Hi Clive, the idea of the tin foil is to join the two transformer shields as one Faraday Shield. It may be that the same components/circuit are used with a plastic cover. This is normal for use in vehicles, due to air-born interference, like you said from the ignition high voltage spikes but the main use of this type of audio signal isolator in vehicles is to suppress the alternator electrical noise. It used to be worse in the bigger type cars due to the high output alternators used having to cope with the amount of electrical items such as Electric windows/Sunroofs, Air-con, Rear heated screens etc, all quite modern in the day. I used many of these in my days as an Auto-Electrician in the 80's on big audio amplifier systems. Great videos, keep it up. Many thanks

The foil is so the aliens can't listen to your music. ;)

So, I’m at Uni studying music production and have had whole 2-hour lectures on something you essentially explained in a 9 minute video... -_-

i bought one identical to that one from ebay. i just got it today, and it works perfect. the background noise disappeared. fantastic!

For those wondering. Car alternators can leak out small amount of AC voltage which can be picked up by RCA cables going to your amplifiers.

The foil was likely being used as a shield to block out hum/noise. It's a technique often used in guitar electronics where the cavities that house all the wiring/controls are lined with a conductive foil (usually copper) and then the foil is connected to ground. This makes it so that any electrical interference is picked up by the foil and sent straight to ground

These are great. I've used them in several projects. Most notably was my 80s Bluetooth boom box where I used it to eliminate the horrible noise the Bluetooth adapted was creating. None of the ones I took apart had that foil on top though but we're surrounded by a razor sharp piece of tin inside the outer cylinder.

The metal case is a special metal called a mu-metal. It really likes magnetic fields. It likes them so much it acts like a magnetic short circuit (low magnetic resistor). The aluminum foil on top of the transformers is used differently. Aluminum doesn't like magnetic fields, so fields are reflected away (high magnetic resistor). I don't know why they didn't mount the transformers 90 degrees from each other to prevent channel crosstalk.

I have installed one of these in my car and it works fantastically. Around the time of the install, I also made sure that I had all power and signal wires isolated and insulated. The combination of doing these two things completely rids the car of a static hum.

Thanks again for the vids Clive kept me entertained for a while today. I'm already looking forward to the next one.

I had a similar issue with my external USB-AMP (no ground Audinst HUD MX1) connected to my PC. I was soooo glad when I got one of these and it solved my issues. The AMP is also creating a very loud humming when the USB is not connected to the the PC but its power supply is connected to the mains. Thanks for showing us what is inside!

Using one of these in my car helped on eliminating very annoying interference noises from the alternator and the servo steering in my subwoofer amp. Awesome to have an explanation on how it works :3

Thank you so much for making this video, I bought 2 of these a couple weeks ago and I was wondering what was inside of them but I didn't want to take them apart and damage them.

They are magic in older car audio systems. I’m glad I found your video to explain how it works. It fixed the hat was going to cost me hundreds to fix and only cost $12 aud.

I used one of these to solve a very bad hum with a sub woofer, was doubtful it would work, but was pleasantly surprised to find it done the job perfectly.

A must have for car audio, too. Great for alternator whine and other issues. Quite often it's not practical to have all the equipment grounded to the same point (star ground) so there will be slight voltage differences in different chassis grounds. Also the signal wires will be a bit long from the dash to trunk mounted amplifiers, and often will have to run near other wiring and pickup noise. As you said, a great get out of jail free card to have in your box. There is super posh version of this where the audio signal is changed to light and run over fibre then converted back at the other end. Great when the cable has to run past very noisy equipment.

This also frequently happens in car audio setups where you'll get a high pitched hum at the same frequently as the alternator is rotating. It can end up being a completely overwhelming whine. And this little device fixes that perfectly as well.

i would say the foil is for magnetic shielding they probably make that internal piece and sell it to people who install it in cases that probably offers a slight bit of magnetic shielding when that same component is in a plastic case

Thanx for the tip for the Quicktester!

These are good for eliminating group loops when you are powering the source and amp off the same DC supply or battery. Very handy indeed.

Quite an old video this but the most common ground loop in a car that I've fixed more then once for friends with this very thing is alternator hum from an external audio source feeding the stereo. Like a phone being charged while plugged in through the auxiliary cord. This thing works every time.

Very elucidating video. Thank you!

A couple of years ago I was going to modify an old tube radio with an aux-in jack for my grandfather, but I eventually gave up on it because I learned that they operate on half-wave rectified mains voltage, and the plug was non-polar. So just by plugging it in the wrong way around, you could end up with live mains on the aux jack. This is exactly what I needed, and I think I might re-investigate doing that now.

These one are VERY helpful and was THE solution for a little project some months ago.... I had needed such one too to connect my Samsung galaxy S3 with an pam8403 DIGI amplifier board AND a power bank cell charger for cell phones at same time. (Power bank charger as power supply(5V) for the amp and for charging the Samsung S3 at same time.) WITHOUT the audio isolator transformer,i had cannot charge the S3 and powering the pam8403 amp at same time because of ground problems(weird noises and probably BAD for the digi amplifier).

I have a couple of these in my audio bag. Thanks for the great video.

These really are, as you say, a toolbox essential. I made my own, on the cheap and in a hurry, with two 1:1 (600 Ohm) fax modem transformers that I had lying around from old defunct kit. OK, I know it's the audiophiles will tell me how poor a solution this may be but in practice, to run sound files for a show, the little box worked a treat. I do however have two of the very same product featured in your tear down.

Great video! Thanks for explaining it so simply.

Different substations can be a massive issue even for mains electrical work (as you no doubt know!) let alone audio. I remember measuring 50ish amps flowing down the armour of an SWA. The voltage was tiny...

I usually end up buying stuff you show, but in this case I've already got a stack of these in use today to break open the earth loops between my 3 PC's, mixer and amp. They're very cheap and work well. Decent bandwidth if I remember right. They've been around for many years. I remember selling them in the electronics shop in Newington 15 years ago! ___________________________________ Maybe the foil was used to join the two transformer frames together to help with channel isolation?

I have an older Toshiba flat screen television that I'm using one of these devices on. Mine has some variable resistors built-in to adjust the volume. I had tapped in to the speaker outlet & send the signal to a stereo system built for computers. It is a nice unit made by Creative. it has a subwoofer box & two nice stereo speakers. I knew when I tapped into it, this was the only way it would work.

As an audio engineer I can tell you there will definitely be some frequency loss. The reason is the transformers are in effect "seen" by the source and amplifier as transducers, even if the impedance is very high. Like any single speaker, it can not reproduce (pass) the entire range of human hearing effectively. I tend to think it would loose a significant portion of high frequency because inductors in AC resist (impede) changes depending on the "Henry" rating of the coil and frequency of the varying AC waveform.

I bought two audio isolators ( rca + 3.5mm) after watching this video. This stuff works since for some reason my pc causes a hum and buzz whenever I run any games that utilizes my graphics card heavily. Thanks bigclive

I remember helping people fix "Noise issues" with their car audio systems back in the day. They always showed up with one of these devices, I never needed them, and the real issue was always one of 3 other issues... #1. Crappy ground connections, or grounding points at different points on the car that had high impedance between them. #2. Inferior or unshielded long RCA cable runs, that were ran next to a large, high current, power cable. #3. A shitty head unit, OR blown ground traces on the RCA output of the head unit or EQ, because someone carelessly let the end of their RCA come into contact with the B+ on their amplifier or somewhere else in the car. I'm in NO way saying that those noise isolaters are useless, they are very useful for mains powered equipment with ground loop issues, but they were very rarely needed in car stereo installations to cure noise issues.

Yeah I have one of these in my car for my CB Radio. Fixed my SWR problem.

Humbuckers or DI boxes are the two mainly used in the AV industry. Di boxes have switches on them so you can choose left right or stereo and earth lift. A bit more expensive than a humbucker, but more versatile.

I remember as a student having the revelationary information bestowed upon me of "not all earths are the same". This was 3 months in to a Physics degree, so the concept of "moving clocks run slow" (i.e. Special Relativity) was already taken as read, but the concept of the earth pin on one socket having a p.d. to the earth pin on a neighbouring socket seemed alien. As my uni had a strong musical tradition, the weird thing was that many/most of us had already experienced this when playing at the open mics and music societies, but like so many things in life few people (myself included) actually understood and hence tried to combat the noise, instead accepting it was just an artefact of the equipment.

Unbalanced audio connections can pretty much be considered broken these days. With computers, shielded network cables and all that good stuff in modern setups, there's earth connections coming in all over the place. You'll be catching a ground loop faster than you can say "ground loop". Ground loop isolators are handy when having to interface unbalanced to balanced. One system relies on floating ground, the other is earthed everywhere. The important thing about balanced connections is the balanced impedance part, actually (if in doubt, consider the case of no signal). The whole thing can be treated as a Wheatstone bridge. If shield currents cause audible noise, usually one component suffers from a faulty shield connection hookup known as a "Pin 1 Problem". AES48-2005 clearly states that the shield (XLR pin 1) *must* go to chassis directly and immediately, and must not connect to local audio ground first (the connection between both is made elsewhere). Now components that disagree should mostly have gone away by now, but it looks like even recent KRK Rokit speakers (5", 6" models at least) are still affected.

For a hi fi quality isolator for home / stage use I would recommend Omnitronic Lh-081. Should work ok in cars as well I guess but it may not as good as this one. The LH-081 frequencies range is 15Hz - 30KHz, input & output impendancies are 600Ohm.

Great explanation - thanks!

My thoughts on this: the metal casing's essential role is to provide a Faraday cage, meant to ensure that no RF interference can be caught up, then amplified. Given the car audio focus, you are right, the ignition would be the main culprit however other RF sources should not be ignored. After all, you cannot create a winding with the unscreened audio signal cable and hope for the best - that's how you end up with an antenna. The bit of foil between the transformers should serve to discharge any potential that could build up in-between.

I'm a sound designer, and I've decided I need about 500 of these

thx so much i have been looking for ever to fix it with out a RCA isolator thx so much

I used to rehearse in a shared practice room in the 80's, and somebody had put electrical tape around the ground pin on my bass amplifier mains plug. So we were playing along, I put my shoeless foot up on a radiator, and got a spectacular electrical shock. That's when I learned about the bad way of ground lifting. I also must have left the ground for a moment there too. Scary stuff.

we had to use these a lot during the 80's for car stereos. We would get a whine that changed with engine speed from the alternator.

in the pro audio live sound scene we use "DI" direct boxes where an instrument has an unbalanced out going to our balanced mixer board in. all they are are balancing transformers but they are electrically isolated. in the car audio world you can get alternator whine and noises of the like. its sometimes funny when using am radio and you have all this interference, usually in the cheaper made products.

Thank you for the tear down. The transformers in the Pyramid NS-20 are about a quarter of the size in the unit you have there. The NS-20 has a plastic clam shell design and has just a small piece of foil for shielding. Also , the transformers are wrapped with tape before the foil. So , the foil is just shielding in the NS-20.

so its just an 1:1 transformer, aka isolation transformer. and yes in car aftermarket audio systems you can have problems, sometimes the car alternator can leak some humm on wine to your audio signal. i love your channel😁

As a soundie myself, I am astounded at how many others I have seen who have pulled the cutting the mains pin trick to clean up ground loops. When I was an in-house guy in one venue, cables like that brought into the venue (usually by outside techs) would end up in the trash.

I used to work for a company, Road Radio way back in the 90's. I can't say I've ever come across one. We used to fit anything from Philips to Nakamichi audio systems, getting rid of audio noise used to involve cleaning all earthing points and soldering the wiring on the more elitist jobs. Sneaking one of those in to a system would have probably saved a lot of work lol. Thanks for the post.

I've seen some comparisons/measurements of these devices and there's definitely different levels of quality out there. To get good transformers with extended bass response you've typically got to get something beyond the common $10-$15 devices.

The foil links both grounds and therefore will provide a uniform ground voltage for reference for both left and right audio signal,

The problem in cars is that once you got audio signals from your radio to an external amp the return currents won't just flow through the chassis or the wire but also through the audio ground. The generator puts out a lot of ripple so you end up hearing your engine RPM times 3, 6 or even 12(depending on the generator) in the speakers. This is where the isolator comes in. It stops the ground current and ripple, so you won't hear the whistles in your speakers.

thanks for showing how they work,

I did a quick test with audio signal generator on one side and a scope on the other, and it looked fairly flat from the high range all the way down to 100Hz, where it started dropping off rapidly. Better than I expected for such small formers, but Altronics have a similar one that makes even better claims about the low end. At those frequencies, I doubt the audio would suffer much by just boosting the low end with the sub amp or EQ though.

The foil looks to me, bodge job :) Usualy, we always place pair of stereo trasformers 90 degree (eliminate magnetic crosstalk), then we connect the transformer shielding together (eliminate EMF noises) the outside shell is a simple raw steel, to block low frequency magnetic waves from the transformers core, because this transformers has a bit air gap. on consumer level, working perfectly. The best ones uses precision winding, hexacore coils, gold or silver plated shield, and some kind of special core. I even seen mixed E and toroid transformers. What I dont like about this transformers, is the way, how they destroy the high frequencies and the saturation. Use short strong rca cables, and for big distances, no other way, just balanced signals. And yepp, same source low resistance earthing. Or digital interconnect. Thank You for sharing :)

Love audio technical explanations. New subscriber. Kudos for your channel. (UKposts sent me from Mr. Carlson's Lab) Thanks

The foil is for electrostatic shielding. Some transformer, power transformers in older tube gear even, come with a shield between the primary and other windings. Normally you'd just ground it.

The situation where you have line noise on the audio line is called a ground loop. I use a direct box to connect my laptop to my main mix and amp to eliminate this situation but one of these little things will work also but it's intended use is in car audio environments.. Sure you can use them in home systems as a temporary fix but its best to get equipment all on the same circuit and have proper balancing when installing a home system. Commercial system are more versatile and are made to be moved about a lot so the "on stage" direct box is the answer to those problems. In car audio you get noise from the alternator, fuel pump and, onboard computers. The noise is more prominent through HF Ham radios and CB radios but those require a DC capacitive filters and not an audio transformer, Car audio amplifiers of the cheap breeds will need these transformer baluns in the input lines though. The foil on top looks like it may help with phase matching or the electromagnetic flux matching but it does not seem very effective since it only foil and not a metal shim.. It could be something like you said also to help keep interference out, there is just no real good way to tell. I mean it could be there because the foil tape matched the transformer casing. who knows..

great video thanks so much for the explainer :)

I have 2 of these in the bits box I do a lot of outdoor events some involve pluging in other peoples kit like cheap crappy radio mic receiver's mp3 players they work a treat.

I'm glad I'm not a car audio builder today. With all the external signals like can buses, wifi, Bluetooth, and radar equipment in vehicles today, it might be tough to get a clean audio signal. I recently turned up the volume on my wife's Honda CRV with all that equipment in it and on USB audio with no USB device installed, I heard all kinds of squeaks and buzzing, in the background. It also sounds like they have the high-end cut at a steep slope to filter noise also.😮

My guess is perhaps the foil was used to ground the outer case to the transformers provided the transformer shells are grounded to one of the audio cables.

Very well explained. I was really wondering what this thing does and whether it could solve my issue. Turns out it can, it's just a bit chonky. My guess is that the foil is for shielding. Like the equivalent of shielded cables but on the transformers. It should ensure that no noise can be picked up by the components. It might be an overkill since it is in a metal case already but you can never be too protected from RF interference

i was always taught(and please correct me if im wrong) but "balanced" audio was the act of running the same audio signal through two separate wires with one being "normal" and the other being polarity inverted, once combine they cancel out any noise... ---------------------------- In fact, a little bit of googling brought up this: www.ians-net.co.uk/articles/balanced_lines.php To remove noise from a signal we need some way of working out what is our wanted signal and what can be thrown away. Balanced lines achieve this by transmitting two versions of the signal down their length. The source equipment sends the normal signal down one conductor and a polarity-inverted signal down the other. This is usually done using either transformer-based or electronic output stages. The cable itself is designed with the conductors having very similar impedances and twisted along their length so that any noise is picked up equally by both conductors, no matter where in the cable it occurs. The receiving equipment has a transformer or electronic differential amplifier, and takes the inverted signal and returns it to it's correct polarity. At this point, the wanted signals on each conductor are both the same polarity, whereas any noise is of opposite polarity. Summing the signals from the two conductors together reinforces the wanted signal and cancels anything unwanted, leaving a recovered signal which is very close to the original. (this is known as Common Mode Rejection - i.e. any signal which is the same on both conductors is removed.) Even balanced lines aren't perfect, though - slight differences in impedance, twisting or input gain will allow some noise to slip through. This isn't generally a problem unless you're using very long runs or working in areas of high interference. It looks like the same as what twisted pair does with networking/telecoms...

The last time I used one of these was 15 years ago, and it was purchased from RadioShack. it was in my car, and it was sold as a 'ground loop isolator'. Interesting to see what is actually inside one of them.

as for putting one of these in a car, you get very bad audio wine from the alternator when the phono cables are routed alongside the amp power supply cable, very good bit of kit

good day I was wondering if the transformer used here is the same used on computer modem boards. I have a couple of modem boards collected over the years and was thinking of using the isolation transformers in there for such purpose. Nice video!

I was playing live one time and none of the equipment was mine I got up to do the first song and holy crap that mic shocked tf out of me the entire song

I made my own out of a super heavy mains filter, just removed the caps and fusing/filtering

I suspect the foil is to ensure a conductive path between the two metal can halves as it would be pressed against the interior of both cans when assembled. If they had soldered the two halves together then I doubt it would have been used. In car audio you are most likely to require filtering on the power input, especially to a radio, as there can be a lot of conducted common mode noise on a vehicle's power rail that can then get into the tuner (most decent amplifiers will/should have adequate input filtering of their own since they do not have the added task of functioning as a proper radio receiver where the vehicle chassis (ground plane) is also a part of the antenna path. Usually these filters are a simple inductor and one, or more, capacitors to help filter ignition and commutation noise from the power input.

The quality of the protective earth is not just a safety issue it greatly impacts ground loop formation which sends op amps wild.

The big power amps used in car audio suffer worse than you might expect, generally they contain big dc-dc converters, if you have a few of them you can often hear the beat frequency of the different oscillators as well as the other crap. I have previously used audio transformers from scrapped radio base stations to get round these earth loop problems. The transformers are used to interface the transmitters and receivers to leased land lines, nominally 600 ohm.

another way of getting rid of noise like that is using Differential signaling, commonly used in XLR plugs, where the regular signal is in one conductor and the 180 degree phase-shifted signal is sent over another, and in the other end the two signals are added and the noise is added too, and so it cancels out. ;) en.wikipedia.org/wiki/Balanced_audio look under 2.Interference Reduction and 3.Differential signaling this is however not common in most home or car audio equipment sadly

Car Audio systems are notorious for an alternator whine that changes frequency with engine rpm. This IS and probably ALWAYS WILL BE the fix for poorly isolated high-power car audio components. Isolators work every time. 😉

Clive, my mate had the same problem when he used his laptop+psu to drive a mixer for disco use, it hissed like mad and he came to me to fix it. I found a couple of line level transformers and plopped them into an old plastic film container, same wiring as your diagram, that was two years ago and all is still well :-D The magic of magnetic flux coupling :-)

It was common practice to put a filter (choke) in the alternator lead to reduce the whine in CB and HAM radio mobile installations.

For gigs I have a system consisting of a (musical) keyboard, plugged into a computer for sound generation, which is plugged into a mixer, which is then plugged into speakers. I have a problem with noise which I assume is two separate problems: 1) I hear very conspicuous humming on the signal, which I assume can be rectified with a module such as this, and 2) I hear what sounds like radio interference. I'm not sure how to solve the second problem, since I assume the case of the computer acts as a sort of shield (or does the composition of the shielding matter?). In any case, thanks for the interesting and informative video!

I apologize if somebody beat me to it, but in cars, the chassis is used as dc common, so the high frequency nose from so spark plugs can actually generate signals in the chassis ground loop between source and amp can transfer the audio noise through the chassis.

Fascinating!

I've created a computer room with audio from each computer to a central mixer. at each computer has two network connector one to the computer and the other to the audio from the computer , I use two transformers at each end of the network cable to the audio , they are not set as your 's but in series with the coils , I do not use the screen to something as I do not have some only the twisted pair network cable. The transformer is DA103C

Thank you ! .................... I think I need this from my PC Audio out to my Mackie Mixer . :)

Sorry if this has already been mentioned but balanced line signals are designed for longer distances. Yards and yards, sometimes hundreds of yards, with very puny signals, such as that which comes from a microphone. If you 'lift' the ground you have no signal ground reference but sometimes, as you mention, this can be preferable and the receiving device uses its own ground. The real magic is that the two signal wires carry the same signal but one is inverted. At the other end both signals are recombined and any external distortion, which could be rather inposing to such a little signal over a great distance, is conjured away by the inverted distortion cancelling out the distortion on the other one.... I think....

The alternator in a car, can make a lot of noise in the audio system :)

i emailed you the other day about this problem this should fix my issue. id imagine my issue is that the converter im using for high input has crappy shielding and is picking up the alternators noise.

Only mains hum (and AM radio broadcasts!!) I've picked up on audio gear is when I built a cheapo stereo amplifier kit, earthing did sort-of quieten it down, but, not enough to make it any good for anything other than the bin, everything else I've wired up properly and no mains hum... :P

ground loop isolator car audio can pick up alternator whine easliy so the metal case shields it to ground keeping unwanted sounds out. of the rca.

It's likely to reduce any EMI that the transformers might capture, and also the opposite (prevent that it leaks into other stuff).

I had to use exactly this to fix the hum in my car. This was back before portable digital music players were big, and I just wanted to use my laptop with an aftermarket head unit. The hum (in my case) was from the laptop, and not from the operation of the car.

Hi, I know this a late reply...but here goes... I bought a nice SoundDevices MixPre3 for my DSLR. This an awesome 3 ch mixer/recorder. The usual setup is to fit the mixer underneath the camera via tripod screw in the MixPre. *Both units operate on independent battery supplies.* The screw in the mixer is ground to chassis and the screw in the camera is similar too. A nasty ground loop happens when everything is set up and one takes the mixer output to camera mic in via 3.5mm jack to jack. You gets clicking, ticking sounds and others, which is probably the lens motors whirring away or the IBIS mechanism, all at around -40db....not good. Of course you still get a nice, clean recording on the mixer. I have been told that using something like this will make all the difference. What's you're take on that? I found a jack to jack + iso transformer by Monacor. Maybe double the price of others, but it looks the biz!

Nice topic, always faced the noisy connection from headphone output to input audio connections, until I've seen a japanese guy repairing old boomboxes and sometimes adding bluetooth function to them and using the ground loops devices. very interesting indeed! if soneone is interested hashy teddy is the name. nice old bomboxes being repaired in a professional manner.

The "screen" on his side is the "shield" of the cable on this side. Of the pond. Meaning the ocean. The Atlantic ocean. That big gob of moisture between here and there.

I use a Toslink optical cable to connect most of my equipment to my old Yamaha V800 6.1 receiver. As it needs optical light input to send audio, noice is not a problem. Most devices I want to connect have toslink-support but off course not every device supports toslink. In these cases, such a device is quite useful.

is the foil coupling the magnetic flux in the two transformer laminations

Been dealing with ground loops from varying sources and when it is gone it baffles me so upgraded to balanced and have an 8 channel di isolation but it is still there sometimes. Super annoying. Probably also from my old wiring in my house

I have the same problem in my car. I installed a switchmode power supply and some usb ports to charge my phone. However it makes a terrible mosquito like noise. I'm going to try to add filtering, but might need to get one of these.

Perhaps foil is for RF shielding or EMC type stuff?

I'm pretty sure that outer metal can provides zero shielding, since it's not grounded. If it is connected to one of the conductors in the cable, then it will act as an antenna, injecting all interference directly into your audio signal.

Great video. As a DJ of several years when I switched from using cd decks to a laptop I found I was getting a lot of background noise over my system from the laptop. Bought one of these from a nearby electrical retailer for £7 and voila! Problem solved.

It's like a miniature Faraday cage I am guessing to screen the possible inductance from the HV AC side of the alternator, I think the foil is a backup in case the cage separates..... Interesting though!

the noise problems in car audio dwarf those in the home and pro audio. most vehicles use the chassis as the ground, and then you have an amp grounded in the back near where the fuel pump and turn signals ground, a head unit that is grounded to some ground distribution bus, along with the AC fan and wiper motors. In most cases thr head unit also has a ground via the antenna coax - to a piece of metal that picks up noises from ignition systems, alternator pulses, fuel injector pulses... The best way I have found to deal with it is to run a twisted pair (ground & 12v) of 6 to 10 gauge wires from the battery all the way back to the amp. connect the ground to wherever the battery negative is tied to the chassis. put a fuse in and connect the hot side to the battery as directly as you can. Tap of these lines for the constant lead to the head unit. use at least a 10g wire between the back of the radio and solder it into the ground wire. this wire is so thick it shorts out the noise from the antenna coax. do not add any other ground points. let the amp be grounded under the hood next to the battery. now because we twisted the power and ground wires, we can run RCAs right next to them without troubles. do it some other way and it might work - for a while. do it my way and it stays working for the long haul.