Mandocello buzz: neck relief and string action
I know that we have had strings on this topic before but I wanted to focus in bit on some specifics.
I spend a lot of my time trying to make pleasing sounds on a mandocello -- mostly I play on one that was converted from a jumbo body arch top guitar.
1) The issue: I have been experiencing an annoying amount of buzzing with this instrument. The buzzing occurs most often on sustained chords becoming noticeable as the sound volume begins to “die off”. For example, a chord formation like 0553 (= C major) or one string over 5530 (= F major) the chord sounds great as I strike it but as the sound dies down a profound buzzing occurs and dominates.
I can stop this buzz instantly by slightly releasing finger pressure on the strings – but if I instantly hammer back on the buzzing sound returns. All this leads me to believe that this sound is coming from the strings vibrating against the next frets (below the fretted ones). It seems the buzz is most prevalent on the G and D strings, less so on C and not at all on A. I was wondering if possibly this mandocello might need more neck relief?
2) Measurements: This mandocello already has a relatively high string action with the 12th fret measurements of 0.110” on C and 0.080” on A. I estimate this by the usual method of measuring the distance from the bottom of the string to the top of the fret crown.
I also looked at string clearance under the nut i.e., the distance from the bottom of the string to the fret board at the nut: I measured 0.060” on C; and 0.047” on A side. (BTW this a fretboard has a 9" radius and a 25" scale)
So I then took a look at the neck relief. I measured this by putting a capo on the 1st fret and pressing the string down on 14th (at neck join) -- and working a feeler gauge between the string and the 7th fret to assess the relief. I found 0.008” on C and 0.006” on A.
That seems pretty tight and I'm not sure if that would be considered enough relief or not for strings as heavy as a mandocello?
I wonder if I should try to dial in more relief with the truss? I put a new Stew-Mac two-way hot rod in when I made the conversion so I should be able to make some adjustments relatively easily.
I suggest neck relief is the solution as the string action is already high?
Due to current budgetary restrictions the light at the end of the tunnel has been turned off -- sorry about the inconvenience.