Originally Posted by BbbyBld
The same gain setting always works for me whether I'm using fingers, picking, or slapping.
I usually don't crank the gain up too high. It's usually below half way on my amps. I tweak the volume and EQ as needed on my bass while I'm playing if I have to change styles in the middle of a song.
I usually find that I have to turn my bass volume UP when slapping, which may seem backwards, but that's what works for me.
I would hope that you would know (given your job) that the physical knob setting of the gain means absolutely nothing, and varies hugely across amp brands, due to gain design and the gain pot that is chosen (and also due to technique and bass output).
To the OP, you are doing it exactly correctly. If you have a solid state preamp (i.e., not a tube preamp that can actually sound good pushed into a bit of clip), and a preamp clip light, set that exactly as you are. In other words, use the technique that provides the maximum transient peak (typically slapping), and bring the gain down a touch from when you see that clip light come on. When you do that at home, you will typically see that clip light still come on a bit at that setting on the gig, since most tend to dig in a bit more when playing live and 'getting into it'.
So, you are good to go there, that is what the gain control is for, and of course, the setting can change across different basses, and also over time, as you refine you slap technique so that there should be very little difference between the tone/volume of your slap and fingerstyle signals (other than the more aggressive initial attack of the thump when slapping).
The other thing to realize when you slap (and this is why so many use slap style when testing rigs) is that the initial strong peak of a thump when slapping can driver a power amp to full power, regardless of the master volume setting, and can also push a driver past its mechanical spec limit (that 'xmax' that many mention on this site). So, sometimes you will actually notice a drop in volume and low end when you slap. If that happens, and you have the pregain set correctly, that can either mean not enough power, not enough cabinet, problems with technique, or a combination of all three.
Finally, you will know that your 'slap chops' have arrived when you can seamlessly go between fingerstyle and slap without adjusting anything. One of the best ways to practice/improve slap style playing is to do your scale exercises using slap and then fingerstyle and then back to slap. In other words, do a major scale in a single position first fingerstyle and then with your thumb. When you achieve the same tone and volume (with only that peak initial attack different) and time (!), you know you are there. If you are significantly losing low end between the thump and fingerstyle, or find your thump louder than your fingerstyle, that can translate to problems on stage. IMO!