different preamp devices do different things .  basically it takes your smaller input signal like a Mic or a guitar or the out on your tuner and amplifies and allows you to shape the sound and make the output signal more bigger.  stomp boxes boost the signal to the input of a combo amp but the pre amp in the combo amp also amplifies and shapes the signal bigger so the power amp has the right size signal and impedance to drive the speakers ultimately...  some are designed for mics or turntables or pianos or guitar pickups all have different stages and levels of audio signal they are designed for... if u break it down

pre - before
amplifier - device that magnifies sound or signal

it's a amp that is for driving your next amp up to the power amp which drives the speaker or load.

I wanted to answer the question in my own words but if I have any misinformation here i will be happy to fix it.

I found this preamp in a donation pile along with a 8 channel DAW A 4 channel mixer and a old hi fi 12 band eq and effects rack mount processor.  I love how you can dial in a good range of frequencies to center the bass mids and treble around but looking at the guts and the schematic there is so much discrete stuff going on in there the parts numbers are im the 2000s and I'm intimidated and also don't want to butcher the preamp it's pretty nostalgic and works perfect still. rather than a bunch of eq sliders I'd be happy with knobs and possibly a variable q for each band but I'm looking for some suggestions.  I could keep it separate and try just a pedal format but a robust tone section would bolster my enthusiasm if i could successfully incorporate this into a solid state preamp driving a lm3886 power section for guitar and bass could share the same tone section if I could achieve this.  am looking forward to your comments suggestions stories all is welcome.  I'm not a novice nor a pro but I know what i want and im good with my hands and brain.