Weird Intonation Issues

[Nonprophet]

Recently picked up a used/like new Eastman Octave Mandolin. I played it for bit before buying it, sounded great--in tune and good sound quality. I did feel the strings were a little "clangy sounding," but I bought new strings and took it to a local luthier for a good setup and change to lighter strings. Once I got it home from the luthier, I was surprised and disappointed that the A strings were noticeably sharp. I'd tune the mandolin, but when playing anything up from the first fret the A strings--and only the A strings-- were badly out of tune. I took it back to my luthier, he listened, and agreed there was an issue--and he concluded that the bridge saddle should be replaced. He very kindly agreed to make me a new one, and explained about how most saddles are made somewhat generically to fit a variety of instruments, string gauges, etc. and he felt that replacing the saddle would solve the issue.

So, he made and installed the new saddle, and I picked it up today. He strummed a couple cords and it sounded great. I get it back home, and a few hours later I take it out of the case to play it--and the A strings are badly out of tune (sharp) AGAIN. All the other strings sets sound just fine, but the A strings are noticeably off.

I'm just really perplexed why it sounded fine when I played it before buying it, why going to a slightly lighter string gauge could cause an intonation problem, and why after getting a custom-made saddle, the problem persists. FYI: The strings that were on it were D'Addario Medium EJ80's (according to previous owner who left the empty string pouch in the case) and the new strings are D'Addario EJ81's.

Any ideas on what could be going on here?

Many thanks.

[Rob Meldrum]

If the A strings are in tune when played open, and are sharp as soon as they are fretted, the initial problem is with the nut slots. The slots should be cut so that they point downwards toward the tuning pegs. This assures that the strings break cleanly at the very front of the nut.

Once you have addressed this if you still have an intonation issue with just those strings, then you need to gently file the bridge back, just where the A strings cross the bridge. I'm assuming the intonation is spot-on for all of the other strings. File back toward the tail of the mando, re-string and check the intonation. It only takes a minor adjustment for a big change. This is not very common... I think you'll find that once you fix the nut slots you'll be fine.

Email me at rob.meldrum@gmail.com for my free ebook on how to set up a mandolin and put Mandolin Setup in the subject line. The concepts work for other fretted instruments.

[jimmy powells]

I totally agree with Rob. Have a VERY CLOSE look along the NUT. Apart from the fact that the slots should be cut as Rob describes, I wouldn't mind betting that the A strings are actually a little higher than the rest. They should go with the camber of the fretboard. If you've had it to a luthier then for certain he should have made the bridge top further back as Rob says so more likely the problem is with the nut. You'll be surprised how low you can put the slots and not have buzzes, providing you have just the tiniest amount of relief.

Another consideration is that the lighter the strings, usually the more itonation issues you have.

[Hearth_man]

Yep, I agree. That is a nut issue, not bridge.

[jimmy powells]

I set up an Eastman octave mandolin for a friend a couple of weeks ago and happened to notice something very unusual. Normally the bridge top has E and D forward and A and G back. This original bridge top was not like that at all. From memory it was something like the A string FORWARD and the E back and possibly similar on the bottom two. I assumed it must be right and perhaps something t do with 2nd strings being covered.

Worth having a look at the original bridge top out of interest.