horrible computer noise through speakers

natedawgg · 02-16-2009, 12:05 PM

hey guys, i posted this question over in the car audio forum, but never really got any good responses. the problem that i am having is that i am getting some major buzz coming from the computer through my sound system. it is not very noticable while driving down the freeway, but once you stop at a light and you have a slow spot in a song, it is VERY noticeable. there is a quick hand drawn diagram located in this post. i have tried many sound isolators, but they don't actually help kill the noise. any help would be greatly appreciated

Machinehead · 02-16-2009, 12:27 PM

I would think it's either the double amping or that Griffin imic.

onepuff · 02-16-2009, 12:31 PM

Did you try taking the griffin iMic out of the equation. I didn't read through the other thread so maybe you tried that already. Seems really strange to be picking up sounds from the computer.

natedawgg · 02-16-2009, 06:03 PM

Quote: Originally Posted by onepuff

Did you try taking the griffin iMic out of the equation. I didn't read through the other thread so maybe you tried that already. Seems really strange to be picking up sounds from the computer.

it is def not the imic. if i elimnate that the sound is MUCH worse. it could be the double amping, but that is my only option. the monsoon amp is factory and cannot be removed, without the smaller amp, there is not enough power to run the monsoon (it is a high level amp taking a speaker level signal), the mini's sound card or the imic's. i tried rerouting all of the speaker wire as far away from the power wires as i could. it helped a little, but not enough. i can't imagine that it would be a problem with the mini's chassis not being grounded (read on some of the other pc threads where it is suggested to run a ground wire to the frame of the pc). even if it wasn't i wouldn't know how to ground the chassis of the mini since it is mostly plastic anyway. i really am at a loss here.

golfguy · 02-16-2009, 08:06 PM

Why do you use the iMic instead of a direct feed off the headphone jack? Have you tried the headphone jack with a ground loop isolator? That really helped my alternator noise.

natedawgg · 02-16-2009, 09:20 PM

yeah i actually did try that, the problem is that this is not alternator noise. i did have alternator noise at first, i then put a in-line ground loop isolator in between the p1900 and the battery. that eliminated the alternator noise. This is actual noise from inside the mini. you can hear the hard drive, even the mouse move (actually i assume you are hearing the processor usage to calculate and display the mouse position).

One note, i did hook the system up to my iphone and play music through that and in that scenario there was no noise whatsoever. i believe that eliminates the signal crossover to the speaker wire, as well as the double amp.

thanks again everybody for all of your help

golfguy · 02-16-2009, 09:45 PM

OK, I know what you're talking about and I can hear it very faintly when my car is not running and the music is quiet. You're picking up the computer clock signal that runs the CPU. I don't know how you've got your Mini mounted, but you need to try to shield your wiring from the computer. Are any of the wires lying across the computer? Are they in close contact? Try using a sheet of metal to separate the wiring from the machine and see if it makes any difference. That may end up being a difficult problem to solve completely. Experiment with different mounting orientations and see if any of them is better. Good luck.

onepuff · 02-16-2009, 09:51 PM

Quote: Originally Posted by natedawgg

yeah i actually did try that, the problem is that this is not alternator noise. i did have alternator noise at first, i then put a in-line ground loop isolator in between the p1900 and the battery. that eliminated the alternator noise. This is actual noise from inside the mini. you can hear the hard drive, even the mouse move (actually i assume you are hearing the processor usage to calculate and display the mouse position).

One note, i did hook the system up to my iphone and play music through that and in that scenario there was no noise whatsoever. i believe that eliminates the signal crossover to the speaker wire, as well as the double amp.

thanks again everybody for all of your help

I don't think there are any moving parts in the iPhone so that may not really be helping diagnose the problem. Do you have any pics of your setup? Might help us see what may be the issue.

natedawgg · 02-16-2009, 10:16 PM

Quote: Originally Posted by golfguy

OK, I know what you're talking about and I can hear it very faintly when my car is not running and the music is quiet. You're picking up the computer clock signal that runs the CPU. I don't know how you've got your Mini mounted, but you need to try to shield your wiring from the computer. Are any of the wires lying across the computer? Are they in close contact? Try using a sheet of metal to separate the wiring from the machine and see if it makes any difference. That may end up being a difficult problem to solve completely. Experiment with different mounting orientations and see if any of them is better. Good luck.

ok so that is a possibility. the mini is in the glovebox along with the p1900. so there is very little space between the two. i have done my best to route everything from anything that has to do with power. the cables are really close to the machine, but i have tried moving the mini out of the glove box where all the cables are streched out (away from the mini). all to no avail. it is possible though there is something that i am missing. i am sure there is something somewhere laying or crossing over something.

onepuff: i don't have any pictures as of yet, but give a bit and i will try and get some. as far as there not being any moving parts, i didn't think about that. i was thinking more down the lines of the iphone is self powered and not relying on the cars power system. i don't know you are prob right though

Bugbyte · 02-16-2009, 10:27 PM

You are definitely picking up electrical signals from inside the Mini.

If you are using an iMic, then the signal is digital all the way down to the iMic connection. Try using a USB extension cable out of the back of the Mini and a short and well shielded (i.e. high quality) 1/8 cable to the amp, well away from the Mini.

natedawgg · 02-16-2009, 10:31 PM

Quote: Originally Posted by Bugbyte

You are definitely picking up electrical signals from inside the Mini.

If you are using an iMic, then the signal is digital all the way down to the iMic connection. Try using a USB extension cable out of the back of the Mini and a short and well shielded (i.e. high quality) 1/8 cable to the amp, well away from the Mini.

that is a good suggestion. i did try using a usb extension cable to get the imic away from the mini. however i am using a somewhat long 1/8 to rca cable. this did not help at all, but i may try getting a higher quality 1/8 cable however this all turns out

natedawgg · 02-17-2009, 11:07 AM

ok here are some pics of my setup. sorry if the quality is poor, i took these with my iphone this morning before work.

onepuff · 02-17-2009, 01:43 PM

Well i would try isolating the mini from the carnetix. Also have you just plugged in a set of headphones to the iMic output to see if that eliminates the noise. Just try to rule out each element one at a time.

Bugbyte · 02-17-2009, 02:12 PM

Well, there's your problem! PSU too close to Mini. Move it far away.

natedawgg · 02-17-2009, 02:25 PM

hmm very interesting. i will have to try that tonight. i have pulled my mini out of the glovebox while it was running, with no difference, but maybe if i pull the psu out and mount it somewhere far awayfrom all the sound cables that might be the key. Thanks

onepuff: that is a very good idea. i will try that as well

one more question. do you think all the components should share the same ground?

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