Like Tree0Likes

OT: Help with Audio Problem...?

Old 11-20-2002, 08:56 PM
Thread Starter
Join Date: Nov 2000
Location: Westport, Kentucky
My Boats: Baja Force 235
Posts: 1,282
Default OT: Help with Audio Problem...?

I have a Sonic Impact A3D audio card, basically just a decent sound card in my computer. I am running RCA type cable to my home stereo amplifier inputs. The sound card is driven by an application called MusicMatch Jukebox, just an MP3 player. When the signal gets to the home stereo amplifier there is a 60 cycle hum. I tried feeding the amplifier with a handheld Sony walkman and the 60 cycle hum went away. I tried one other computer using a different type of sound card and the hum continues. If a laptop running on battery is used there is no hum. I have tried relocating the sound card lower in the case and placing a metal shield over it. Also unplugged all other device on the computers power circuit and tried plugging it into the same circuit as the amp to eliminate a ground loop.

Cable in use is RCA cable to COAX to RCA cable. Yes this is a goofy arrangement but for the distance and walls I have to pass through this is the only way. When I temporarily relocated the computer to the same room as the home system and ran a RCA cable that was only 20 feet long the hum was still there so itís not the cable.

Is there any device active or passive that can cut the 60 cycle out of the RCA cable? If I get this system rigged properly I may just put the laptop in the boat with and inverter. The interface for selecting and changing MP3ís on the computer is so much better. Bought a top of the line MP3/DVD changer and the remote has more buttons than a triple installation. What a pain! I would rather just use the computer.

Tim T.
BadDog is offline  
Reply With Quote
Old 11-20-2002, 09:12 PM
Turbojack's Avatar
Join Date: Sep 2001
Location: Houston, TX, USA
My Boats: 2003 Eliminator 30' Daytona
Posts: 2,285

When you plug the laptop in does the hum return? Have you tried an isolator? I'm not sure that would work.
Turbojack is offline  
Reply With Quote
Old 11-20-2002, 09:59 PM
Thread Starter
Join Date: Nov 2000
Location: Westport, Kentucky
My Boats: Baja Force 235
Posts: 1,282

Yes the noise returns when laptop is running on AC. Tried flipping the AC input cord on the amp and removing the ground wire on the computer. Removed shield on output end of audio cable. Looks like I need to run the computer off of a transformer?
BadDog is offline  
Reply With Quote
Old 11-21-2002, 01:12 AM
Donzi38ZX's Avatar
Join Date: Oct 2002
Location: Whiting, IN
Posts: 761

A couple suggestions to try:

Does your computer have two or three audio jack connectors? If three: one input for MIC and two outputs, one for headphone and one for line out. If you have a line out use that. Also plug in a set of headphones in the headphone jack (first disconnect from stereo) and see if you get the humming. Which input on the stereo are you using? How high is the volume set on the PC?

Donzi38ZX is offline  
Reply With Quote
Old 11-21-2002, 09:10 AM
Charter Member #232
Charter Member
Audiofn's Avatar
Join Date: Oct 2000
Location: Carlisle, MA USA
My Boats: 1979 Formula 302, 99 Formula 353, 81 Donzi 18 2+3 with 454
Posts: 18,379

The problem is the two units are developing a different groud plane and that is causing your hum. SO there are a few things you can do to probably eliminate the problem. First is if your laptop has a three prong plug then get one of those Three prong to two prong plug addaptors like you need if you life in a really old house. The other is to get a ground loope Isolator for the RCA's. You can also try cutting the ground shield on the RCA at the Stereo end of the RCA. That should also get rid of the hum. Hope that helps ya out. Chances are there is a problem with your computers moter board ground that is shoing itself with the hum.

Put your best foot forward!
Audiofn is offline  
Reply With Quote

Related Topics
Thread Starter
Last Post
General Boating Discussion
04-10-2006 07:25 AM
General Q & A
05-25-2005 02:26 PM
General Boating Discussion
05-24-2005 04:54 PM
General Q & A
12-05-2003 01:00 AM
General Boating Discussion
02-26-2002 01:07 AM

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -5. The time now is 03:59 PM.

Copyright 2011 OffShoreOnly. All rights reserved.