Car Power Filter EMI Noise Ground Loop Isolator Suppressor

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.

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 have a velex bluetooth amp that I bought from amazon 3 years ago. I isolated the static to the unit and I'm pretty sure it might be going bad. This is in a 1970 Monte Carlo. I figured I'd try this before placing the unit as I know its cheap and probably wouldn't last long. (3 years is good compared to others reviews of the unit). Surprisingly this removed 90% of the static, maybe more. Hoping it will help me limp along a while longer without replacing the unit. I can't hear any noise at all any more, maybe a crackle once in a while but before I installed this line filter it was unusable. Very pleased!

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 product was installed in a professional manner, and there was 0% accomplished with RFI elimination. Altenator/engine whine and static are present directly after installation. I mean the filter as advertised seems well built, out of metal and not plastic, thick insulation on the wires which is good. And yes as stated, it was installed in a professional manner.

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