Errrr I'm kinda confused about all these things on amps other than the cab

[dohhhhh6]

With all this talk of power amp and junk, my curiosity has finally got the better of me. What exactly is a power amp, a preamp, and a straight head? Or are preamps and heads the same???

 

Could someone please explain in a little detail all the ways to get juice to a cab?

[zeronyne]

A straight head is a combination of preamp and poweramp in one convenient (debatable) package.

 

So a typical combo amp consists of a preamp, a power amp, and speaker(s). Sometimes there are crossovers, compression and effects, but there's always the first three.

 

I'll leave it to real bass players to continue this.

[tim4003]

A preamp shapes/adjust the sound/tone of your bass. A preamp will need to be connected to a power amp.

A power amp powers the signal from the preamp.

A head is a preamp and power amp in one unit.

[g.]

You've been here more than a year and not one of the many times this was answered, and not one of the umpteen zillion contextual clues got across?

 

Omyeffinggod. I am so stooooopid. I typed a lot of those answers and clues. I could have been doing something valuable. Like coming up with more dumb nicks. And copping avatars. Sheesh. What a wasted life.

[rumpelstiltskin.]

the issue would not be so confusing if the following items weren't all generically called "amp":

 

http://www.peavey.com/images/news/wnamm04/BAM-110.jpghttp://www.warwickbass.com/images/quad6sm.gif

 

http://www.crownaudio.com/images/k23q.jpg

 

in the first picture, the new peavey BAM 110, the arrangement is [preamp > power amp > cabinet]. this is most accurately known as a combo amp. you are limited to all three components being from the same manufacturer.

 

in the second picture, the warwick quad VI, the arrangement is [preamp > power amp] + [cab]. the cab is in a separate box from the other components. this is most accurately known as a head, since it sits on top of the cabinet and controls it like a head on a human. you can get cabinets from a different manufacturer than that of the head (and vice versa), so you have some more flexibility. most often, though, people try to match manufacturers out of an artificial sense of balance (and sometimes because they actually just like the sound that much!).

 

in the third picture, the crown K2, the arrangement is [preamp] > [power amp] > [cabinet], where all three components are separate. this type of rig is known as "separates", since all three major components are separate units in their own boxes. very rarely are all three components from the same manufacturer, though it can be done. more often the power amp in this type of setup is a high-power PA amp (like the pictured 2500W crown K2). sometimes the preamp is not bass specific -- the avalon U5 is a popular choice, or any number of parametric EQ units, for example. this type of system lets you get very particular about your sound and manage each component as necessary. though it can often be more convenient and cheaper, because of the great array of products available, this type of rig is rarely both (or either for that matter!).

 

that's probably more verbose than anyone needs. hopefully "verbose" will be confused with "comprehensive".

 

robb.

[NickT]

simple answer..

 

Pre amp makes it sound nice, power amp makes it loud. A head has both sections in one box.

[Hanshananigan]

a guitar or bass, if "passive", has pickups that create a small current. If the instrument is "active" it has a 9v battery inside that boosts the signal, and may allow different eq options using the tone knobs. this set up is essentially one type of "pre-amp".

 

if you plug your bass directly to the amp, the signal from the bass is boosted by the pre-amp so that the signal can be better modified using compression, eq, distortion, etc. that your amp may have. you may have a separate "pre-amp" (volume) knob on your amp that determines the amount of boosting.

 

at this point, the signal does not have the strength to power the speaker. so, the signal is once again boosted by the ("main") amp, which is delivered to the speaker. there will be a volume/main/etc. knob to adjust the amount of boosting, and therefore the overall volume.

 

play with the pre-amp and volume knobs to find a sound that suits you at different levels of loudness. I like to boost the pre-amp as high as possible, but not so high that the sound is distorted. after setting the pre-amp, I then raise the main volume until the desired level of "loudness" is reached.

 

one last thing... an amp's job is basically to take a signal and boost (actually, replicate, I think) it while retaining the same sound qualities it had coming in. an amp for a PA or a home stereo are expected to be "clean". However, the pre-amp, amp, characteristics of the speaker and any effect in between give each amp it's own characteristic "sound."

 

see also:

this page

[Hanshananigan]

oh yeah, and:

 

Combo amp: the pre-amp, (power) amp, and speaker are all in the same unit.

 

http://i11.ebayimg.com/01/i/01/39/a6/0e_1.JPG

 

Head & Cabinet (Together, these can be called a "stack"): The cabinet is the box the speaker(s) is in. the head is the unit that is in a rackmount or sits on top of the "cabinet" that houses the pre-amp and (power) amp. What is referred to as a "power amp" is usually a unit that JUST amplifies a signal to power speakers, without the eq and other effects.

http://img3.musiciansfriend.com/dbase/pics/products/48/482025.jpg

 

I should mention that pre-amps can be found as separate units, alone or part of an effects processor. The stand-alones are used to shape a sound, warm it up, etc. as others have suggested. For example, this unit uses tubes (that aren't great at perfect reproduction, but warm and smooth the sound) and circuitry that has "A unique "deep" control employs a proprietary, tube-driven resonance circuit to provide two levels of boost in the 30Hz region. This circuitry gives unparalleled depth when used with five-string basses and adds superb, sweet thickness to vintage-style instruments." Basically, the unit is built to improve a bass sound.

 

http://img3.musiciansfriend.com/dbase/pics/products/48/487602.jpg