why would you need a pre amp for speakers/headphones

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I understand the point of an amp is to boost the power going to the equipment but everytime I look up what preamps do I just get confused on why they are nessecary and how they affect it differently than an amp. Is it just a separate signal booster in the chain? When would you need one? Why wouldn’t a stronger amp do the same thing or have it built in already?

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“A preamplifier, also known as a preamp, is an electronic amplifier that converts a weak electrical signal into an output signal strong enough to be noise-tolerant and strong enough for further processing, or for sending to a power amplifier and a loudspeaker. Without this, the final signal would be noisy or distorted.”

“The point is, while they both apply a gain boost to the signal, they do it for different reasons. Primarily the preamp is there to create a line level signal, but it can also add gain creatively to alter the base sound that the power amp will have to work with. Preamps can also generate distortion.”-[source](https://higherhz.com/preamp-vs-power-amp-difference/)

What this means to me is the pre-amp is one of the first things to effect the sound. It brings lower sounds, such as bass, to “line level” (comparable volume to the rest of the sounds) while a regular amplifier is one of the last things in sound line that amplifies the entirety of the line level.

TLDR- pre amp brings lower sounds to line level with the rest of the sounds

Power amp amplifies all the sounds in general.

Without preamping lower sounds can come out distorted or the whole thing just won’t sound entirely right.

The output from some devices like microphones or electric guitars or whatever is pathetically weak. Like, the signal that comes out of a guitar’s pickup is really not powerful at all. Stronger than noise, but not by a whole lot. The pre-amp boosts the signal so that it actually is significantly stronger than the noise. That makes it easier and less complicated to process that signal down the chain, since the separation between signal and noise is now much clearer.

If you are using DAC that can do the standard 2Vrms via RCA (or better: 4Vrms via balanced XLR), then you can use most power amps without a preamp. But some do require more voltage, some even 11Vrms or higher; many are rated at only needing ~1.2Vrms though.

A preamp can have many functions though. It can be active and boost the incoming signals to be powerful enough for the amp. It can simply be a source switcher. It can be passive and only for volume control.

Speakers with more turns on their coils can produce sounds with lower noise and/or distortion. The problem is that more turns increases the impedance of the speaker which requires more power to drive at the same amplitude.

Your normal headphone outputs are designed to drive headphones with impedance of less than 50 ohms. Higher quality headphones will have a higher impedance–up to 600 ohms. Your headphone output just won’t have the power to drive that impedance–especially not to a high level. A pre-amp can boost the power, and have an output impedance closer to the headphone’s impedance (maximum power is delivered when the impedances match).

I have a headset with an 80 ohm impedance. While the headphone jack on my computer will drive it, it won’t get very loud even at max volume.