Can someone explain to me power amps and pre amps?

[BrianH]

I admitedly don't know much about equipment... but would like to know what the purpose of power amp and pre amps are? Maybe dumb question, but well if you don't know you don't know!

[darren wilson]

Think of it this way: The preamp controls the gain... the amount of distortion in your sound. The power amp controls the overall master volume of your sound.

[Two hands31]

The way I understand it is, the pre-amp shapes your sound, the power amp makes it loud (it also shapes the sound a bit, depending on the company, model, etc).

[BrianH]

Actually I'm more wanting to know what the add on power amps and pre amps(if I'm referring to them correctly) are for? You know like the Mesa 50/50 and new rectifier recording pre-amp?

I don't understand why you need them or what their purpose is?

[gkelm]

It's not a matter of an add-on, but rather using separate components (preamp + power amp) vs. a combined unit like a combo or head. All guitar amps have both a pre- and power amp...rack systems generally use separates. One advantage to a rack rig is stereo capability (also midi preamp/effects switching, etc).
Greg

[texshred777]

Originally Posted by gkelm

... One advantage to a rack rig is stereo capability (also midi preamp/effects switching, etc).
Greg

AND, you can get some mix 'n match action going... Boogieish preamp into el34 equipped power amp, or marshallesque pre into a 6l6 equipped power amp.

[bduersch]

And even better, with the proper switching system you can do both at once... Marshall and Mesa preamps into a common power amp! Use only the Marshall, use only the Mesa, use the Marshall left and the Mesa right... tons of options!

--B

[mike777]

TwoHands31 pretty much summed it up. A preamp is exactly how it sounds: pre(before) the amplifier. The amplifier is actually the element in the that delivers the power to the speaker. We just often loosely refer to the whole shebang as an amp whether we are talking combos or stacks.

A separate power amp is a module that is used for control of the amp section only to power the speakers. It wouldn't have the preamp section built into it. You would by a separate preamp for that. If you are still using rack-mounted equipment or are considering that, this will most likely be the route you would go. It's bulky but if you like the preamp abilities from one brand and the power delivered by another, you could mix and match. Some pre-amps are programmable which could come in very handy if you change your sounds frequently.

Mike 777 Haug

[BrianH]

so if you use amps that have everything built in, then there is no need or use for this equipment or could there be a nice way of using this equipment to add to or alter your tone through your current amp?

thanks for all the great info guys...

[bduersch]

Well, if you really like the tone (preamp) of your current amp but don't have enough power, you could connect the FX send from your amp to a separate power amp and have more power!

Or, if you don't like the tone of you current amp but like it's power section, you could connect a separate preamp into the FX return on your amp. Generally, using two preamps at a time doesn't sound too great--using the FX send/return allows you to bypass the preamp in a combo.

But in most cases, you don't get a lot of benefit out of using different preamps/power amps with an existing amp... it might be a sign that it's time to get a new amp!

--B

[gkelm]

Just an additional note...before I got into experimenting with different rack power amps, I had no idea how much difference the power amp made in tone. Quite often this is underestimated. While it's not as dramatic a change as a different preamp, power amp tone in nonetheless significant. (IMHO, especially when you consider tube vs. SS).
Greg

[7 Dying Trees]

Preamp: Takes your weedy low power guitar signal and turns it into a very large voltage signal. Preamps are important, as is high gain at this stage to make sure that any noise that gets into the system is not too noticable. Also shapes the sound a lot. The pre amp is essentially the circuit that gives your amp that fenderish/boogie/marshall sound. Also takes care of distortion and the like.

Power amp: Speakers don't like large voltage signals. In fact speaker work on large current signals. What the power amp does (in simple terms) is convert the large voltage signal (which has little current to it) into a large current signal that will make the speakers move back and forth so you can produce sound. In effect you are taking the signal and adding power to it, ie, volume to bring it up to an audible (and preferably ear shattering) level

Why have them seperate? Well, the best place to really put most effects and things which will add noise (all effects add noise) is after the preamp, so that the effect comes out, but not the noise it produces (this is why you have an FX loop).

Also, just like with reamps, there are differences in power amps. Some will have a looser feel to them, some will be very tight and focused. The best thing about racks is that you can mix and match untill you find something that's nice tyo your ears and gives you the sound you want.

:P

[texshred777]

AND, once you get a huge, and quite cumbersome rack like jeremy's...then you can make your friends feel special as 'guitar tech' for a day and haul it around for you. Of course, that's usually a one time thing, unless your friends are really cool or getting paid well.