What is a Preamp?

[crunchnasty]

What is a preamp and why do I need one? I'm looking into getting a single 18" cab and a cab with two 10"s in it. What kind of power would I need and what are some good recommendations as far as equipment goes. I'm buying a Traben 5 string, thinkin Ampeg 18"s and 10"s. Any help would be much appreciated.

 

[i_got_a_mohawk]

A preamp boosts the signal of the bass so that the signal can be used by a power amp, the power amp as you probably guessed "powers" up the signal to a level that means it can push the speakers in the cabs

You need a power amp aswell as a preamp, what are classed as amp heads are a preamp and a power amp in the same unit

Preamps are also the part where you can alter the EQ of the signal etc

On the question about gear

What kind of music are you going to play?

What size of venues will it be in and what size of band?

(personally i dont like 18"'s too slow, i dont even like most 15"'s tho)

 

[PB+J]

A preamp takes the very low signal produced by pickups and boosts it to a level the power section of the amp can use effectively. It's also where the signal can be harmonically shaped--bass frequencies emphasized or cut, treble boosted or cut, etc.

You don't have to have a preamp. You can run any bass directly into a power amp. You just might not get as much volume or signal clarity/range as you would with a preamp, but it'll make sound. I've done it, and I found that with my passive j-bass I got less volume, less lows, and less highs. But it was usable.

If your bass has a preamp onboard (an "active" bass), then you really don't need a second preamp. If the bass needs a battery, then it's got a preamp in it. You could run the bass directly into the power amp. Most people don't, but there's no reason why you couldn't.

Snce I play only passive (no onboard preamp) basses, I find I like a preamp to boost the signal to the optimum level. A good preamp really adds a lot to the tone. I use a preamp that sends a signal to a power amp and another to the PA system, and that gives me some simple tone shaping

 

[oldfclefer]

A preamp is, as stated in previous posts, a component that raises the signal level and, in most cases, provides tone adjustments.
What type of preamp is best?
If you buy a solid state amp, a lot of bassist prefer the sound that a tube preamp will add to a solid state amp. A tube is old school technology which employs a vacuum tube in the circuitry instead of a solid state transitor to amplify the signal. Tubes definitely change the sound of the signal from the clean signal of a solid state output.
Most bass amplifiers on the market are equipped with a preamp. Most have a "power amp in" input which bypasses the amp's preamp so that you can employ an external preamp.
Many manufacturers produce "hybrid" amps which usually have a tube preamp and a solid state amp. Some are "all tube" which means that both the preamp and amp are tube-driven. Of course there are all solid state amps too.
Which is best? That's for you to decide. Plug in and try every combination you can before you make a final decision based on sound, price etc.
I've owned all solid state amps that sound great. I'm using components at this time, and they sound great too. My acoustic/electric bass has its own preamp, but I minimize its output and use it through my component system.
Certainly the recommendations given here are a great way for you to zero in on the best components available.
I use an Alembic tube preamp with an Ampeg amp.
Your choices are literally endless.
Have fun finding the right setup for you.

 

[PB+J]

I would also avoid 18 inch speakers--they tend to get mushy. I like 12s myself, a compromise between the tight fast sound of tens and the old school sound of fifteens