Page 1 of 2 12 LastLast
Results 1 to 10 of 11

Thread: Curing Audio Buzzing ?

  1. #1
    Constant Bitrate
    Join Date
    Jan 2006
    Location
    Dublin, Ireland
    Posts
    125

    Curing Audio Buzzing ?

    Hi all,

    I'm stuck and need advice please.

    I am attempting to install a CarPC (running Ride Runner) on an old Atom Thin Client PC (Dell FX160), with an SSD. I took out the factory Bimmer HU and got a mini 12v AMP on eBay, which has a 3.5mm and RCA inputs and the speakers are connected into the clips
    .
    I have removed the PSU from the PC and connected 12v straight onto the motherboard connection.

    If I connect earphones to the PC or if I connect my Android phone to the Amp Input, in both instances, everything is squeaky clean. However, if I interconnect the PC to the Amp over 3.5mm, with the keyswitch on but the engine off, I get a gentle tumping sound about once every two seconds. With the engine running, the buzzing then starts up. Music generally starts to drown it out but I issue will be if I use the car but decide not to have any audio running.

    Both devices are running off the same power source, which was a tap off the Cigarette Lighter. So really, the noise only comes when both devices are interconnected. I have a Ground Loop isolator which helped slightly but I'm at a loss to understand the source of the noise, particularly when the ignition is on but with the engine not running.

  2. #2
    Maximum Bitrate
    Join Date
    May 2012
    Location
    Grandville, MI
    Posts
    631
    Run wiring directly to the battery and see if that helps.

    It is likely that your cigarette lighter is not going to have large enough wiring to support your computer and your amplifier.

    You can also check the voltage at your devices and insure you are pulling full voltage at the devices when they are running but I am guessing that the small gauge wire that normally supplies your cigarette lighter you are far under powered to run your amplifier and computer.

    If you are running either the amplifier or the computer directly off automotive 12volts you need to make sure they are rated for automotive voltage because automotive voltages are ~ 12.5 volts with ignition off and ~13.5-14.5 with it running with spikes over 20 volts.

  3. #3
    Constant Bitrate
    Join Date
    Jan 2006
    Location
    Dublin, Ireland
    Posts
    125
    Thanks for the reply. I chose the cigarette lighter link because the cable is quite large, much more than any others and I think the cigarette lighter circuit is on a 20amp fuse which should be buckets for the PC (about 5A) and the Amp which I reckon is really quite low.

    The other thing that just occurred to me is that the PC is connected to a DC-DC step down converter (like this one below) whereas the Amp isn't.

    I wonder could it help to fit another of these to the Amp feed ?

  4. #4
    Maximum Bitrate Mickz's Avatar
    Join Date
    Sep 2009
    Location
    Australia
    Posts
    835
    There are two other things that need to be done correctly to eliminate noise induction into interconnect cables and further reduce ground potential effects.

    1: Use heavy duty double shielded audio leads between the PC and AMP. Ground loop isolators in the Audio leads compromise LF response.
    2: Run a very heavy gauge (6G) earth cable between the PC ground (case) and AMP ground (case).

    As has been stated, run the power from the battery and use very heavy cable if possible - It's not just about current capacity, it's about reducing inverter and digital noise that develops across the supply leads and therefor raises the noise ground potential of the PC and AMP. Thicker cable also takes the PC and AMP 12v supply closer to one of the biggest vehicle noise reducing capacitors you can get - the vehicle battery.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
    8" 16:9 TRANSFLECTIVE, Win8-64, Dual GPS RX and Garmin PC + Odyssey Nav, FM-DAB+, BB-Rec
    T-Screen HVAC control, custom microcontrollers, code and FE. CarPC Project

  5. #5
    Constant Bitrate
    Join Date
    Jan 2006
    Location
    Dublin, Ireland
    Posts
    125
    I have a Bimmer E46 so the Battery is in the boot (trunk) but I could tap off the connection under the bonnet (hood). What gauge of wire should I be looking to use for the positive 12v + ?

    The Amp connector is like this which isn't great for attaching a really thick wire


    The PC connection is a standard 4 pin ATX +12 volt power cable so that will be easy enough to do


    I have a feeling that the Amp is the real problem since I connected a USB Powered Bluetooth to 3.5mm adapter to the amp (Instead of connecting the PC) and got the same noise issues.
    Last edited by championc; 09-11-2014 at 05:23 AM.

  6. #6
    Maximum Bitrate Mickz's Avatar
    Join Date
    Sep 2009
    Location
    Australia
    Posts
    835
    Not familiar with it. If vehicle battery in the trunk, where are the AMP and PC located - how far apart are the two.

    Ideally run a +12v AND a Negative cable directly from the main battery terminals, again from a noise perspective both should be the same size and as heavy as you can get within reason, 4G cable would be good and cover normal future changes unless you go big power. Type of fuse is important and especially with high current cable, a suitably sized fuse should be fitted as close as possible to the battery in case of a short or importantly a vehicle Accident.

    However before going to the expense and trouble, I'd try good thick high quality audio cables from the PC to AMP along with a heavy earth connection between the two, it may be all you need in some cases. You should try earthing the PC and AMP to the vehicle chassis with very thick cable in case you haven't already done so, most times helps, occasionally makes it worse.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
    8" 16:9 TRANSFLECTIVE, Win8-64, Dual GPS RX and Garmin PC + Odyssey Nav, FM-DAB+, BB-Rec
    T-Screen HVAC control, custom microcontrollers, code and FE. CarPC Project

  7. #7
    Maximum Bitrate
    Join Date
    May 2012
    Location
    Grandville, MI
    Posts
    631
    To add to what Mickz is saying, If you create your own audio cable use a twisted pair to run the audio between computer and amplifier. A twisted wire that is shielded is the best solution but a twisted non shielded wire is still better than a coaxial type wire.

    I have heard very expensive coaxial wires on the same system as one that had a couple 14 gauge stranded wire twisted with a drill. The cheap twisted wire was much clearer and carried less noise. The idea is that the twisted wire will allow the noise to be cancelled out because it is carried by both wires.

    I 100% agree otherwise with everything Mickz says. Large wires directly to the battery.

    In my vehicle I only have a PC and I run an 8 gauge wire to the PC.

    Rodney

  8. #8
    Constant Bitrate
    Join Date
    Jan 2006
    Location
    Dublin, Ireland
    Posts
    125
    Thanks for all of this. The Amp is under the front Ashtray and the PC is in the glovebox, so both up the front of the car. The Bimmers have a Jump start + point in the engine bay so that would be the point for me to connect to. I have some pretty thick multistrand home audio loudspeaker cable (Like QED 79) which I could use for the earthing.

    Can I make my own twisted pair cable from Cat5/6 cable ?
    Last edited by championc; 09-11-2014 at 07:07 AM.

  9. #9
    Constant Bitrate eugenweij's Avatar
    Join Date
    Aug 2010
    Location
    Rozenburg, Netherlands
    Posts
    216
    cat 5e consists of 4 twisted pairs so I guess you can use it , just make sure you use a pair when wiring things up
    View my worklog here

  10. #10
    Maximum Bitrate
    Join Date
    May 2012
    Location
    Grandville, MI
    Posts
    631
    Cat 5e wire should be OK but may not be twisted tight enough. If you try it and it doesn't work well try twisting your own 22 or 20 gauge pair for each side. You can do 4 channels of sound with Cat 5e wire. Make sure you use stranded wire and not solid wire. It comes in both "flavors" I HAD mine setup with Cat 5e wire and if you look at the "$3 aux input" thread they suggest using cat 5e wire...

    Just make sure as already said you use a pair that is twisted together for each audio channel.

    Your power wires should be at a minimum 10 gauge to the battery to insure your wires are sufficient. No such thing as over kill here... Overkill is "just enough".
    12 gauge MIGHT work but I would suggest minimum of 10.

    Rodney

Page 1 of 2 12 LastLast

Similar Threads

  1. Buzzing in audio!!
    By joe_c in forum Car Audio
    Replies: 5
    Last Post: 12-22-2006, 02:02 PM
  2. Fiberglass Curing Question
    By Curry in forum Fabrication
    Replies: 3
    Last Post: 08-28-2006, 08:11 PM
  3. Can this get rid of the buzzing?
    By meyer64 in forum Car Audio
    Replies: 4
    Last Post: 01-21-2005, 10:26 AM
  4. How do i get rid of the BUZZING!!
    By paintballgod in forum Newbie
    Replies: 24
    Last Post: 01-07-2005, 03:42 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •