If you are interested in some tighter springs, contact Miel Adams, they offer 4 different sets of springs for the Adams Euphoniums:
1) Standard Springs that came with your horn
2)Standard Springs with a plastic coating
3) Tapered Springs, they kinda look like half of a mead spring
4) ADAMS Springs, this is the ADAMS version of mead springs but has no plastic coating, although they have color coated the springs so you can't mix them up.
I am personally using the tapered springs as they are slightly stiffer than the Standard springs and also offer less buzzing since the coils are farther apart, the fourth valve seems slow when held completely vertical, but when in playing position the action is nice and smooth.
ADAMS Springs remove any bounce whatsoever as they are stiff springs, too stiff if you are sustaining for a long time or moving between different fingerings rather quickly. The plastic coated springs do reduce the buzz of the spring to a minimum and to me felt just barely softer than the Standard springs but I did not spend much time with them since I wanted something stiffer.
Hope this helps!
Adams E1 SS, Gold Brass Body .6mm DE Euph N103 Jcup, J9 shank
Meinl Weston 2141 Eb Tuba PT 84