Setup and Maintenance
 
Because the banjo is largely a bolted together assemblage of wood and metal, there is a great deal of setup and maintenance involved in getting it to top form and keeping it there. Wood expands with moisture. Metal expands with heat. The two counterveiling factors combine to make for an almost day to day variation in tone. Simply transporting the banjo across town can cause enough jiggling to loosen things. Here's a list of key elements to be aware of that will from time to time affect the tone and require tweaking:


Fit of neck to pot:
The banjo is one of the most poorly balanced instruments, as anyone with a bad back can tell you. Most of the weight is contained in the pot assembly, leaving this relatively fragile stick of wood jutting out the side, bolted through the rim with a couple of lag bolts. Some banjos will go out of tune simply by playing them while standing up, supporting the weight from a strap instead of laid in your lap. Even the tightest neck fit will distort the tone when stress is put on the neck, and in fact, Scruggs and other players actually bend the neck from time to time to create vibrato, or to drop the pitch.
The neck fit to the pot is very complex. If you look at the profile of the pot (rim, ring, flange, hoop) you will see that there are several different radii.
 


Cutaway profile of the banjo neck to body fit


Add to this the slight angle of the neck to the body, and you have a fit that is, at best, about 70% contact. And yet this fit is critical to the sound. Because the neck becomes a part of the mass of the instrument, it's vibrational qualities affect the resonant frequency of the whole structure. A loose fit can kill the tone, and cause intonation problems.
What to look for: Check that the rods are snug to the neck side of the rim, then check that the nuts that lock the rods in place are tight.
 

Cutaway view of the banjo showing the structural components


I would definitely advise employing the skills of an experienced luthier if you seek to change the angle of the neck to the pot. Let's say, for example, you upgraded your tone ring and rim, and the pot profile is now different. Some of this can be made up for with shims (I have strips of hardwood veneer that I use for this purpose), but too much shimming can lead to a "soft" fit, and the real issue of neck heel cut should be addressed.


2) Adjusting String Height - Action: If you look at the illustration above, you can see that not only do the coordinator rods serve to lock the neck to the rim, but that by manipulating the nuts on the lower end of the rods (away from the neck) you can push and pull in tiny amounts by running the nuts in or out on the rods. This serves to distort the rim just slightly which will in turn push the neck angle up or down. This is used to change the height of the strings over the fingerboard, what is referred to as the "action" of the neck. CAUTION: Only tiny amounts of adjustment are appropriate for this method. If you need to change the string height more than a 1/16th of an inch, change the bridge to one of a different height. Distorting the rim is potentially destructive to the wood rim, but is in miniscule amounts a safe and effective way to fine tune the string height.


3) Neck Relief: This is an often misunderstood concept of acoustic instrument neck adjustment/design, not to be confused with "action" or string height over the fingerboard as mentioned above. Neck relief is, simply put, the amount of bow that exists in the neck. Folks often assume that the fingerboard is - or ought to be - complete flat. In fact, a slight upward bow at both ends is necessary to keep the strings from buzzing against adjacent frets. This adjustment is made by manipulating the nut on the peghead end of the truss rod which is typically found under the truss rod cover just above the nut. Your banjo may or may not have come with a little tool that has a quarter inch socket on one end for adjusting the nut.

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To increase the "flatness" or remove bowing, run the nut in, clockwise, to tension the rod, forcing the neck flatter.

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To add bowing to the neck, decrease the tension by turning the nut counterclockwise. Note that changes to the truss rod


4) Bridge Height/Selection: There are literally hundreds of banjo bridges available. Most come in a fairly short range of heights, though, ranging generally from 1/2 inch to around 13/16ths. As I mentioned elsewhere on this site, in my view, next to the tone ring, nothing on the banjo effects tone more significantly. If you need to lower or raise the string height more than 1/15th of an inch, it's time to look at a different height bridge. When setting up a banjo, my own personal preference is to set the neck so that the string height will be playable with at least an 11/16ths bridge. I think my archtop currently has a 13/16th on it. The increased string height over the head gives the added bonus of causing fewer pick strikes on the head. However, Earl has played half inch bridges forever, and he doesn't seem to have much trouble.


5) Head Tension: There's a lot of really soft science involved in setting the head tension on a banjo. Just remember that most of the classic early recordings of Earl Scruggs (eg: "The Mercury Recordings: Flatt and Scruggs") were done on a banjo with a skin head pulled as tight as he could get it. Methods abound, from using "head tension gauges" to tapping the head and "tuning" it to a particular pitch. My general rule of thumb is that the head should be very tight, but not so tight that the sound begins to "thin out" and loose bass response. I have no method for measuring this other than my ear. Also, I have found that head tensioning issues usually serve to mask a larger problem, like a poor tone ring, or bad setup. When tensioning bracket hooks, try not to load all the tension up on side at a time by going in a circle. Instead, torque one hook nut partially, then torque it's counterpart across the banjo. Next, move over one hook, then it's counterpart. It's a little harder to keep track of, but it prevents from loading up one side potentially causing a rim or flange failure. I've seen many of them. Flanges, even the best of them, are made of what is essentially pot metal and will bend and break fairly easily. Warped flanges from poor head tightening practices are fairly common.


The standard banjo head these days is made of Mylar, (although skin heads are still available and used by some), a very strong plastic that has almost no stretch value. It can pop, though, when it is overtightened. Because of this, you can tighten the head for quite a while before effecting the tone at all, until the head reaches it's stretch range. Then, just a half turn of a banjo bracket can make a large difference in tension. Never turn the bracket hook nuts until they squeak. You are in danger of head or flange failure at that point.


6) Tuner Maintenance: If you are having trouble keeping your banjo in tune, check the tightness of the button screws. These serve to both hold the buttons on, keep the tuners together, but also to increase friction. The tuners should turn freely to the touch, but not if bumped, and certainly not by string tension.


7) Nut Lubrication: Graphite powder from a pencil serves as a great lubricant in the string slots. Get some fine sandpaper and rub a pencil "lead" on it to form some powder. Sprinkle just a touch in each slot. This takes a little practice and is rather messy, but well worth the effort.


8) Tailpiece Height/Angle: There's not a lot of agreement here on just what sort of impact on tone is generated by changing the height of the tailpiece, but my thinking is that the lower the tailpiece, the smaller the angle created by the bridge and strings (see below), which ought to create more downward pressure of the bridge on the head for a given string pitch. Does this transmit as increased volume (amplitude)? Perhaps. Some say that a higher tailpiece will create a softer, mellower tone. I've always run mine low, and some folks always run theirs high. My advice is to simply try it yourself. See if your ear can detect a difference in tone. If so, go with what pleases your ear.
 


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