Car Power Filter EMI Noise Ground Loop Isolator Suppressor for Auto Stereo Audio Radio Stereos Amplifier Amp Speaker Equalizer Subwoofer 12V

I don’t know how it works, but it does. I run a mini pre-amp thru my boat stereo to use with a CB style mic as an inexpensive PA system. (Guided sightseeing charter boat). New boat had a ton of line noise when the engine was running. So much, the PA was not usable. I ran the 12v supply for the stereo and pre-amp thru this isolator, and it greatly reduced the noise. There is still some noise, but it went from un-usable to useable. To be fair to the remaining line noise, I have to crank the radio volume to 33-35 so my guests can hear me. That’s pretty high, and I don’t fault this product for not removing 100% at the highest volume. Oh, like others have said, the wire insulation is ridiculously thick, but the wires are maybe 14 gauge, and appear tinned. The thick insulation only makes butt connectors really tight.

This absolutely works if installed correctly. Most of the Dual Electronics stereos have an alternator whine due to cheap or non-existent shielding within the radio itself. This is from my own personal experience with the brand. If your old car stereo did not have an alternator whine, and now it does, and you’re sure it the new stereo was installed correctly, it’s more than likely the build quality of the radio. To completely fix the whining noise, do the following: connect the Power Filter on the yellow, constant-hot (memory) wire between the vehicles harness and the car stereo. The “input” wire connects to the vehicle’s harness, the “output” wire connects to the stereo harness. Ground the black wire to a metal component attached to the vehicle’s frame. ZERO noise is now coming through my speakers when the truck is running. No noise on Bluetooth, AUX, radio, etc. Excellent product!

Updated Review 08/27/25: After it was installed in the car two to three weeks, it failed and would blow the car radio fuse instantly. I checked all wiring connections to make sure nothing had come loose. Once I removed this device, the fuse stopped blowing. I recommend not purchasing this item. My original update is below. I installed this in my 1999 Plymouth Prowler after replacing the factory radio with an aftermarket unit. Immediately after the radio swap, I noticed a distinct buzzing sound from the speakers that varied with the engine's RPMs, a classic sign of alternator whine. I was frustrated and worried I'd have to live with the noise, but then I installed this product. The difference was night and day. The alternator buzz completely vanished, leaving me with clear, clean audio. This device was easy to install and it completely solved my problem. Highly recommend it to anyone dealing with similar audio issues after a stereo upgrade."

The thickness of the insulation is annoying as it makes cleanly adding a connector to it impossible. The internals are not great. Someone did a very poor job with the soldering inside. It also relies on the thickness of the insulation to keep the components from shorting out on the case. The good: it mostly works. As the title says it took away like 80% of the noise. It's not perfect but I have to turn the radio up so loud that if it was playing anything I would never hear the static over what was playing. Really dont like how cheaply it is made. Hope it lasts.

I recently got into big audio with the DSR one it has 258 bands I believe so when I first installed it, it had a really bad alternator. I could hear my fans from every point of the car outside and interior lights you could hear just a whole slew of electricity problems The minute I installed this and turned my car on it went away. I mean you can hear and I mean to the slightest a bit of alternator wine, but it’s not enough if you’re not focused like you really gotta focus on it, but although this thing worked as it was intended. I love it. I would recommend this to anybody that is having car electricity noise problems

I was having a very audible static noise in my boat, I replaced every cable, wire, etc I could think of with no luck. I didn’t want to isolate a battery to solely power the radio so opted to try this. The static is slightly down but not completely gone. Overall, it did quiet it down but didn’t fix my issue.

Removed the whining static from the aftermarket install.

No matter what configuration I used, the radio stayed on. I have a 03 GMC Yukon denali. I wired it with direct connections from ground to battery/accessory to using the harness adapter from vehicle and the radio still would not turn off after vehicle was turned off. No fix.