In trying strings that suited son Viohazard's violin, the A string was the hardest to figure out. Seemed weak and dull No Matter What.

But then...found that the bridge was tipped over just a little, and while it's still not perfect, that made a huge difference to the A string.

You'd think a drunken bridge would affect the D string more, as it sticks up higher, but maybe the thinner A string is more vulnerable?

Posted this just in case anybody else is dumb enough to spend ages puzzling over the same problem!

It may be because a leaning bridge means that the feet will not be in proper contact with the body, and the A string is nearer to the foot on the soundpost side.

Just guessing! But I know from experience that fractional adjustments of the bridge can make a huge difference to the sound.

Might the soundpost have shifted? A knock to the instrument, even in the case, can somethimes just be in a way that will disturb the setup.

If you have straightened the bridge and there seems to be no other visual cause, a trip to a luthier might be advisable.

I assume the strings are changed (as an entire set) on a regular basis?

I did get the luthier to fix the bridge and also check the soundpost, because (I am ashamed to say) I actually got him to put on the new set of strings for son's exam, as he had been sick and I thought it would take him an ice-age or two to change them himself.

As well as setting the bridge upright, he did gently flick the E-string end of the bridge so that it was not resonating quite so loudly over the E-string, making it more balanced with the A string.

P.S. The luthier has a son the same age as Viohazard, and kindly changed them without charging.