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Right so somewhere in my set up is something that is picking up loads of electrical/radio interference and sending it to my monitors. The more computers that are on in the house the louder it is. When the guy in the room next me has his computer on it's amplified to the point it's picking up when I scroll the mouse and making a weird whoosh sound. It get's louder and louder in the evening until at about 2am I start picking up what sounds like a numbers station (this happens about 4 nights a week) which is great but also really irritating. Any ideas on what this is and how I can fix it? Do I live in a spy base? I think it's my iMac. |
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it's the wires. i recommend you get rid of them. |
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I've tried with different cables, 1/4" jack and XLR leads with multiples of each. The only ones that remain the same are the power leads and the USB lead for my sound card. I don't get the noise at any time other than when everything is plugged in to the mac via sound card so I'm guessing it might be the sound card. |
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i lived in a shit house near a radio tower and i had this problem too. i'm not sure if it was the tower, or just the house being crap, but the electrics picked up all sorts of fings. i drove myself crazy trying to eliminate it. eventually i just moved, and i haven't had the problem at all in the new place (which is not crap; not near a radio tower). so i guess my advice is that you move your "set up" to somewhere less crap |
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p.s. keep power lines away from audio lines, avoid coiling wires (which are already as short as possible, yes?) dunno if some sort of power filtering like a UPS would help |
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Yeah I can see some sort of transmission tower from my window. I've just moved closer to it and further up a hill, it's on the next hill over, the signal must be quite strong here. It's sticking up from amongst a forest, I wonder if I can go and have a look. |
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Do you live on Endor? |
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get shielded cables and make sure your audio cables and power cables are placed as far apart as they can, and only intersect at right angles. |
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oh, it also could be a grounding issue, as you said it only seems to happen when your imac is plugged in. try running it all with the imac ungrounded (get one of those lil 2-prong to 3-prong converters) - sometimes if your amp and your source have opposite polarities you can get nasty noise like you're describing (going along with scrolling and such). if it turns out that's the case, they you'll sadly either have to run your source or amp ungrounded, which isn't recommended, or get an amp with the correct polarity. |
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My first guess was grounding, the electrics in this house are dodgy as fuck. I just found out it is definitely the sound card. Getting an adaptor and plugging the speakers directly in to the mac produces no noise. Gutted as I can't afford a new one at the moment. |
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is your sound card usb? if so, are you using one of those fat usb cables with an |
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If it is a USB soundcard you could try splicing into a USB cable (make your own adapter) and supply a clean +5V from a power supply with stacks of decoupling caps (both large electrolytics and small ceramics for HF). Electro-magnetic interference tends to fall into two broad categories; conducted and radiated. Radiated interference will be from mobile phones (the bub bub bub bub sound with GSM texts and calls) and that sort of thing. Any nearby base station or tower will blast out tons of power compared to handsets. The power level is inversely proportional to the square of the distance so moving things further away from interference sources can have a big effect a far away tower is prob less than a nearby phone. Conducted interference travels up and down cables so the way to cure it is to disconnect the cable! This might include ground loops, which are sometimes easy to sort out on computers (unplug charger and use battery). Often ferrite is used on cables to help reduce radio frequency interference. Computers have all sorts of fast switching digital circuits which can cause all manner of burbling screaming sounds which can change with mouse movements and all sorts. The reason for this is that the CPU and RAM, etc is run synchronously so on every clock tick millions of transistors fire at once and cause a power surge on the voltage supply. This slightly modulates the amplitude of the voltage (think amplitude modulation like MW radio). If you're running a soundcard off an internal supply from the computer (or via USB) then the soundcard needs very well decoupled and cleaned supplies to avoid this being demodulated as an audio tone. General good tips: cross cables at 90 degrees to avoid inductive coupling (think like windings in a transformer). Don't coil wires (inductor again). Try to keep digital (USB, etc) away from analogue audio and mains leads. Use balanced audio leads and ground lifts where possible (keep mains earths connected or you may die if fault occurs). Use screened cables whe |
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...where possible. LOL |
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yeah, what he said... |
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I changed the usb lead and moved the sound card away from the iMac and my external hard drive as much as possible. Noise is a lot better but still gets MUCH louder in the middle of the night and picks up the number station type noises. |
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The weird noises started early tonight so I did a recording on my phone. |
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I don't know what they are and it's annoying when things like that happen but by itself it sounds ok! |
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It's quite charming I think. It certainly has character and it only happens for 15-20 minutes a night. I'm growing fond of it! |
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your computer sounds sad |
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havent read the whole thread and im sure you know allot of this. but here i go.. very important = make sure in your audio control panel on your imac that the microphone fader is set off and all faders are down except the heaphone/ or iine out that your using. i had a simlar problem and it was the mic input ( even though i did not have a mic connected.) if you plug in your headphones to the imac and the interference is not in the headphones , its not your imac. i presume your using unbalanced outs so you need to be sure your level out from the imac is set as high as possible without cliping. ( could test this with a sine wave recorded at 0 db so to match your imac out to amp) if noise/interference is still there? i would then take the same cable your using and connect it to a cd player or ipod or other sound card and listen to see if the interference is there. change your cable short as possible with good shielding. still there? = its your amp, make sure your connected to a line input on the amp. with unbalanced, level matching is very important for lowering noise/interference. |
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btw. I was presuming your using a stereo mini jack from the imac to (L+R) phono's or jacks. But if your using a sound card with phono or jack out (unbalanced) then most of what i said still applies. good luck : ) |
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That was complete bollocks freqy. Please don't give advice. Excited kids may come here and you are making it really difficult for them. |
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no it wasnt, you just want to hurt as usual. |
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