Pre-amps are pre-amps, location is a matter of preference or convenience.
Preamps are there to EQ or color your tone. Don’t need it though. Your amp has a preamp in it, along with some EQ generally. Preamps everywhere!
You don’t ever ‘need’ a preamp, unless you want it to color your tone in some way.
James Jameson never had one, nor McCartney.
Short answer - yes. @howard can speak very intelligently here, but, yes.
EDIT on preamps.
There are zillions, and they all have their own take on how they color your tone (or don’t, my amp has a very very clean preamp in it, on purpose).
I have two preamps on my board. VT Bass DI and a Darkglass B7K. They both have EQs and distortion circuits and even cab sims, but are very very different. B7K is more modern sounding, the VT Bass DI simulates the old Ampeg SVT amps and the Ampeg B15N, both originally tube amps.
The tone rabbit hole is a very deep one.
But if you step around it, you can play all day and never be the wiser.
Amps are far from required. Haven’t owned one in years, don’t miss it.
The SansAmp line of products is named that for a reason
Those were actually excellent questions, not bad ones at all!
As with most things music related, there’s no right or wrong answer here. Some people love amps and like to do that route. Others play through PA’s or monitors and use other approaches (preamps, amp sims, etc) to get the amp-like tone. I’m definitely in the latter camp.
Preamps - never required, but always good for adding tonal control. Almost everyone uses one, if only the one built in to their amp.
I like to look at preamps this way:
The preamp on the bass (if any; if not, the tone control) - this controls the sound output of your instrument, before any other pedals or processing.
The preamp pedals can add tonal control at different points in your pedal chain, and the placement can make a difference. Usually you want them last as that’s where a lot of people have their DI, but this is not mandatory.
The preamp on your amp controls how the overall sound is EQ’d for the environment you are playing in. This can often require EQ tweaks. Additionally, in modern Class D amps, nearly all of the tonal characteristics of the amp come from the preamp.
But these are broad and flexible distinctions, not hard and fast rule. The only real rule is: if it sounds good and is a good workflow for you, go for it!
However, to get there, there often is a learning curve. Here, it is important that you know what all the components in your signal chain do (or not do) in order for you to be able to get the result you want.
For some of us, this is best accomplished starting with a very clean amp/pre-amp and then adding components one at at time (often in the form of pedals) that add color or “texture” to the clean tone according to your preferences.
Others do all this with hardly any physical components, but mostly plug-ins.
Be prepared to experiment. And spend a bit of money in the process…
You’ll want to try a bunch and see which you like. I don’t own any PA’s myself but have looked at some. The Yamaha DBR12’s look good to me. Their frequency curve bends at about 52Hz which will sound good, even though it starts to cut in to the lower notes on the bass; that’s usually a good place to start EQing/filtering away the low end to trim out the mud. You could always add a PA subwoofer if you wanted.
My studio monitors have about the same response and sound great. You would want to front them with some kind of amp/cab sim.
You can also go cheaper; there’s a bunch of 750-1000 watt powered PA’s in the $300 range.
Lots of people play through venue PA’s without issue.
If you decide to go this route you’ll want to put in some thought in to things like mixers as well; you can run multiple instruments and vocals through a PA. This is the main driver for why I would go with a PA and not an amp, as I would have keys, guitars and vocals to worry about too. PA’s are a good solution then as we would only need two instead of a bunch of amps to lug around.
If I were only worried about amping my bass, I’d stick with a bass amp.
Remember that PA speakers are just speakers too. They will be limited the same way a bass cabinet is. If the PA only has an 8” woofer, it won’t sound like a 4x10” or a 12” or a 15”. You can think of a PA like a bass amp that also handles the upper ranges of instruments better. For that reason a PA with the equivalent low end quality (or sound output) to a particular bass amp is likely going to cost more.
i have never been a fan of stacking preamps. you have (active) tone controls on your bass (which technically is a preamp) going into an eq/preamp pedal going into the preamp on your amp… i can never figure out what is shaping what anymore.
now of course not everyone has all these but i personally like to try to get my signal as flat/clear/non-colored as possible (i.e. set everything to flat) and then shape that with one preamp (tone coloring) source that i prefer so that i know exactly what is coloring the signal and how it’s doing it. and of course then into 15 bazillion pedals to further change it
I agree with this too. It’s hard enough to learn what one set of knobs do. Adjusting stuff in more than one place also gets more difficult to get back to later.
I also appreciate @howard’s method of getting the sound he wants with one set of knobs (thinking of them as part of the core instrument sound) and then using another set to correct for problems that show up in the actual performance space.