Top Tips and In-Depth Review on the Garrett Ace 400

If I had to choose between any of the Ace series metal detectors from Garrett I would absolutely go with the 400 model. I am still very glad I started on my Ace 250 when I first got into metal detecting but now that I know what I know, the Ace 400 is much easier to use as a beginner/intermediate level metal detectorist. This in-depth review is focused on identifying exactly what makes the Ace 400 such a great unit as well as what tips can be used with this to make it an awesome unit to go dirt fishing with.


To begin with, the Garrett Ace 400 metal detector has a solid 4.4 start out of 5 rating according to over 200 reviews. So there is no doubt that this machine is loved by the users who have one. It can do pretty much everything necessary besides a couple of very niche things such as gold prospecting, underwater detecting, and saltwater detecting. Outside of that this machine will do it all.

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One of my favorite things about this unit is that it comes with a DD coil for it. All the other Ace series metal detectors come with varying sizes of concentric coils. Don’t get me wrong, concentric coils work great for their intended use, but, there is an undeniable advantage in 95+% situations to use a DD coil. That’s why DD coils are always considered upgrades. This is why I upgraded even my Ace 250 to a 5”x8” DD coil.

When looking at what differences there are between the Ace 300 and the Ace 400, the coil is the biggest difference besides the price. The Ace 400 comes with an 8.5” x 11” DD coil. The larger the coil is the deeper it will detect. The 8.5” x 11” coil is a medium to large sized coil but because of it’s DD shape it is still very lightweight. The DD coils are often about one half the weight as their concentric cousins. Because it is still a larger coil it makes it easy to have a search depth of 8” to 10” in the dirt.


I personally am not a huge fan of “air testing” depth on a metal detector simply because I have never actually seen those numbers correlate to real-world usage. I see it all the time where a metal detector will sense a quarter at 14” but when out looking at playgrounds and in parks it won’t find a quarter deeper than 10”. What the air test is good for is comparing apples to apples between machines to see which one will reach farther. The depth of the items tested in the air should not be expected when out in the field.

The Ace 400 consistently picks up coin-sized objects in dirt about 8” to 10” without much problem. The smaller coins often won’t be heard around the 10” mark but can still be heard at about 8”.

Frequency Type & Discrimination

It is a VLF (very low frequency) machine so it does very well in non-mineralized soils such as parks, fields, yards, and dry sand. Going into wet sand at the beach is a “no-go” for the Ace 400. It is not set up to handle heavy mineralization like the AT series from Garrett. It does a great job of finding coins, relics, jewelry and other metal items of value in freshwater beaches though, just not saltwater beaches.

The Garrett Ace 400 has very few cons to it and tons of pros. One of the cons though is that it is not Bluetooth/wireless capable. Where this isn’t a huge deal breaker by any means it is too bad it couldn’t handle Bluetooth since the unit is roughly $350 depending on the kit. It would’ve been a great feature to add to the 400 to help set it apart from the other Ace units.

It is definitely a beginner to an intermediate metal detector. As I mentioned before I started on an Ace 250 and I am glad that I did because I learned so much about metal detecting. Too often people think they can buy their way into knowledge and that’s simply not true. There is nothing that will replace good old-fashioned experience. It’s true that smarter technology can help curve the experience bar though. The biggest thing I wish my Ace 250 had that the Ace 400 has is the Iron Audio option. This is definitely an X-Factor that is very helpful. It is not too uncommon to find a target in the ground and it’s repeating very loudly and easily and is a nice high tone. This of course usually means aluminum or even silver. Digging high tones is obviously a must.

Iron Audio

It’s always sad though when digging a high tone to find out if it’s a bottle cap or something that should’ve been a low tone. This is where the “Iron Audio” option comes into play. First, the detector must have at least 1 notch in the iron section of the Target ID Bar discriminated out. I generally find that the bottom 3 notches are what I eliminate out. This gives me better chances of finding better targets without getting distracted by the low iron tones. But like I mentioned sometimes targets sound like high tones but should’ve had some iron tones too. The Iron Audio gives a grunting noise that you can hear before and after the high tone. This indicates that it is not actually a high tone type target but is in fact partially iron. This saves countless hours in digging up targets.

Even though the Iron Audio is very helpful it is still my opinion to dig everything that has a repeatable sound. But for those who are looking for higher chances of finding good targets in the shortest amount of time, the Iron Audio is a huge bonus. Since I hunt the majority of the time with the bottom three notches discriminated out the Iron Audio helps save a lot of time to not dig targets that are most likely no good.

This is why the Ace 400 is a beginner to an intermediate level metal detector. Without having some practice before on another machine, one might not understand exactly how to use the Iron Audio or why it’s so advantageous. If you haven’t purchased a metal detector yet and are looking into the Ace series, the Ace 400 is a great way to go but need to understand the extra features.

Discrimination & Target ID

It uses “Notch Discrimination” which is very easy to use and setup. Obviously, it’s not fun digging up a ton of trash targets all day long. We want the good stuff, even if it’s just modern coin, that’s better than nails and bolts. The different discrimination options make it easy to block out unwanted ranges of metal. I will often use jewelry mode because it automatically blocks out the bottom two notches of the target id range which is all iron. I personally prefer to have the bottom 3 notches discriminated out as I have found this reduces the amount of trash I dig. This gives me more time for better targets.

The Ace 400 has a 0-99 Target ID range which makes it easy to figure out what’s under the coil before digging it up. This is something that comes with experience that cannot be purchased. You’ll get used to what numbers are what kinds of objects. But again, this only will happen if you dig up every repeatable target until you get used to what numbers correlate to what objects. The Target ID numbers will tell you what the target could be and you’ll see at what depth it is at.

But often when at parks pull tabs or pop tabs will often be dug up because it’s a higher toned target. If I wanted to stop digging those up then I can do a couple of things to discriminate them out. Once I have found one, which is never hard to do, I can swing the coil over it numerous times to identify it. Then while the number is displayed click the “Discrim” button to then block out that notch. Now when I find that object again I won’t hear it so I’ll ignore it.

The other way is to simply see which notch is being highlighted when I swing over the target then click over to it using the plus and minus buttons then click the “Discrim” button to block it.

I personally never do this on anything higher than a 25, let me explain why. If I discriminate out a target that is ringing up 64 or 65 every time then I also discriminate out anything in the 57.75 to 66 range. So if there are good targets that ring up at 59 then I will be missing those too. See the chart here that explains the Target ID number ranges in correlation to the Target ID Notch.

Since the Target ID range is from 0 to 99 and there are 12 notches, that means that each notch represents a range of 8.25 in target ID. 99 ÷ 12 = 8.25/notch. As you can see in the chart there is an entire range that is being blocked out when discriminating. The Garrett Ace 400 cannot discriminate out a Target ID number. Where this is sad that it can’t, it’s not a huge deal. With all the Ace series detectors I have used and tested I generally will still just discriminate out the bottom 3 notches or up to a target ID of 25.

There are also presets that can be used for discrimination depending on what you’re hunting for. There is Non-Discriminate which will ring out on every single target ID, Jewelry, Coin, Relic, and Custom. Jewelry is my go-to if I’m not using Custom with the bottom 3 notches out.


As with most metal detectors the coil is submersible to a depth of about 3 ft. Basically, the control box cannot go into the water otherwise it will fry it quite quickly. I personally never go more than knee deep if I am using the Ace 400 or any Ace metal detector for that matter. I generally don’t go more than ankle deep in most cases because I like to set down my metal detector when digging. If I’m in any water at all I don’t want to risk the control box getting wet. If I’m doing any water hunting, I will bring a sling with me and attach it to the unit. That does a great job of keeping it out of the water.

It will go in freshwater but not saltwater. The saltwater is too mineralized and so the control box will just beep and readout like crazy and will not be any usable info. There is no ground balance option so highly mineralized soils will also not work well with the Ace 400. In my experience, if the dirt isn’t red then I don’t have to worry too much about mineralization. Sometimes it happens but very rarely. It also does not come with a threshold adjustment which is standard if there no ground balance option.


There are 8 sensitivity levels. In my experience, I have found that most of the time that each level of sensitivity is equal to about 1 inch of depth, roughly. It’s not an exact measurement. If I’m at a level 1 sensitivity I will still hear things 2 inches deep. When I’m at a level 8 sensitivity I will still hear things that end up being 10 inches deep. But I usually use that guide of 1 inch per level to help me when I’m out hunting.

The other way I use the sensitivity level is if I’m near any kind of power line. If I’m near a power line or any other underground/overhead cable, then I turn my sensitivity down which will often get rid of the interference. If there is still interference, then I will try switching to one of the four other frequencies that are preset into the Ace 400. I will also do a quick factory reset by holding the power button down for about 5 seconds or more until it beeps. Sometimes doing this will get rid of the interference from power lines too.


The 400 has a fixed 10kHz frequency that comes off the coil but also has some small adjustments that can be made which technically makes it a multi-frequency machine but not really. The default frequency is 10kHz and is F3 in the options. F1 to F4 are the options that come programmed in the control box. After talking with an official at Garrett, they explained that each setting is a slightly different frequency. So, for example, F3 is 10kHz and F4 is 10.2kHz. So there’s not truly a huge difference at all. This is why it’s not really a multi-frequency machine. Generally, multi-frequency machines like the Minelab Equinox 800 has 5kHz, 10kHz, 15kHz, 20kHz and 40kHz. The Ace 400 just has some minor adjustments that are made so that when detecting around others who are using the same Garrett Ace 400, you can switch to a different frequency and not pick up the other detectorists.

This is great if you’re ever doing competitions or events where other people have the same model or are at least on the same frequency. This I will also sometimes use if I am near a power line because sometimes just changing the frequency a tiny bit will help get less interference. But it is made to make it easier to detect around other people and not pick up their machines. If none of that works then I simply keep moving away from the power line until the interference stops.

Metal Tones

It is easy to hear if there is interference going on because generally, the control box will start reading out all across the target ID bar as well as all 3 tone levels will be sounding off. There is a low, medium and high tone which are very distinguishable. The low tone sounds like a 70’s era toy robot with a “meep, meep” sound that is very low and short. The high tone is also called a “bell” tone because it not only has a high pitch to it but also lasts a little longer and is like a ringing tone. The medium tone is essentially a slightly lower tone than the high tone and is not long lasting but much shorter. Having all three tones makes it easier to “hunt by ear” which is why I generally do so I don’t get motion sick staring at my LCD screen on the control box for hours at a time.

Once I hear a good high tone or mid tone on my machine, since I have low tones discriminated out, I then look down at the screen and check the depth indicator. The gauge that is on the Garrett Ace 400 is a 2” to 8+” gauge. Some things to note though are that very small objects can be shallower than indicated and that very large objects will be deeper than indicated. The depth gauge is based on average coin sizes. And since this is the US version it’s based off of US coin sizes.

I have dug up flattened soda cans 10” deep that read out 6” deep. Also, it is important to know that when pinpointing, if the target ID bar goes from 0 to 99 very quickly then the target is probably shallower than 2 inches of depth. If the Target ID bar gradually goes from 0 to 99 rather than jumping, then it is most likely the depth that is indicating on the depth gauge.


One of my favorite things of the Ace 400 is how to pinpoint with it. Because it comes with a DD coil there are multiple ways to pinpoint an object. The obvious is to place the coil to the side of the target about 12 inches away. Then hold down the pinpoint button and slowly scan left and right, then forward and back until the middle of the “X” has been found.

Another way is to place the coil to the side of the target about 12 inches away then hold the pinpoint button. Rather than trying to visually map out where the target is by moving it back and forth and guessing the center, there is an easier way. Holding in the pinpoint button you go left and right then forward and back but right when the tone cuts down on the tip of the coil, that’s where the target is. The same can be done off the back of the coil. Move the coil forward over the target until the one cuts down, right at the back of the coil is where the target is.

The third way is a little faster in my opinion and takes a little practice. It’s called the “DD Wiggle.” This only works with DD coils which is why I love the fact that the Ace 400 comes with a DD coil. Without ever having to push the pinpoint button the target can be pinpointed. Once you can swing the coil over the target and it continuously rings up, simply wiggle the coil left and right an inch or so at a time and slowly bring the coil back. Once the ringing stops, the target is at the tip of the coil. The same can be done off the back of the coil by wiggling it and pushing the coil forward. Once the ringing stops, the target is right where the back of the coil is.

Doing the wiggle method has helped me get targets out of the ground faster since I don’t take as much time pinpointing exactly where it is using the pinpoint button. All the methods work fine, and the wiggle method is only faster once it has been practiced enough times. It is important to keep an eye on the tip of the coil that you’re moving the target towards but also the depth gauge. It is not fun to dig 6 inches down when the target is only 2 inches down and vice versa.

Shovels & Depth

I prefer to use either a small hand shovel or a mini root slayer shovel. If the target is 2 inches or less, then I use my hand shovel. If it is any deeper, I will usually use my mini root slayer shovel. I try not to dig deeper than the indicated depth. I try my best to dig as deep as the target is and then when I pop the plug out it is usually right on the bottom of the plug. That is the fastest way I have found to dig out targets.


It’s nice that the Ace 400 uses 4 AA batteries because they are easy and cheap to keep on hand. I always keep an extra set of 4 batteries in my detecting belt just in case my battery dies while I’m out hunting. I have found that the Ace 400 lasts about 70 to 100 hours of continuous use depending on if headphones are used and how much I use the pinpointer. It will usually last me a couple of months before I need to swap them out. That’s when I’m just using the Ace 400, I detect with many units, so I rarely have to change their batteries. I generally go with 1.7v lithium AA batteries because they won’t go bad on me if they sit in the machine a long time. I’d be wary of leaving normal lead acid AA batteries in for extended periods of time because they can corrode.

I usually take my truck to go metal detecting and so the detector is in the cab with me which is a nice ambient temperature depending on the time of year. But I will often take my kids to the park and metal detect while they play, and my wife will come and read a book. Since we take her SUV when we do that the detector is usually in the back and not in the air conditioning. During the summer I do notice that sometimes I’ll pull the detector out of the trunk and the screen has some rainbow colors on it. I’d be mindful of leaving it in hot places or even extra cold places too because electronics do best when they’re room temp or slightly cool but not hot or cold.

Either way, the Garrett Ace 400 has a battery level indicator which is very accurate. I always swap my batteries once I hit 1 bar, I’ve never actually run mine until dead.


Like all the Garrett products the Ace 400 comes with a 2-year manufacturer warranty. So, if for any reason the detector is having issues like interference when there is nothing to interfere with it, then they will take care of it for free. I have spoken with their customer service multiple times and they are very helpful.

Pros & Cons

The biggest things I like about it is that it has the Iron Audio grunt noise option, multiple frequencies, comes with a medium/large DD coil and is very lightweight. The biggest let downs are that it doesn’t have Bluetooth capability, and isn’t more water resistant. It’ll handle being in the rain just fine but not submerged.

Pricing & Kits

The best Kit I have seen is about $365 and comes with everything needed like a control box weather cover, coil protector, headphones, batteries, carry case and user manuals. There are other kits that range in price from $386 to $536 that also include a pinpointer, hand shovel, and other things. I personally just did the $365 kit because I already had a handheld pinpointer, shovel, and other accessories.

I will have other articles about the different handheld pinpointers I have tested, different shovels, headphones and so on.


I personally think that a coil cover and control box environmental cover are must-have items in the kit. I never use the carry case because it takes up more room than just putting in my detector. I personally hate the pouches that metal detector companies like Garrett offer. It’s more of a personal thing than anything else because you definitely want to have a pouch of some sort while out dirt fishing. I use a personalized MOLLE belt that is amazing, comfortable and helps me keep things organized.

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My favorite shovel has been the Root Slayer Mini Shovel for sure. I use that in conjunction with a tool holder called the “Gunnie.” It keeps the shovel out of my way while detecting, and I can even crouch down and it doesn’t hit the ground or anything.

Final Thoughts

I upgraded from the Ace 250 to the Ace 400 once I had hundreds of hours of practice with my Ace 250. I find that the Iron Audio is very helpful and the bigger DD coil helps me find good treasures in very trashy areas. If you’re looking into upgrading then you may want to take a serious look at the Garrett Ace 400. If you are new to the sport then I’d HIGHLY recommend it I am very grateful for all that I learned on my Ace 250 but I believe a lot of pain, sweat, and effort would’ve been saved by using the 400 instead. It’s definitely worth every penny.

Instructional Videos

With all the other Ace metal detectors such as the 200, 250, 300, and 350, they all have 1 instructional video. The Ace 400 though has 3 instructional videos. These act like the user manual in a way but showing how everything is done. Here are those 3 videos:
Instructional Video 1

Instructional Video 2

Instructional Video 3