Imagine having a live rig that consists of a couple passive basses, a couple with active preamps, a tuner and a compressor on the board, and then an amp. Let's assume the amp has a button for active/passive padding.
Do you guys tend to use the pad button on the amp? Compensate with a boost pedal with the passives? Change the gain on the Compressor? Something else?
Ideally each bass needs its own gain structure and tone controls. So if you are running two basses, you need two channels. If you don't have enough channels, you figure out the best way to achieve the desired results. This depends on your gear and the way you think.
Here are some examples: I use to switch between upright bass and bass guitar using an AB switch into a single channel amp. Additionally, I need two volume levels for the upright, and it did not have a volume control. I did the best I could to adjust the tone controls for good sound on both instruments. Obviously, it was somewhat of a compromise as upright bass and bass guitar tend to sound very different. I used the amp's gain control and the bass guitar's volume control to manage how loud I played. Not a great solution, but its what I had available, so I made the best of it.
A few years later I ran a single channel bass amp that had an auxillary rack space and an effects loop. I installed a 31 band GEQ in the effects loop. I still used the AB switch to select the active instrument. I also toggled the GEQ in and out of the circuit. I dialed in a basic using the amps controls, and then I used the GEQ to tailor the tone and gain structure for upright bass. This was a pretty significant improvement.
My last touring rig used a rack mixer and a power amp. It was essentially a mini PA system. I switched between upright bass, electric upright bass, and bass guitar. Each instrument had a dedicated channel with gain, EQ, and a mute switch. This was very close to ideal. The channels had bass, treble, and semi-parametric mids. The only thing more I would have wanted was a second band of semi-parametric mids.
As far as whether you should use the active or passive switch on your amp. It may or may not be useful. Typically, the switch does two things of consequence: 1. I changes the sensitivity of the preamp by approximately 7-15dB. The change in attenuation varies by the model of amp. 2. Often this sort of switch has an impact on the amp's input impedance. This can produce a subtle change to the tone and response of an instrument. Passive instrument tend to be more sensitive to input impedance than active instruments. The impedance change also varies by the model of amp. Some input pads change the impedance, and some do not.
IMHO, consult your owner's manual to try and learn exactly what your input pad does.
IMHO Active/Passive is a bit of a misnomer. It's entirely okay to run an active instrument into a passive input as long as you are not getting undesired distortion. I have a fairly large collection of amps, and normally run an active bass unto the amp's passive input. I do have one amp where I may need to run the input pad. The choice depends on if I want a clean sound or a bit of drive.
Good luck!
