What's the purpose of a preamp?

What are the advantages? Does it have more detail for lower passages? It couldn't be loudness heck I can shake the walls with my Luxman 450!

 

Your Luxman has a preamp already inside, you Knucklehead.

 

To preamplify.

 

So what the heck is a preamp?

 

On your receiver Larry, it's all the functions of the dials/buttons/knobs. A pre-amp is just a seperate version of this with no built-in tuner or amp section, hence a seperate. In turn your amp and tuner would also be seperates.

It's purpose is to receive an audio signal from a source like your CD player, tuner, or turn table (providing you have a built-in phono stage that is as opposed to only a line-level pre amp where then you require a seperate phono pre amp) and send it to the amplifier.

 

A preamplifier is just an amplifier that has enough output to drive another amplifier. Usually they are used for microphones, phono cartridges, and tape heads which need a fair amount of gain to drive a power amp. They also can be used with line level inputs where gain is not needed. They often have eq facilities as well. The phono and tape head inputs will have usually have RIAA, or NAB equalization which are required to compensate for the non linear curves of the cartridge or tape head. They usually have a volume control and often have tone controls.

Some people will run a cd player or other line level source directly into an amplifier, but using a preamp allows more control, and often drives the amplifier better.

Sometimes preamplifiers are used as buffers or to provide extra gain before another preamplifier, such as with a low level phono cartridge.

A receiver usually has a preamplifier, tuner, and power amplifier all in one unit.

 

I had a post on this a while back and now I cannot find it now. Any integrated stereo amp usually has three sections to it (a receiver is an integrated amp with tuner so it has four sections). The first section is the phono amp ( sometimes omitted in modern equipment), this section is a very high fixed gain amplifier. It is meant to take the very low voltage signals from the TT cartridge and amplify them by a 1000 times or more (less than a mv to about 2 volts). The next section is the pre amp, it is usually the only variable gain section in the integrate amp or receiver (it has a volume control). It can take signals that are about 1 to 2 volts and either attenuate them (low volume) or boast them by a factor of as much as 5 or so depending on the amp. The pre amp also acts as the switching unit between multiple sources (tuner, cd, tape, TT, aux, etc.). Finally there is the power amp section, this where the signal gets its final boast to voltage and current levels that will drive your loudspeakers. This is also a fixed gain section. Volts x Amps = Watts and that is the unit that integrate amps, separate power amps and receivers are museared by. Things vary greatly in this section from a few watts for single-ended-triode (SET) amps to behemoths that producer over a 1000 watts (usually solid state, but there are few tube amps that can go to these power levels). How much power you need depends on the efficiency of your speaker, the size of you listening room and how load you like your music. Hope this helps.

 

This is correct when it comes to preamplifiers.