Help with a ground loop problem?? - Page 2

ReAX · #16 (**permalink**) 07-02-2009, 01:43 PM

just to verify it before you learn to dismantle your dash, get a DMM. VDC, and put one probe on the amp's ground and the other on a good ground on the firewall. With everything running, if you have a ground loop you should see 0.1v or more. If it's less than 0.1v, the connection is adequate between the two points and you don't need to share the ground.

Karl4Cat · #17 (**permalink**) 07-02-2009, 02:01 PM

.255 mv is the reading I get.

Karl4Cat · #18 (**permalink**) 07-02-2009, 02:05 PM

PS You guys have any idea why the ground loop isolator cut the output so much? I've used them in the past as a quick fix with no issues.

ReAX · #19 (**permalink**) 07-02-2009, 03:28 PM

They are a band aid product. The band aid usually includes components that smooth out the voltage/current going through it. Which is nice if you want DC power that fairly consistent, but the audio is highly variable AC.

I want to say they use an inductor in them, which smooths out the current and has an impedance. It's like connecting speakers in series, your adding the resistance together to give a higher total resistance on the amp.

AudioNutz · #20 (**permalink**) 07-02-2009, 03:30 PM

Not to mention, they never work. They just cut the output down so you can't hear the noise, in hopes that you won't notice the cut in signal.

Karl4Cat · #21 (**permalink**) 07-02-2009, 06:59 PM

Well, problem solved. I took the easy way and tried a different brand of isolator made by PAC. Perfect! No signal and frequency loss like the Radio Shack model. I actually googled the problem and found others said the same about the Shack ones. So, I went to a local shop and presto fixo. What an outstanding addition to the factory sub (the Bazooka) without blowing too much coin. Thanks for the info guys. I'm glad I didn't have to use it all and dig further...