Which input to use?
 

I've got an amp with 2 inputs in it. One of them says active and the other says passive. Normally it would be easy to figure out, but I've got a bass with passive EMG40HZ pickups and active electronics. So I'm not sure whether i should plug into the passive input cuz of the passive pickups or the active input cuz of the active electronics. Any advice would be great.

The passive input is louder, the active is quieter. Since you've got active electronics your signal is hotter, so try active first.

If it sounds too quiet, use the other.

It's not like you won't get sound.

Your amp has a gain control? Use the passive and adjust your gain.

I never understood why my old amp had the PAD and gain control!

I suppose there may be a case where your signal is so incredibly hot that you are over driving your pre easily. For most users, the gain knob should have enough taper to work.

IMHO using the "active" input is a tone such. This is coming from someone that uses a sting ray with the mid knob dimed all the time. I dont over drive the input unless I want to.

I was under the impression that the two inputs had different impedance values...

Most of the time when people talk about an "active" bass they are referring to having a preamp within the bass, not the pickups themselves.

Always use the passive input and set the gain appropriately. If the bass output is so hot that nothing you do prevents clipping the preamp, THEN use the active input.

Yep! This is precisely what you should do. :)

Why? Is it because what someone previously said regarding impedance?

It's fairly common for the gain control to be after the first stage of the preamp, so a hot signal could be clipped before it even gets to the gain control. If you can get a clean signal using the passive input then there's no reason to use the active input.

In any case, active basses don't necessarily give a stronger signal than passives.

Nah. Active basses may be louder, quieter, or the same level as passives. Some passives are surprisingly loud.
Yes. :)
Yes but that's mostly irrelevant. The pad on the active input lowers the input impedance of that jack, which makes it not ideal for a passive bass--it can cause loss of highs/tone. With an active bass that lower input impedance is not a problem, and an active bass also has no problem with the higher impedance of the passive input. So the impedance thing is more of a defect and a side-effect than a feature; and it is ONLY relevant in the sense that a passive bass usually shouldn't go into the active input due to loss of highs/tone.

That's an active bass. But it doesn't need to go into the active input. That input is only for basses that have such high output they cause unwanted distortion in the amp.