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Perplexing setup: buzzing 8-16th frets w/loose truss rod

VifferMike

VifferMike

Registered Four Banger
Dec 10, 2004
449
36
Dallas, Texas
www.facebook.com
#1
I switched to a balanced set (45-60-80-107) of D'Addario XLs on my Modulus Genesis VJ, which necessitated a fresh setup last night. It wore XLs (likely 45-65-80-100) when I got the bass a couple of months ago, and it played like butter save for a little A/D string buzzing around the 4-8th frets when I really dug in.

I followed the Jerzy Drozd setup guide in terms of task order:
1. String change
2. Radius-match saddle height (without a template; used measurements at last fret since the Mod has a compound-radius neck)
3. Neck relief/truss rod
4. Saddle height/action
5. Intonation
6. Pickup height
With some assistance from Tony Nagy's setup guide in Premier Guitar -- which, I've noted, follows a different setup task order.

During the truss rod adjustment process, I loosened the rod counterclockwise at least a full turn to get the proper 8th-fret relief (@ .45mm for my style), which surprised me -- yet the result was gobs of buzzing everywhere above the 6th fret. I raised saddle heights to a point well above my normal preferred action (@ 2.0mm E/1.6mm G, at the 12th fret) -- I'd say as much as a full millimeter in places -- and I'm still getting pretty bad buzzing on the A and D string between the 7th and 15th frets -- with no buzzing high and low on the neck.

What's going on here? With a relatively high-tension string set and the graphite-impregnated neck, this is the last thing I expected to encounter ... I did note that using Nagy nut-height test (clearance at the first fret with the string depressed at the 2nd fret should be @ .3mm: the thickness of a business card), the A and D strings nearly fret out. Is the Mod's nut too low at those strings (didn't seem that way when I got the bass)? Frets are a tad worn, but not horribly, and the wear's even. Should I let the neck settle for a couple of days, then re-do the setup? Should I try a different setup task order, such as Nagy's?

(Also, I suspect that the truss rod is completely loosened since it turns counterclockwise completely without resistance and hits a 'bump' about a quarter turn more counterclockwise now. ***?)
 
#2
how is the nut height?

modulus makes nice stuff; as such, the fretwork quality should let you go with a straighter neck.

get the strings nice and low over the first fret, and try like .010" relief. that should get the strings closer all around, which should let you raise the saddles more while still having comfortable action, which should help with the buzz from the middle of the neck.

don't forget to "seat" the strings (especially the fat ones) by pressing on them at the witness points to eliminate any curving.
 
#3
Thanks for the feedback, Walter. :) I've done a number of setups before; I stretched the strings along their length and seated them at each witness point.

The nut height seems OK; all are uniformly a hair under 2mm from bottom of slot to top of fingerboard. What I'll do over the weekend is take that 1st-fret measurement (.010"/.254mm relief) under all four strings to see if it's uniform. I'll also use a metal straightedge to check for high frets, though I don't think that's the problem since the buzz doesn't start at a specific fret on either the A or D string.

The neck's compound radius may be what's causing this since I set initial string/saddle height at the last fret, and the radius difference at the first fret could be a niggle that I'll have to deal with.

Also, I've turned the truss rod so that it's slightly engaged now (by 1/8 turn) instead of at its loosest. I will say that letting the bass sit for a day has allowed the new strings/setup to settle, and the buzzing's less severe and in fewer places. But it's still there.
 
#4
VifferMike said:
The nut height seems OK; all are uniformly a hair under 2mm from bottom of slot to top of fingerboard.
Click to expand...
that's not a useful measurement; all that matters is the height of the strings over the first fret.

it should be only barely higher over the first than it is when you fret the first and look at the second fret.
 
#5
Walter,

So: .010"/.254mm between the top of the first fret and the bottom of each string (tuned to pitch, of course)? This measurement should be taken with open strings (i.e., nothing fretted or capo'd)?

Interesting. I'm assuming that this is one of the proper measurements to use for determining the depth of a nut slot, yes? (Always wondered that).
 
#6
no, the .010" figure is for relief, with the string held down at the first and last and measured at the 8th fret.

once that is set to be good and flat, look at the height over the first fret. .010" is decent, maybe a pinch too close for the low E or B.
 
#7
It doesn't make sense that you would heve needed to loosen the truss rod, or
at least loosen it that much.
When things don't make sense, it often means that something is not what you
think it is. Do you still have the old string set? Are they really slightly larger gauge
for the E?

And I apologize in advance for this question, in case it's stupid, but are the new strings
tuned up to the same pitch? Tuners can be misadjusted from standard.

(edited to add this)

0.45 mm ( 0.018" ) sounds like a lot of relief for 2 mm ( 5/64" ) action height. That alone
could explain the problem, but it doesn't explain why it wasn't a problem before.

Another possibility is that a fret lifted and is now high, if indeed it was buzz free before with
the same setup specs.
 
#8
Well, Walter, I took that measurement at the first and second frets tonight: there's slightly more than .010" between the string and fret at both points (second-fret measurement taken with the string fretted at the first fret, of course). So the nut's not the issue.

I also did the fret-height check with a metal straightedge: doesn't seem to be anything amiss there, either. No rocking, anywhere.

The buzzing's not horrible now, but it bugs me that it's there. I raised the E string a quarter turn at the saddle (probably best since I have an Xtender key on the E for a few songs in D; even the .107 string I have on the bass now gets floppy down at D), and I'll likely tweak the A string in the next day or two.

Megafiddle: Yep: same pitch (standard E-A-D-G). I don't have the old strings, but they were lighter and lower tension (I'd say by 3-4 lbs/inch) than I'm using -- which perplexes me since I had to loosen the truss rod to get the relief I needed. Then again, this is a Modulus neck, which is pretty stiff, so more truss rod rotation may translate as lesser adjustment than with many other necks?
 
#9
Did you try lowering the relief?
I believe walterw is right about the .010" (.25 mm)

Apparently the modulus neck uses a bi-directional truss rod. That's why there's a region
of looseness; that "bump" is where it begins acting in the opposite direction. There's
no information I can find about adjustment direction, cw or ccw to increase/decrease
relief. I have to guess that the direction is ccw to reduce relief.

Also the graphite reinforcement would require more truss rod tension to change it's bow.
But the extra rotation needed might also be due to a finer thread.

A compound radius is basically a cone surface if the radius smoothly progresses from
one end to the other. But that also means that if you use a radius gauge at the bridge,
the radius there will be larger (flatter) than the radius at the last fret.
Simpler to just adjust the A and D above the fretboard at the same fret where you adjust
the E and G.
 
#10
Thanks for digging up that info on the Genesis neck, megafiddle; I tried here and and couldn't find much info. I'm really relieved that it wasn't at the totally-loose point before (and yes, I can confirm that the rod's a traditional one regarding adjustment: ccw gives more neck relief/bow, cw gives less)

I worked from less relief to more when setting the bass up, and I have to admit that trying less relief to eliminate mid-neck buzz sounds counter-intuitive. But that definitely sounds worth a shot over the weekend -- particularly since the setup when I received the bass had significantly less relief (albeit with thinner-gauge strings).

(Oh: I didn't use a radius gauge for that exact reason, megafiddle. Actually, I don't use them at all; I radius saddle height at the last fret after changing strings, and I re-check/adjust at the same spot after intonation.)
 
#11
VifferMike said:
)
...I have to admit that trying less relief to eliminate mid-neck buzz sounds counter-intuitive.
Click to expand...
That's because it's only half the equation; the idea is less relief gets the strings closer, so you can then raise the saddles to get rid of buzz without the result feeling too stiff.

This and a low nut are all about getting less height behind your fretting hand where it doesn't help the tone, and more height between the fret and the bridge where it does.
 
#13
Fellas, I thought I knew how to set up the guitar. Until I've given my Fender Jazz to my tech (thread on this page) just for kicks.
The instrument afterwards was unbelievable.
The only piece of advice I can give after reading OP: give it to a pro. You can seriously screw up the neck if you keep doing what you're doing - and from what I hear you have very basic knowledge on setting up the instrument.
Cheers!
 

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