It's hard to talk about SB2 tone without dancing around "subjective" hearing the entire time, but as I understand it, and as G&L explained to me personally, the SB2 tone knob was added due to "customer demand", not because G&L felt it necessary.
In fact, they don't feel it is necessary, which is why it's only an option.
Current owners looking for that setup can either drill their pick guards or stack pots. I've done both mods many times... and I like to push stacked pots, because there are so many really cool stacked pots out there, which really open a lot of doors... mostly off the beaten path.
The only reason that I stress these issues with the SB2, is because I wasted 3 years of my life, trying to make them sound the way that I wanted them to, and I was grabbing at air. I'd hate to see anyone else go through what I did. Meaning...
If they're unhappy with the tone of the SB2, I think it's very unlikely that the "tone knob" would be their savior... However, if you love the SB2 tone, you might like what a tone knob can add to it...
Of course, the tone knob won't add anywhere near what the tonal options of the amp can provide either. Not saying that any of this applies to you.
I just always put it out there, because it breaks my heart when I here anyone with an SB2, wondering why they can't get it to sound like a P... or searching for better tone.
A lot of people have the SB2 and adore it... So do I, and I wanted it to be the last bass that I ever bought. Unfortunately, I wanted to sound like a P, and to me, it did not. Which in my opinion, is why G&L brought back the LB100, and why it's soooo successful and popular.
just my two cents
I was just amused at my response when presented with the actual facts. 
). But no way. Maybe it's the age: three decades vs three months. Or maybe it's the strings: TI vs Fender. But I would have to work pretty hard to make one cop even one of the tones of the other, let alone most or all.
