Duplex, A Grotrian

Ron Nossaman RNossaman@KSCABLE.com
Sun, 11 Nov 2001 10:45:37 -0600


>Ok... i remember last time I looked that the angle up from the capo was around
>12 degrees. Bridge pins were angled at 10. Didnt check downbearing but I
can if
>needed. The angle up from the aggraffes in the bass was a bit less then the
>capo area, but I havent measured that.
>
>Richard Brekne

I didn't see a tenor back scale length, but if it isn't braided, I'd start
there since it's not going to add anything desirable left open and can
provide plenty of undesirable noises if not muted. I'd likely braid the
bass too. Then I'd listen to the result and decide on the next step. If a
next step was necessary, I wouldn't expect any unusual noises from the back
scale in the top two sections unless there is some bearing or plate
clearance problem. I don't know what bearing angles there are across the
first and second counter bearing bars, but you said both sections  are
making noise. I assume they are fairly low. The best benefit from the least
effort, with the lowest penalty should come from braiding or otherwise
muting that 50mm second section. Remaining noises from the first front
duplex should be comparatively minimal then, even with the low angle capo
deflection. If not, you're now in familiar tuned front duplex territory.

If I was rebuilding it, I'd want to increase the bearing angle, decreasing
the front duplex length if possible depending on where that leaves the
string height and angle to the pins.  

I can't say if this qualifies as an answer, but this is how I'd approach it
as a work around.

Ron N


This PTG archive page provided courtesy of Moy Piano Service, LLC