Adjusting Valve Cap Tension:
In recent years, thanks to Dave Monette and other
innovators, trumpet players and builders have come to a
much subtler understanding of how very small changes in
equipment can effect performance. Factors that were
once thought insignificant are now understood to have
an impact on the overall performance of the system.
Weight, bracing, interior gap and alignment, hardness,
and many other aspects of trumpet design and
construction are being considered much more carefully
then they were only a few years ago.
One such small factor is the screw-tension on the bottom
valve caps. Properly adjusted bottom valve caps can
improve the response, intonation, and flexibility of the
trumpet. The tension of the caps is controlled with
neoprene o-rings, which are installed on the outside of
the casing, over the threads. Screwing the bottom cap up
against the o-ring compresses it, tensioning the threads
. In order to perform satisfactorily the o-ring needs to
be both thick and of a sufficiently high durometer to
produce the necessary tension. Once the o-rings have
been installed the thread tension of each bottom cap
can be adjusted. Here's how to do it:
1. Install the o-rings on each valve and screw on the bottom caps until they lightly touch each O ring.
2. Adjust each o-ring about a 1/4 of an inch turn. You want the least tension on the 3rd valve, so the adjustment should be complete for this valve.
3. Adjust the 1st and 2nd valve rings another 1/4 of an inch turn. Remember that 1/4 of an inch is not that much! The second valve ring should have the most tension.
4. Now you are ready to test the tension. Play slurring up the harmonic series on each individual valve. When the adjustment is at its best the slurs will feel even and respond without locking on individual notes too laboriously. This takes some experimenting, but when you have found the spot, you will notice a difference in the ease of response, flexibility and pitch center.
Once you have found this subtle spot, the bad news is that you have to do fine tuning on a regular basis. Changes in temperature and humidity as well as the stretching of the rings can change the whole game. A recommended change of approximately once a month will keep you from having over stretched rings.
Some people will appreciate the difference properly adjusted valve caps make more than others. Luckily, this is one modification the player can make himself that is inexpensive, reversible, and easy to evaluate for oneself. We encourage trumpet players to try it.