Weird Distortion Sound

Mandobart

I play an Altamira M20D built in 2007 that I got through this site, about a year and a half ago. Set up by Joel and really plays and sounds nice. Lately I've noticed a strange distortion-like sound. It is very evident when I play a D note on the B string or the 12th fret harmonic on the D string (587.3 Hz). Less evident at lower freqs. I changed the strings, double checked the intonation, tried leather strips under the tailpiece (which did help reduce the sound) and laced some leather through the strings between the bridge and tailpiece. But I can't completely eliminate it. I checked the tuners, tailpiece, etc. but couldn't find any loose hardware. So I'm thinking maybe a loose brace or something inside. Anyone else ever have a similar problem and ideas for a potential solution? No real pro level luthiers in my immediate area; and it's about 4 hours back to Joel's.

Scoredog

could be where the side part of the bridge is glued to the guitar, or could be a brace. Hold down the bridge part when picking and see if it changes.

Bones

Yeah what Scoredog said. Check if one of the side moustache pieces is loose (not securely glued down to the top). A lot of guitars these days just have them held on with double stick tape and they can come loose over time.

Bones

Also had that happen with a bad set of strings but you changed those so unlikely that both sets would be bad I would think.

AmundLauritzen

Every time I had buzzing it was the moustache pieces or the action was slightly off so that a string touched a fret somewhere. The action was easily remedied by placing a wooden veneer under each side of the bridge to raise it slightly.

I taped my moustache pieces to the guitar with painters tape. It's this blue tape with a kind of glue that doesn't damage the finish of the guitar.

It doesn't look particularly aesthetic, but at that point I got sick of gluing them back on, because you need to apply a very small amount of glue so that the moustache pieces can be taken off if you need to reposition the bridge. But that also means they come off again pretty quickly. If they're glued into place and you can't remove them, well then it's going to look strange when the bridge is moved and the moustache pieces don't align properly.

Hemert

Y'all should just switch to fiddle, easier to carry and no glue needed.

Jazzaferri

Scratch scratch

Mandobart

Thanks all for the suggestions. For Hemert's benefit I'll report I have no weird noises on any of my fiddles. Moustache pieces are on solid. I did work the tailpiece more, however. I took a longer, wider piece of leather off an old mandolin strap and twisted it to make it thicker, then carefully worked it under the tailpiece with the strings slacked. When I tuned her back up, the noise was gone.

Chiefbigeasy

My weird harmonic sound came from a loose rattling truss rod. Snugging it up a little--in either direction--did trick.

crookedpinky

My odd noise came from a loose wooden tailpiece insert.

Jeff Moore

Two unmentioned sources of weird harmonics: When your bridge and top don't meet flat. it's usually easy to diagnose, Just put your guitar between your eyes and a light and look for light between the bridge and top. It's that easy. Remember the whole foot of the bridge doesn't have to touch but any part of the foot that's real close but not touching is suspect. Before I began to sand bridges down every time I made one, I got some outrageous (unpleasant) sound out of ill fitting bridges.
Another unlikely but easy to diagnose problem is tuning machines. If you get your ear real near them and create the sound (yoga), you can at least eliminate this as the source.