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fiddlercrab3
Dec-27-2008, 9:56pm
Hi everybody,

My name's Rob. I'm a college kid who started playing mandolin freshman year in the university's Bluegrass Ensemble. I've been playing violin for most of my life, so mandolin was an easy transition. However, my violin/mandolin instructor is currently on sabbatical this year. I have a different violin teacher, but no mando prof as a result. I'm turning to the Cafe for advice.

I have a mandolin on loan from my school that I've been trying like hell to keep in tune, but I can't get the 12th fret to match the harmonic: while the A and E strings match pretty well, the D and G harmonics are about a quarter tone flatter than the fretted note.

As a violinist getting acclimated to frets, this is frustrating. :) A buddy suggested I should adjust the bridge, but I have no clue how to do so properly. I messed with the positioning of the bridge a bit, but to no avail. It may also just be a lousy fret job; it's a school loaner, dig? :mandosmiley:

Any general advice for how to properly align the bridge? It's an Epiphone MM30BK, made in Korea, serial 59050007, if that helps at all. Neck is not adjustable.

Thanks MandolinCafe community! I love this site, and I've learned a ton. I would also appreciate any and all advice from other violinist-turned-mandolinists. Can't wait to hear from you!

Best,
Rob

mandroid
Dec-27-2008, 11:44pm
FAQ, as it is , you will learn much with the Search mentioned in the bars above.
welcome , ..

Fretbear
Dec-28-2008, 12:11am
Hey Crab, welcome to the Cafe.
With your experience, you should be able to handle doing it yourself if the bridge is properly fitted to the top to begin with, (which is a big if) and that effects the tone and volume anyways rather than the intonation which is what you asked about. To set the proper intonation, you need to use and remember the FLAT rule:
F(retted note) L(ow), A(way) from T(ailpiece)
The fretted note is referring to the twelve fret octave or harmonic note. This note must exactly match the corresponding open string. Remember that on a mandolin as on a violin, the bridge is not fixed to the top and is only held in place by string pressure. The easiest method would be to get a hold of some kind of accurate electronic tuner and then replace the outer E and G strings with new ones and start to try matching the octaves of the high E to it's open string and the octave of the low G to it's open string. You might want to remove the inside D and A string pairs while you do this, to allow you to easily shift the bridge base position and because you should put a new set of strings on anyways afterwards if you really want to hear it play in tune. There is not a whole hell of alot that you can do yourself about the intonation of the D and A strings once you have set the outer G and E strings, without working on the bridge, but they will often be where they should be if the outer two are in their right place. Remember not to remove all of the strings at once or the bridge will fall off of the mandolin which is the opposite direction that you want to go. One other point is that when you are finished, the bridge saddle where the strings actually contact the bridge should be in an upright perpendicular position to the mandolin top and not pulled forward towards the peghead. The new strings should also not be too light or they will not stay in tune well. Gauges of .040" for the G to a .011" for the E are considered pretty standard if the instrument is not too lightly built. Good luck.

Ivan Kelsall
Dec-28-2008, 1:41am
You might also try angling the bridge so that the D & G string slots are closer to the fingerboard,this shortens the string length & should raise the pitch sufficiently to give you the correct 12th fret pitch. If this doesn't work,i'd be looking for a top quality bridge with the correct compensation. You could get someone to help you check the fretting accuracy as long as you know the 'scale length' of your mandolin,at least you'd know if there was a fundamental fault with it or not,
Saska

fiddlercrab3
Dec-28-2008, 4:14am
Howdy Mandroid, Saska, Fretbear,

Thanks for the tips. I've messed with the bridge a bit more, and it seems that I may just need a new bridge. Regardless of the angle I put the bridge at relative to the fretboard (e.g. angling the D and G closer to the frets), the intonation problem persists. I had a different result when I slid the entire bridge, but it seemed to contradict the FLAT rule: when I moved the bridge much closer to the tailpiece, the fretted note would be sharper than the octave harmonic. I've found a decent balance where it's pretty close, but I'm guessing a faulty bridge is at the heart of the matter.

Good call on the lean, Fretbear- I took a look and it seems the bridge tilts forward a bit when viewed from the E-string side. The strings are standard J74's, so that shouldn't be a problem.

I realized after posting that the flatpicker who's running the Bluegrass Ensemble in lieu of my teacher plays some mandolin too. I bet he could help. I'm on break for now, but I'll try to get some lessons together too. As a quick follow-up question, how do mandolin bridges compare to guitar bridges?

Thanks for the help,
Rob

Fretbear
Dec-28-2008, 5:20am
Thanks for the tips. I've messed with the bridge a bit more, and it seems that I may just need a new bridge. Regardless of the angle I put the bridge at relative to the fretboard (e.g. angling the D and G closer to the frets), the intonation problem persists. As a quick follow-up question, how do mandolin bridges compare to guitar bridges?

It is quite likely the supplied bridge is garbage. The problem could also be with the nut or fretboard.
Mandolin bridges can be of different types, but the ebony Loar-style adjustable bridge is the standard.
They are quite drastically compensated compared to a guitar saddle or violin bridge which have almost none.
It is even possible that the saddle is installed backwards. Look at Paul Hostetter's post #37 on this thread to see what a proper bridge should look like and how the compensations are oriented.
http://www.mandolincafe.com/forum/showthread.php?t=40193&highlight=bridge+compensation&page=2