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."

Installing this device inline on the 12V+ power supply wire for my head unit eliminated about 75% of the whining noise in my Toyota Sequoia. I used to hear the whining noise from 1800-2200 rpm, now I hear it only between 2100-2200 rpm and it is not as loud. My vehicle has a 270 amp alternator, so perhaps this product is insufficient for that level of power. Well worth the money for this product, but I was a bit disappointed that this device was not 100% effective.

Couldn’t get rid of a loud whine/electrical noise coming through the speakers when turning on the bilge pump or nav lights in a boat. Tied this in to the electric for the radio and problem solved

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.

I was getting ridiculous engine noise and was at the point of purchasing a new deck but thought I would give this device a try before that decision. The install took me all of 15 minutes and the sound quality improved 100%. By far the best $15 I’ve spent in a very long time‼️💪💪

I bought this a wile back and just had time to install it in my 2011 Nissan Cube and all I can say is WoW it works extremely good I am so happy to not here are the annoying alternator wine any longer 🙀 wen I bought it I got 2 of them one just so I had a spare if needed 😹but yes I will give this a 10 ⭐️ if there was 10 to mark but if you have alternators whining like I did I strongly recommend this product!

Worked perfectly for my cheap Amazon CarPlay stereo. Had horrible alternator frequency being picked up, installed this and they went away.

Pointless, Did not work at all.

This filter did not work at all. Also, the metal case should not be grounded to any metal on the vehicle. Tried and blew the fuse instantly. Out of return window or I would have sent it back.

The whine in the speakers was killing the music, found this and decided to give it a go, worked as intended, no more whine from speakers at all, toyota owners will appreciate this filter

easy to install. worked as it should