Yep -- some instruments (seemingly identical to others of the same model by the same maker) just seem to want to be in a certain tuning; others will swap tunings and sound good in all of them.  Whether it's internal instrument volume, strings of differing sizes and tensions, tensions on other parts made certain ways or what; your guess is as good as mine.  

Related to my original question, I've been trying different tunings, and especially different combinations of notes, high or low, to see how the instrument reacts.  It appears, at least to my ears, that the problem with the melody string sounding sharp or flat disappears somewhat the higher I tune the strings (at the moment, 12, 14, and an unwound 20).  Presently in DAA, with very little problem noted, and I think the instrument sounds better there, than my original CGG, and definitely better than if I try to go any lower.  I don't know enough about sound dynamics, but I do know from guitar playing that there is sometimes a "sweet spot" in the way of string gauge and tuning on any particular instrument, depending on size and wood used.  I believe the dulcimer top on this one is spruce (see attached photo).  Am I on the right path, here?

As mentioned earlier, I can't lower the bridge at all, and my work on the nut appears to have given the strings at that end a somewhat decent height.  Thanks

dulcimer-b.pdf  •  429KB

Better to take material off the bottom of a nut or bridge to reduce height.  Deep notches can "run into each other on the top"...  Search on here on the phrase "nickel and dime" and you'll find descriptions on reducing string height to a good level.

Thanks (again) Skip.  I was able to deepen the nut notches, and the action is a bit lower on that end.  Tried to do the same on the bridge end, but there isn't much area to work with.  Splitting the difference, as you describe, seems to be the way to go, here.

Changing strings or tuning isn't going to do much. The problem is the extra height causes the tension for the length to be too much. What may help is to lower the nut [or deepen the notch a bit], make sure the string is touching the bridge as far back as possible and kind of split the difference between sharp/flat [open/affected fret]. It should be ok to be on the slightly sharp side rather than the flat side as flat is annoying and more obvious. If it's less than about 10 cents [usually in the green on the tuner] it is probably acceptable to most folks.

Here's a photo showing the string height.

dulcimer1.pdf  •  106KB

Now that I'm sort of getting used to the wooden tuning pegs, I've started to notice that the melody string on my 1969 hand built dulcimer is always sharp when I use the noter (28.5" VSL, staple frets only under the melody string).  I've tried easing up on the noter pressure, which helps a bit.  If I tune the string down just a touch (slightly flat) it sounds better anywhere up the fretboard but when played open.  Problem is the instrument seems to have been built with a high sitting bridge (which I assume is causing the string to go sharp when pressed at the fret). The bridge of course cannot be lowered except to cut down the end cap holding the bridge (which I wouldn't do).  The bridge itself is about as low on the end cap as it can go, sticking up just slightly.  The nut placement is ok - if the bridge were at that level, there wouldn't be a problem.  The action, from the top of fret to string, is - first fret 1/16, middle 1/8, last fret 3/16 (all approximate).

Any ideas?  Go heavier or lighter on string gauge?  Different tuning (CGG at the moment)?  Thanks