Jazzmaster Buzz Kill (and Crackling and Humming)

Picked up my very new 2020 American Professional II series Jazzmaster last night intending to do some recording and got totally sidetracked by an unusual humming/crackling noise being created by the tremolo arm. Here’s an explanation of what the issue is and how to fix it. Spoiler alert: it’s very easy.

Reproducing the issue

What I was hearing was a very loud humming and sometimes a crackling or buzzing sound. Now, Jazzmasters are loud to begin with and hum is just part of the Jazzmaster experience but I knew this was excessive. At first I thought it was an issue with my patch cables and pedals. So I checked every single patch cable, took the power supplies out of the equation, plugged directly into two different amps and used two different cables to see if it made a difference. It did not. Whenever I touched the tremolo arm the humming got louder and when I moved the trem arm the humming would turn into crackling and buzzing and was so loud that it was overpowering the sound of the guitar itself which made me absolutely sure that this wasn’t just a Jazzmaster being noisy. I even turned off all my lights, unplugged a bunch of appliances, and made damn sure that there wasn’t some sort of electromagnetic interference that somehow turned the tremolo arm into an antenna. Still the issue persisted and it even happened when I only moved the tremolo arm by the plastic end and not touching the metal at all.

The source of the problem

The problem was a grounding issue. Most hum problems are grounding issues. Yes, single coils will pick up EM interference and can be loud, especially on Telecasters and even more so on Jazzmasters but unless you’re playing on the grounds of a power plant or something, there’s an acceptable level of hum you should be able to overcome simply by using some shielding, properly grounding the electronics of the guitar, simply moving around until you find a position where the hum is least pronounced, and using some plugins or hardware like a noise suppressor.

But if you have a grounding problem then the only way to fix it is to open up your guitar and do some simple work. I was hesitant to open my trem cavity because I just don’t like unscrewing the screws in the wood of the guitar for fear of loosening them over time. So before doing surgery on the guitar I took a short length of wire and connected it to a part of the guitar I knew (or strongly suspected) was grounded properly and connected it to the ungrounded piece; in this case it was the tremolo arm. I used a small piece of copper tape that you get get for shielding your pickup cavity and used it to tape one end of the wire from a patch cable to the nut of my output jack (which is the most reliably grounded place on your guitar) and used the same tape to connect it directly to the tremolo arm. I then touched the trem bar. No scratching or crackling sound. I swung the trem bar around a little and used it to create a little vibrato on a strummed chord. Very little to no noise. This was confirmation that I needed to ground the tremolo arm somehow but I wasn’t sure how.

You can use a multimeter to check whether two parts of your guitar are grounded or not but I’m not very familiar with my multimeter and setting the bias on my output tubes is the extent of my ability with it. But if you’re capable with a multimeter then use that instead of running wires from place to place. It’s just easier when you diagnose the problem that way.

Most guitars will be grounded by a wire running from the control cavity to the tremolo claw (like on a Strat) but Jazzmasters have a few common ways of grounding them and some people recommend drilling a hole in your control cavity into the trem cavity and running a wire through there to connect the grounding from the control cavity to some piece of metal under the tremolo plate. I would advise against that if you can as these guitars are made to be grounded in specific ways and if your guitar doesn’t already have these holes in it then there’s probably a different and easier way to fix the problem.

How to fix it

So what I’m about to describe will work in the American Professional II Jazzmasters for sure. It’s likely to work for others but I cannot confirm that.

When you get a new American Pro II Jazzmaster you’ll notice there’s a little piece of paper that tells you to take the tremolo plate off and adjust the tension screw that holds the tremolo arm in place. This is the screw that controls how easy it is to push in and remove the tremolo arm and how freely it will swing around when inserted. What that paper doesn’t mention is that there’s a ground wire coming through a small hole from where the input jack is into that trem cavity and there’s a wire in there that makes contact with the tremolo plate. That’s how these guitars are grounded.

I adjusted my tremolo arm tension first thing when I got the guitar and never had an issue with the tremolo arm crackling but I opened up the tremolo cavity by loosening all the strings, unscrewing the six screws you’ll see around the outside of the plate and and removing the tremolo unit. In that cavity I saw that ground wire that I never noticed before and I saw that it had been slightly frayed. It seemed as though it was making contact with the tremolo unit but loosely and must have been losing contact with the metal of the tremolo unit whenever I pushed and pulled on the arm.

I pulled the wire a but to get some more slack and placed the exposed bit of ground wire in such a way that it was bent. First I twisted the frayed bundle of wires so they held together better, then bent it so that the tip of it was directly covering the screw hole and the bend of the wire brushed up against the wall of the cavity. I used a very small square of the copper shielding tape to hold the wire flush against the wall of the cavity while the bend went over the top of the guitar and over the screw hole. This ensured that not only would the metal that butts up against the wall of the cavity make contact with the ground wire (that was now taped with conductive material so it wouldn’t move with friction) but the part of the ground wire bent over the top of the guitar would also be held down by the pressure of the trem plate being held down over it as well as touching one of the screws that is holding that plate down. So I basically ended up with at least three points of contact for the ground wire beneath the tremolo plate and because the plate covers a small area around the cavity, you never see the ground wire at all and it keeps the guitar looking beautiful.

How did this even happen?

I use the hell out of my tremolo arm on my Jazzmaster and my theory is that I probably shifted the wire (which was never held in place by anything but friction) a little when I adjusted the tremolo arm tension initially but not enough to cause this issue. Then, over the course of the three or four months I’ve had the guitar, the moving parts under the tremolo plate must have been brushing up against that wire and began to fray it and move it out of place the more I used the tremolo arm until it finally got to a point where it wasn’t making consistent contact with the metal parts of the tremolo arm.

This may happen again in the future and if it does I may decide to solder the ground wire to the trem plate but for now the copper tape I used to keep the wire in place should prevent friction and fraying or loosening of the of that wire later on.

So there you have it. I can’t tell you how hard it is to find a detailed solution to this issue. There are a lot of forum posts describing the issue very well and lots of people diagnose it correctly but I didn’t find a single in depth tutorial on how to go about fixing it. What’s worse is that because the American Pro II Jazzmaster is so new, there wasn’t a single answer tailored to that specific model. So if you have any Jazzmaster at all this will likely work for you and if you have the American Pro II model then I hope this helped you find the answer you were looking for.

I can now touch, wiggle, and jiggle my tremolo arm as hard or soft as I want and the only sound I hear is that sweet sweet subtle vibrato that you can’t get anywhere else but from a Jazzmaster.