolation transformer is optimized for 60Hz and filters out high frequency garbage while costing 1/3 of the Mapleshade.
 
I'd isolate the speakers, it's a smaller load so you don't need as big (expensive) of a transformer. Ideally an isolation transformer should just be a big simple transformer designed to be at its peak efficiency at 60Hz. The best indicator is usually weight - there's no substitute for a mass of iron when dealing with magnetic flux. I'd see if I could get something locally or through Amazon so that you can return it if doesn't work.
 
Well, the speakers are isolated now with the Mapleshade strip or whatever I use; the noise problem is the computer line. Using the Xtreme Power Supply Calculator, the computer draws about 3 amps (~350w).
 
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Just received the Hum-X. Plugged the computer through it into the Mapleshade strip, along with the speakers and montiros, and the buzz/hash is eliminated. In fact, it's quieter than ever, with virtually nothing audible ear to speaker. The only question left then is effect on sound quality, and so far I haven't hear anything. it's ok in my system. The Mapleshade strip itself in that regard is a different matter tbd.
 
Just a question, are you using the speakers to play back audio from the PC? I didn't read that part anywhere in these posts.

That would mean you have a physical audio connection between them, regardless of where the PC and speakers get their power from.

Just trying to work out why the problem came up in the first place.
 
If by "play back" you mean play music, etc., from my computer, then yes, with a dac (usb adapters) and a pair of unbalanced ICs between the computer and speakers (each speaker has its own power). The problem came up when I added a power conditioner or strip (Panamax, Mapleshade) and plugged the computer into it, along with everything else. Then I discovered plugging it into the wall outlet directly got the same audible buzz/hash. Only into the old style console did it disappear. With the HumX, everything is now plugged into the Mapleshade strip, the HumX being used with the computer power cord.
 
genegold99 said:
If by "play back" you mean play music, etc., from my computer, then yes, with a dac (usb adapters) and a pair of unbalanced ICs between the computer and speakers (each speaker has its own power). The problem came up when I added a power conditioner or strip (Panamax, Mapleshade) and plugged the computer into it, along with everything else. Then I discovered plugging it into the wall outlet directly got the same audible buzz/hash. Only into the old style console did it disappear. With the HumX, everything is now plugged into the Mapleshade strip, the HumX being used with the computer power cord.
Click to expand...

Okay, I was just wondering if it was some ground loop issue. Obviously there is a physical connection (unless you use TOSLINK) that is also a potential electrical connection.

It is possible that the computer PSU has a bad earth, or maybe the PSU for the DAC (does this even have an earth pin??), or the speakers themselves, and it it using the earth from the PC, or DAC, or Speakers, creating a buzz.

I remember once having a power amp for a sub, and a HT amp at a customers, and the front left and right channels on the amp buzzed. Cutting the "shielding" from the interconnect from sub out to the power amp cured the problem. I believe that the power amp had a 3 pin plug, and the HT amp had only 2 pin plug (no earth).

It may not of been as simple as when the PC was using the same power that it was the PCs fault. Could just be a weird ground loop.

But we are all glad the problem is fixed :D
 
The Cuinas dac uses a separate internal battery, powered either from a PC-USB line or an external adapter, using a 2.1mm plug in either case.
 
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