Fender Jazz Bass with Uneven Action and Back Buzz

Got a Fender Jazz Bass in the other day....the action, (height of strings) got higher as it went up the neck, (toward the body). The truss rod was tightened all the way. The owner wanted the strings level all the way up the neck. What do you do? I heat the neck to reshape it so that the neck does not have what I call a "ski jump" at the end of the neck, (end is frets 21+).  Once it is level then I can use the truss rod again and have plenty of travel left in the rod after it is adjusted.

When there is a "ski jump" at the end it causes fret buzz when played between frets 12 through 15, when the strings, or action, is lowered. It is because the fingerboard is higher around fret 20 and lower around fret 12, or in other words fret 12 area is in a valley, and fret 20 is higher than 12.

The way to cure that is to tighten the truss rod, which raised the valley, or straightens out the neck. If the truss rod is already tightened all the way, then you can't get rid of the valley. There may be a compound problem, the truss rod may make the area between frets one and twelve too straight or give it a back bow and will not "raise the valley" in the area of frets twelve through twenty one. That is where the heating comes in.




Of course once the strings are closer to the neck and if there are any uneven frets they may cause a buzz, then would require fret leveling, and rounding out frets and polishing, (the rounding of the frets and polishing is assumed, always should be included in the leveling process). I can talk about fret work in a later post....

Back to the neck heating. The neck bender is an aluminum block the length of the neck the gets very warm. You place it above the fingerboard, not touching the frets, little shims hold it up off the frets. It is then clamped to shape the neck the way you would like it to be shaped. Simple. Not really, don't try this at home, I have had training and years of experience at it.  It still scares me every time I have to do one! Wood has a personality and a mind of it's own, never sure how it will react!

Heat and cool overnight and then string it up and see how it looks. If all goes according to plan it will have a nice gradual relief, or forward bow, and not have a "ski jump" at the end. It will have a nice level surface with clearance for the low fretted string to vibrate and not hit the frets, thus causing a buzz.

To make matters more complex, if a bass has a very straight neck and there is no fret buzz it may have what I call "back buzz".  That is when you press,  for example,  at the seventh fret, pluck the string and there is a buzz that comes from the length of the string between fret seven and the nut. You can not hear it through the amp, but you will hear it acoustically, or feel the vibration in your hand. The string is not high enough above the frets or it is not pressing firmly on the fret tops, and it is rattling.

To cure this problem you need to either loosen the truss rod to give more clearance or raise the nut. If you loosen the truss rod you will then get the "ski jump" back.  To complicate it even more, this particular bass had a "back buzz" when the fourth string was pressed at the seventh fret and the first string was pressed at the seventh fret and either both notes played or if just the first string was plucked. A nasty rattle occurred.  I raised the nut and looked for a high fret between frets one and seven. Found fret five to be a little high. Some necks shape differently under tension, humps or bumps may occur when it is strung up, thus looking different when unstrung to do the fret work!  After many things were tried the buzz was less. I then asked the customer if he wanted to continue to pay for more work or did he really need to play these two notes?  His reply was no that's ok I will use a different bass if I need to play those notes. Here's the funniest part, his other Jazz Bass did the exact same thing. They were both new, same series.

I have a way of not being able to say this instrument will not perform as you want it too. Then requiring higher action, some people want something it just will not do. Some will only play perfectly with the strings at a particular height and that will be the best it will do. I have to learn to stop trying to make it do something it probably will not do. I will go in on the weekends or on my own time, not charging the customer, but the end result is usually I will loose time and money on it.  Reminds me of what I tell customers, it is hard to shop on line, you don't know what you are getting. It may not do what you want. Do violin players shop on line? Maybe now they might but I always thought they would go to long lengths to try out the instrument and get the one that really suits them.

I am often setting up guitars from on-line shoppers who say can you make the action lower without the buzz? The answer is, not always, unless you want to pay for extensive work. You can always plane the fingerboard to reshape or remove bumps. That is expensive, the frets are removed and the wood is planed, then frets go back in. Usually cost more than what the average owner of a new instrument of lower value wants to pay.   It just seems as if it is the "nature of the beast".  Every piece of wood is different, every grain, every knot, all adds up to the final sum. This is what it is and it sometimes is hard to change.