The technical explanation
Shubb Capos work on an "over-center" locking principle. If
you've used one, you know the feeling. As you close the capo onto the
neck, it passes through a point of greatest resistence (the center),
then relaxes somewhat into its locked position.
We've made up a name for the the difference between the
amounts of pressure applied at these two points; we call it dropoff.
More dropoff means a greater difference between
pressure encountered as it passes through center, and the pressure applied
in the locked position. Less dropoff means a lesser difference between pressure encountered as it passes through center,
and the pressure applied in the locked position.
Offhand you might imagine that the least amount of dropoff would be best, but that's not
exactly the case. If you have too little dropoff, the lock is less secure
and there is a risk of the capo opening accidentally. But if you have
too much dropoff, too great a force is applied to the guitar neck while
closing, and there could be too little pressure applied in the closed
position for the truest tone.
So you see, there is a JUST RIGHT amount of dropoff that makes for perfect
Another benefit of dropoff.
It is a well known fact that if a capo is too tight, it can stretch the
strings out of tune. Most players understand that there is a "just
right" amount of pressure for best capoing, too. The
dropoff in the closing action of the Shubb capo serves as a built-in safeguard
for those players who are not clear on this concept, and who might have
a tendency to over-tighten a capo. In other words, it prevents the unwise
user from putting his guitar out of tune by not allowing him to bring
the capo to rest in its tightest possible position.
While this feature of the Shubb capo is not especially obvious to most
users, it does in fact contribute to the Shubb's excellent reputation for
not causing tuning problems
On the original Shubb capo, the dropoff increases at the smallest end
of the capo's range, and decreases at its widest end. In other words, when
used on an very thin guitar neck, the dropoff effect is exaggerated. In
the extreme, it could result in insufficient pressure on the strings when
engaged. On an unusually thick neck, the dropoff is minimal. In the extreme,
it could result in an insecure lock, or too much pressure on the strings