From Source Audio:
The goal in creating the ZIO Analog Front End + Boost was simple yet ambitious: “Make Everything Sound Better!” ZIO is an all-analog preamp/boost pedal that includes a choice of four distinct preamp circuits, each with up to +20dB of additional output boost. ZIO is Source Audio’s first all-analog effects pedal and designed in collaboration with Christopher Venter, the owner and sole engineer at SHOE Pedals.
ZIO is a deceptively flexible unit that can serve many different purposes at various places in your signal path. Use it at the front of your chain of effects to shape the rest of your outgoing tone, after your drive pedals as an overall tone sweetener or clean volume boost, or at the the end of your pedalboard to drive a long cable run or as a restorative device to recreate the sound of your guitar going directly into the input of your amplifier. You can also use the ZIO in your amp's effects loop if you want to drive your power amp even harder, or to compensate for a level mismatch between two channels.
The word "ZIO" is an acronym for Impedance (“Z” is the electrical symbol for impedance), Input (“I”), and Output (“O”). The pedal is designed to take a guitar’s high impedance signal, sweeten the tone with any of its four preamp circuits, and output a strong, low impedance signal that won’t be altered by the buffered dry tones of effect pedals further down the signal chain. High fidelity, noise-free Burr-Brown op amps help give ZIO extreme clarity and responsive pick dynamics, while maintaining ideal body and warmth. ZIO has four distinct preamp circuits. JFET offers a completely transparent signal boost with zero coloring or distortion. LOW-CUT reduces “tubby” bottom-end for a tighter sound with added headroom. STUDIO finds inspiration from the time-honored “Pultec Trick,” a studio technique that adds clarity by cutting the “mud frequencies” and adding mid-range articulation. E-PLEX captures the focused and subtle grit of the preamps found in vintage Echoplex Tape Delay units. The ZIO’s TONE toggle offers three different levels of capacitance (or simulated cable length) to brighten or darken the tone.