Good luck and I think you are right in raising the nut.

Matt is correct in his pointing out that raising the nut (or zero fret) has benefits in achieving the lowest overall action.  Someone has done the analysis to prove that raising it about 0.005 from dead flat allows for keeping the action lower at the saddle.  To that end, I use a zero fret that is about 0.005 higher than the jumbo frets on the rest of the fretboard.  One of the advantages of the bolt on neck that I use is that I can adjust the spacer under the zero fret to fine the action a few thousandths up or down from there as required during setup.  The rest of the fretboard is flat when the strings are not at tension.  Under tension the fretboard bows very slightly, perhaps simulating the curve that Dwain explained.

Thanks all for your generosity in sharing suggestions. Can't wait to get started!

At the risk on being a contrarian, I have had good success with keeping my dulcimer from going sharp as you go up the frets a different way that also helps with the bass buzzing problem.  Rather than focusing on the saddle height, I find adjusting the nut or zero fret slightly higher allows me to keep a more consistent and lower action across the fret board.  Yes, definitely, it sounds like your saddle is too high.  When you get that resolved, and if you are in the mood for even more fine tuning, try raising your nut by maybe 10% and see if you can adjust your saddle down about the same percent.  As with any adjustment, your mileage will vary.

Some builders do build flat fretboards. When there are as many frets as the dulcimer has, though, the problem of getting the lowest action becomes very much like that of designing auditorium seating.

Imagine an auditorium in which the seating floor is flat: even if everyone is the same height, people will have trouble seeing over the heads of those in the next row. And in the foremost rows (that cost the most to get), you begin to see less and less of the performers!

So the answer is to make the floor a long sweeping curved surface sloping gently down, each row a little lower than the one behind. That works well until about 2/3 down toward the stage: at that point the person in the next row are no longer the issue. Now the problem is that you can't see all of what's happening on-stage. So the floor has to start to rise so each row is a bit higher than the one before. Then each person can see everything on the stage.

So think of the string's "line of sight" as it is fretted at each fret, and design your fretboard so that, at each fret position, the height above the further frets is equal. If you're good at trigonometry you can solve the problem as one of the string forming a constant angle when fretted at each angle such that the sine of the angle is just a bit greater than the top of the next fret's crown. Since the distance between frets is exponential, that fretboard surface will be very interesting mathematically. (I've never done it mathematically. I prefer the heuristic method in instrument building, not analytics —except in the matter of setting frets in equal temperament).

That's a great idea! just remember to replace the nut with a packing piece so it is level with the fingerboard before starting.

Every dulcimer will have its own fingerboard 'profile,' meaning a concave 'dish', though some makers prefer to build with a flat fingerboard, I hear.

For what it's worth, I set the nut height at .015" higher than the fret crown I'm using. That seems about right for the way I profile the fingerboard.

Three dimes seems like a TON of extra height by the nut. I hope that isn't due to warping or bowing.

If you have a nice straight edge on a metal yardstick or something like that, you could set it along the fretboard and observe if the straight edge touches all the frets, or if some of them are lower/higher. It is possible that some frets have risen slightly out of their slots and need to be 'tapped' back into place.

It can be helpful to check each fret with a tuner and note how out of tune each fret is. If the first couple of frets are the most out of tune, the issue is most likely your nut being too high. If the frets get more out of tune as you get closer to the octave, you most likely need to move or reduce the height of your bridge.

Once the frets are all level and the action is correct, you will most likely have to readjust your bridge placement anyway. 
Tune the string up to tension and get it exactly to the desired note. Use a tuner to compare the open string to the note at the 7th fret (octave) If the octave is  flat, the bridge needs to be moved *closer to the nut* If the octave is sharp, the bridge needs to be moved *away from the nut*

Yes, I wasn't quite clear on that was I? The dime is place on the fret board. The nickel is placed on top of the fret.

Ken

"The dulcimer sings a sweet song"

[/quote]. A set of number drills (1-60) is great for this, since each drill is a very small variant of its neighboring drills' diameter. So remove the bridge and substitute a number drill. [quote="Dwain Wilder"]

[/quote] 

Thanks for reminding me of this Dwain. I think you either mentioned this to me some other time or you wrote it somewhere and I forgot all about it. I think this is a very sensible way to adjust string height. I appreciate your sharing it again.

Ken

"The dulcimer sings a sweet song."

Can you specify when placing the dimes or nickels- the coins should be placed on top of the fret, right? (not on the wood of the fretboard surface between or next to the frets).

This is genius. What about the nut? Remove that and replace with a closely sized bit, too?

I agree.

One way to finalize the optimum action height the dulcimer is capable of is to find out the minimum saddle height at which the bass string doesn't buzz, then add .005". A set of number drills (1-60) is great for this, since each drill is a very small variant of its neighboring drills' diameter. So remove the bridge and substitute a number drill. Intonation doesn't matter for this test of course, but you do want to be tuned to playing pitch.

Pluck the bass string at each fret forcefully (sideways, not vertically). Substitute the next smaller or larger drill bit shank, depending on whether you find a buzzing fret. If you find a buzz on only a single fret, consider dressing that fret crown down a bit. After you've found a drill shank that represents the minimum action height on the bass, check for buzzes on the other strings. That's a check of the whole fingerboard's surface regularity, and the possibility that some frets aren't well seated or have worn or grooved crowns.

@ken-longfield Great info, saved for future reference, thank you

@dulcimaryland Looking for ward to hearing your results and experience. 🍿

Thanks, Ken. The action is significantly higher than that; I could probably put 3 dimes!

This is a great place to start 

The first thing I would do is check to see that, if the bridge is moveable, it is in the right place. If it isn't moveable, checking the action is a good start. A general rule of thumb is that the strings should just touch a dime when placed next to the first fret. I place the dime on the side toward the second fret. Then place a nickel on the seventh fret and the strings should just touch the nickel. If that adjustment doesn't work, then I would calculate the proper fret spacing for the vibrating string length of the dulcimer. Some programs let you print out a template. I would use this to check the fret spacing and re-fret if necessary.

Ken

"The dulcimer sings a sweet song."

I have an old dulcimer, 1977, which has an intonation problem. It frets sharp. I'm handy enough that I'm willing to attempt to fix it myself. I suspect that if I lower the action, it might fix the intonation. Am I on the right track or is my only option to adjust the distance between the nut and bridge?