A:Without seeing and hearing an instrument, of course we cannot diagnose the specific issue of an instrument (any instrument) and its action, But here is some general information …
(1) First, it is a fact that little tiny strings wiggling in a magnetic field create a smaller signal than great big ‘ol strings wiggling in a magnetic field. The mass of tiny strings is smaller and so it disrupts/alters the magnetic field less. Also the swinging of a big string is somewhat larger than a smaller string, I think, so its wiggling is both further and more mass.
(2) So the first line of approach on the instrument is to see if you can get the magnetic field to be closer to the small string, because as the magnetic field grows closer, within certain boundaries, the magnetic field reacts to the wiggling string more.
The general way you do this is either to (a) raise pole pieces under tiny strings, if you have pickups like the gold-case pickups on the Dragon instruments, or if you have pickups like on the Chapman Stick, or (b) if you have rail or solid pickups then you adjust the mount screws so that the end of the pickup under the small strings is closer to the string.
One good way to do it is to bring the pickup high until the string strikes it when playing at fret 25. Then back it off. Now when the string is very close, the magnets will pull on the string, and it will have a slight distorted sound. (Depending on your rig, this may be subtle.) Back the pickup away until the distorted sound just diminishes.
The other way to approach this is to move the other end of the pickup away from the fatter strings. Because it’s the difference in closeness that makes for a difference in volume output from the thinner and fatter strings.
In the Mobius factory shop when prepping instruments to go out, we test the relative loudness of bass strings at fret 3-4, and the relative loudness of melody strings at fret 13-14, as a good general overall test.
(3) The other part of the equation is — what are you playing the instrument into? If you run it into a bass amp, the nature of a bass amp is to be very kind to bass strings, but it will absolutely eat up your highs, and tiny strings have very little sound t offer other than highs, so their volume is naturally diminished.
Likewise the tone control, if your instrument has one, if it’s rolled off will kill more sound on your highest strings. The Chapman Stick instruments don’t normally have tone controls, but Warr Guitar and Megatar instruments do, of course, because it gives you more control over your sound during the gig.
In a similar fashion, on any amp, your EQ settings create a large difference in what frequencies come out. In our factory shop when we set up instruments, we use an unusually flat-response P.A. type amp (Barbetta) with no boosts nor cuts in the EQ. We don’t want to hear the sound sweetened or colored in any way when we’re setting it up. But of course, for your music, you will choose the amp and effects which best present the music you are creating.
And also, some effects (even when not labled EQ) change EQ in order to accomplish their effect. Phasers and chorusers can cause phase cancellation, and some distortion effects boost mids (at the expense of highs).
Try carrying your instrument into Guitar Center and try other amps. They will all present different sounds, including a difference in the relative volume between high strings and low strings.
One favorite sound, for many of us, is a ‘jazz guitar.’ But it’s also a fact that this distinctive sound is created by rolling off highs, and so to compensate, your fingers have to be lighter on big strings, and heavier on little strings.
(4) The action of strings does absolutely have an effect on relative loudness. If you have a relatively low action, and you have the gain up, usually a good balance is available.
Sometimes overlooked is that, if you have a high action, then you have to hit all strings hard, and this gives you very little control over dynamics. So how could you create, with your fingers, more volume from the high strings? You can’t.
With a nice low action, and the gain turned up a little higher than seems reasonable, then you can play lightly, and your fingers will have far more control over how loud the strings sound.
Although tiny strings absolutely make less sound than fat strings, and that continues to be true for any guitar or bass, all these other things will affect the volume that you hear.