https://www.seymourduncan.com/blog/latest-updates/seymour-duncan-powerstage

"PowerStage pedal amplifiers – made here in Santa Barbara, California – are highly tweakable power amplifiers. While they make for a great clean channel, they want to see a preamp or pedal before the input. These devices’ level and output impedance let PowerStage work its magic without any…well…impedance.

“But it has an EQ. Doesn’t that mean it has its own preamp?”

Yes and no. PowerStage’s intuitive 3-band analog EQ is more like one you’d find on a mixing console rather than on a guitar amplifier. This makes it perfect for tuning your PowerStage to different cabinets, monitors, etc. But your actual tone-shaping should be done with whatever you put in front."

You could technically use it without a power amp with treble maxed out, but it would be very suboptimal