Buzzing noise help

fletcher5555 · 05-24-2005, 03:26 PM

OK guys now i really need help with this one. I have my Car PC hooked up under my passenger seat which is being powered offa 240 volt inverter. Now I bought a Amplified Graphic equaliser to help me power my front and rear speakers so I install it and have a buzzing noise coming through the speakers. I check all the wiring which is OK and so swap the input from my computer to my little mp3 player and the buzzing is gone.
What I do next is power my pc off the Mains from my house (thanks to an extension lead) and the buzzing again disapears so it seems like the noise is occuring somewhere between the inverter and the step down transformer that comes with the pc. Does anybody ahve any ideas what I can do to get rid of the buzzing? I have no idea how the equalizer is picking the buzzing noise up as the amps and subs work perfectly its just the amplified equalizer powering doorcard spekaers which is buzzing. Now im Very experienced in electronics and a friend of mine is a MASTER TECHNICIAN for ford and we still cant find a way around it other than trying a new inverter. Any hekp would be much appreiciated plus you would get the bonus of saying you know more than the Head mechanics at Ford motor company. Thanks in advance for your help!

stevieg · 05-24-2005, 03:47 PM

Try a ground loop isolator.

Also, check your ground is good. Common error is the power ground being a worse ground than the RCAs' sheilding, hence that's used for ground which equals noise.

In addition, inverters tend to introduce a 50hz noise to the power (square sine wave for AC instead of analogue curve) which CAN be OK if you don't have ground problems or EFI issues.

First port of call is ground loop isolator.A multimeter is also invaluable to check the resitance to ground on all your paths to ground so you can make sure the power supply ground is the lowest resistance.

stevieg · 05-24-2005, 03:48 PM

Oh, just saw you're in birmingham. I'm there every day

Took my car into Bristol street half way through the last build if he works there he might have seen it

fletcher5555 · 05-24-2005, 04:44 PM

STEVIE G no way my mate works in Wolverhampton and I will check my ground but im pretty sure its good. The funny thing about it all is that if I hook up the pc straight to my mains at home the buzzing goes which leads me to believe its an inverter problem. More investigations tonight after work anyways!

fletcher5555 · 05-26-2005, 10:09 AM

Hey guys im still needing more help. I still cant get rid of the buzzing noise and its doing my head right in now so im geting desperate! The buzzing does not come on when the car is powerd from the mains from my house and dosnt come on if the input ISNT the car pc but a external mp3 player. I checked my grounds and they seem fine and i tried another inverter yesterday and that did the same thing. Due to the power cable being that of the Sumicomm/Xenarc/IWill Case Power Cable mother boards its really hard to find another powerin alternative apart from the carnetix box which i bought but was faulty so dont really wanna use them again. Any otehr thoughts? Maybe a filter that will get rrid of the sound for me or a alternative power source or ANYTHIN????

ErikArmbrust · 05-26-2005, 10:19 AM

You know..... you could seriously wrap your little speaker amplifier box that has the buzzing in foil and it should get rid of all of the EMI that could possibly be generated around the car. If you just ground it though, it would get rid of it. Try running a wire from the metal casing of the amplifier to your chassis. That should do it.

fletcher5555 · 05-26-2005, 10:22 AM

Sorry dude I htink I need to elaborate more. The amplified graphic equaliser which is powering the doorcard speakers makes them buzz when I connect it to the car Pc but not when i connect it to my external mp3 player. Everthin is grounded ok else surely I would still get same buzzing sound when I hooked up the portable Mp3 player

emdzey01 · 05-26-2005, 01:11 PM

what kind of setup are you running on? i used to run an inverter setup through my shuttle pc, and the buzzing came from my power supply. whenever it ran on the inverter the buzzing was there, but when i plug it in my house the buzzing stopped. changed my power supply (still ac-dc) and the problem was solved.

fletcher5555 · 05-27-2005, 02:33 AM

What do you mean changed your power supply did you get a new inverter?? Cheers
Fletch

stevieg · 05-27-2005, 05:32 AM

It definately sounds like a grounding issue.

Try plugging some headphones into the line-out socket when it's powered from the invertor and see if you get the buzzing.

fletcher5555 · 05-27-2005, 06:06 AM

I will check that mate. I have bought a audio surpressor which what DJ's use appently which is supposed to filter out every noise apart from that of music which I should recive by today so Im gunna give that a try also. I was doin so well till this problem! All I need to do is get rid of this noise properly mount the Graphic and the install is complete!

emdzey01 · 05-27-2005, 07:05 AM

try changing your power supply. maybe even switch to opus dc-dc so you can throw away your inverter too. if the buzzing stops when you plug it in your house that most likely is an electrical/grounding issue, not the sound card.

stevieg · 05-27-2005, 07:52 AM

Quote: Originally Posted by fletcher5555

I will check that mate. I have bought a audio surpressor which what DJ's use appently which is supposed to filter out every noise apart from that of music which I should recive by today so Im gunna give that a try also. I was doin so well till this problem! All I need to do is get rid of this noise properly mount the Graphic and the install is complete!

Try a ground loop isolator. The suppressors commonly go on the power connections, and most will not support a big load.

As some of the others say, have you looked at a DC-DC PSU that's actually built for in car use? It's a lot more efficient than using an invertor and if your hardware is suitable for it will make your life a lot easier. I remember when I used an invertor a few years ago and it was a PITA (this was before you could buy shutdown control for them) and I would NEVER go back to using an invertor even if you paid me.

Edit: this is probably my last post in this thread, as we seems to be all telling you the same answer to your SIMPLE problem again and again.

neon_eddy · 05-27-2005, 08:13 AM

yes I second the motion, once you go DC you'll never go back.. biult in startup shutdown controller, small foot print, etc..

I still have an inverter for other things I use fromt iem to time.. but there is no reason to purposly introduce a 60hz buzz on the system.. I also use mutiple grounds, keep grounding till it stops..

I made my own ground loop isolater for about $10 from radio shack parts.. they have mono channel isolators.. just buy 2 and there ya go.. since going to cd I have not needed it though.. dumping my head unit helped too..

DRWeside · 05-27-2005, 08:27 AM

Make sure your power supply is grounded. I had the same problem and the fix was running a short lead from my ground distribution block to the neutral(?) prong on the PS's power cable. I never tried running the lead directly to the PS's case, but I guess it should work. The problem is that the inverter doesn't provide adequate neutral and ground circuitry.