Upgrading A Squier J Mascis Signature Jazzmaster

There have been many articles about upgrading Squier guitars and modding them with better parts. One of the more popular models being the J Mascis Signature Squier Jazzmaster. In my opinion it’s a fantastic guitar at a fraction of the cost of any American or Mexican made Jazzmasters. Out of the box the guitar is definitely good, it’s not great but for the money you’re spending you are getting some serious bang for your buck, and with a little bit of research and some basic knowledge on the inner workings of a guitar you can make yours a tone monster with a cost effective budget.

I know what some might be thinking, ”Why invest all of this money into a guitar that is less than $400?” I wouldn’t think about it that way. If you like tinkering with guitars and want to learn more about their inner workings and experience it all first hand then it’s a great place to start. If you have no aspirations with doing that then move onto getting a vintage reissue or something in that ballpark that better suites your style. For me I had always wanted a Jazzmaster and was curious with what every switch does and how each component can affect the overall sound. I learned a lot from upgrading my JM and in the end I came out with a great sounding guitar that I won’t be bummed taking out on the road and thrashing it around. After all, its just metal and wood!

So let’s dig into the process of what went into upgrading my guitar…


Find A Good Used Deal

First things firsts you need to buy the guitar. You could go the route of buying it brand new but since your going to be gutting most of this thing anyways why not get a good used deal, ya know? You can go on Reverb or search your local craigslist and find these guitars for less than $350 easily. The reason I chose the J Mascis model is for obvious reasons. Im a big Dinosaur Jr fan and the white with gold anodized pick guard is a classic look. Also, it already came installed with a tunomatic bridge as that is J’s preference and the neck surprisingly felt great. You can choose whatever model you would like but this article is based solely around this model.

Upgrade The Wiring Harness

Start here before changing out your pickups. In my opinion you will really notice a huge difference by upgrading all of the wiring in the guitar. Yes, this is a cheap guitar and includes some cheap components. I upgraded the wiring to Gravity vintage cloth, and the pots to 1 MEG CTS, and 1 Fender 1 MEG Solid Shaft Linear Roller Pot for the volume and 1 Fender 50k Linear Solid Shaft Roller Pot for the rhythm circuit. As you can tell I was going for a vintage jazz master sound and went with what you would typical find in something from that era or in a vintage reissue model. Now you can either buy all of these separately, save a bit of money and hook it up yourself or buy a prewired kit such as this one. The choice is yours. But do this with the original pickups and see if you notice a difference, you might find yourself liking the stock pickups and save a bit of cash.


The Pickups

Believe it or not the ones that come stock in this model are in fact p90’s and they sound pretty good. So, upgrading all of the components will only make them sound better. If at the end of the day you’re not happy with how they sound then swap them out for something new. I went with Seymour Duncan Antiquities because that is what I am used to, plus I wanted something as close to the vintage Jazzmaster sound as I could get. You can obviously go any route with pickups. Curtis Novak are very popular and you can get any type of pickup housed in a JM pickup. So if you wanted a humbucker, but still the look of the Jazzmaster pickup you can do that! I recommend upgrading the pickups. I would also recommend checking out Lollar pickups if you haven’t already.

The Bridge

Right, so as most people know a lot of techs and players recommend upgrading the bridge on these guitars due to the inconsistency of the original bridges. Unless you like having your strings pop out of the saddles every time you pluck. However this guitar comes stock with a AOM/TOM bridge as that is what J did for years on all of his Jazzmasters. These work but not all that well if you ask around. Adjust-O-Matic / Tune-O-Matic bridges are not the correct radius for Fender guitars (7.25″ and 9.5″) and the problem can not always be corrected properly. Plus these bridges don’t tend to solve the original problem of buzzing and stability staying in the saddle slot. A shallow saddle slot means the low E string can still pop out, just like the Vintage saddles.

I would recommend swapping out the bridge out for a Mastery. Everyone does it and there is a reason, and it’s because THEY WORK! Removing the AOM/TOM inserts, filling the holes. and re drilling is required but I did neither of that. Upon recommendation from Mike & Mike’s Guitar Bar (who also wrote a great article about this very topic) I would recommended using Staytrem inserts that simply pop in place of the AOM/TOM thimbles and allowing the mastery to drop right into place with ease. It’s very simple and requires no filling and drilling! I would say without a doubt that the Mastery bridge and Vibrato replacement were the two most important mods that I did on this guitar to get it to perform the way it was suppose to!


The Vibrato

My guess is that if you are playing a Jazzmaster or wanting to explore one for the first time that you want to use the vibrato. After all that is one of the many great features with these guitars. However the Vibrato that comes stock on this guitar is cheap and not very efficient. It also makes a squeaking sound every time you move the trem arm and it gets really annoying real fast. So as recommended by other fellow JM lovers I upgraded the Trem to an American Vintage Reissue by Fender. They’re used on the AVRI Fenders and I believe the new American Professional line of guitars as well. The Trem I purchased came with a longer arm with a nice gentle bend that makes it very comfortable to play.

I vividly remember feeling how different this tremolo felt as soon as I screwed it onto the body and strung it up to play. The tractions is smooth and easier to use. It actually feels like how you would want a vibrato to feel. The inner workings on these tremolos are very important and when made poorly it can really affect  the tuning, stability, and even the tone of the guitar. Plus, the term arm stays put and doesn’t fall out! That right there is a huge help.

I also set up the Trem-Lock feature after figuring out what it really does and how it works,  my mind was blown. Basically the Trem-Lock is that medallion looking thing at the top of the Trem. When setup properly it will allow the tensions of the strings to remain intact if for some reason you break a string, allowing the rest of the strings to stay in tune! How cool is that? Setting it up properly is key though and that is a topic for another discussion down the road.


Alright now to wrap all of this up, obviously it can get pretty costly upgrading such a cheap guitar. I get that. However for me this was my first Jazzmaster and I wanted to explore how everything works and how to improve it. So I couldn’t think of a better project than to put in the work on a great inexpensive guitar. Like a stated before, I am a big J Mascis/Dinosaur Jr fan but didn’t think I could pull off the purple sparkle finish (his original Fender Signature Model). To me this seemed like the perfect place to start. I would say the most important things to upgrade would be the bridge, vibrato, a few of the electronics (pots, capacitors, etc…) and you got yourself a pretty rad guitar. I decided to take it the extra mile and go with a new wiring harness and mint green pick guard to differentiate it from the Gold Anodized guard which I don’t mind at all to be honest. It’s also a lot of weight off of my shoulders having this guitar out on the road knowing that it doesn’t cost as much as my Gibson and Fenders. If anything happened to this while flying or touring I wouldn’t be that concerned as I could probably fix whatever happens to it. And may the gear gods forbid it ever getting stolen, I can always find another one and do the exact same modifications to it, or more!

Its an overall great guitar now and fun to pickup when I need that JM sound. These are also some of the most comfortable guitars you can ever put your hands on. They just mold right to your body when your playing, and they look pretty darn cool as well. I can’t recommend them enough. I would love to see what others have done as well, so if you have one please share!

10 thoughts on “Upgrading A Squier J Mascis Signature Jazzmaster

  1. Do you have a link or resource for the Staytrem inserts you talk about here (for the Mastery Bridge no-fill/no-drill solution). I’m still digging through various forum threads in the meantime. Thanks!


  2. Great Article, and amazing looking Jazzmaster. I will reference this and Mike’s in the future, rebuilding one. I know that neck is wonderful so I’ve been eyeing J’s JM for a while, haha. Thanks


  3. I’d love to put in a Mastery bridge but I have no woodworking skills and don’t want to pay a luthier to re-drill the holes. I contacted StayTrem about buying just their thimbles (like you did) but they said they didn’t sell them individually and that they wouldn’t work with any other bridge.

    Do you know of any other method that would work? Should I just bite the bullet, buy the M1 kit and pay a guitar tech?

    Thanks for this run-down! My JMJM is my favorite guitar I’ve ever owned, just as it is, and I’m excited to make some upgrades!


  4. I own a 2011 j mascis jazzmaster and is absolutely wonderful, I don’t agree with many of comments in this article. The tremolo arm works amazing and doesn’t make any noise. Also the bridge has the right radius and stays in tune all the time and I play a lot of surf rock, so I’m beating that sucker all the time. The most incredible thing about this guitar is the neck and the jumbo frets, this neck is even better than the stock one in American made guitars.


  5. staytrem doesn’t seem to have the bridge inserts nor seem to ship outside UK anymore, is the only option now to fill and re-drill the bridge holes for a mastery?


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