Source Audio ZIO Analog Preamp/Boost

The Source Audio ZIO Analog Front End + Boost is an all-analog preamp and boost pedal with a choice of four preamp circuits and up to +20dB of clean signal boost¹. Announced in January 2022, it was the company's first all-analog effects pedal, designed in collaboration with Christopher Venter, the owner and sole engineer at SHOE Pedals². It is built around high-fidelity, noise-free Burr-Brown op amps, which Source Audio credits with the pedal's clarity and responsive pick dynamics¹.

The idea behind the pedal is signal conditioning: it takes a guitar's high impedance signal, sweetens it with one of the four preamp circuits, and outputs a strong low impedance signal that is unaffected by the buffered dry tones of other pedals further down the chain³. Gearnews described it as working almost like a buffer, preamp and booster all in one².

A transparent preamp, buffer and boost

Source Audio designed the ZIO, in its own words, to "make everything sound better"⁴. In practice it does three jobs at once. As a boost pedal, the Output control delivers up to +20dB of signal boost¹. As a buffer, it converts the guitar's high impedance signal into a strong low impedance one that holds up over long cable runs and through other pedals³. And as a preamp, each of its four circuits adds its own character, from fully transparent to gently voiced¹.

Guitar World's reviewer, Trevor Curwen, noted that the pedal "acts as a buffer and has a Tone switch that offers three different levels of capacitance"⁴. The JFET circuit is the cleanest of the four: in Curwen's testing, it "will retain your core tone but make it louder and more robust," with unity gain sitting at about the 10 o'clock position on the Output knob⁴.

The pedal is compact, at 4.1 inches long by 2.36 inches wide by 2.22 inches high including the knobs, in a brushed anodized aluminum housing³. It is made in China⁴.

Four preamp circuits: JFET, Low-Cut, Studio, E-Plex

The Circuit switch selects one of four discrete preamp circuits, each with up to +20dB of boost available¹².

The JFET mode is the reference point: Source Audio describes it as "a completely transparent signal boost with zero coloring or distortion," with a character and behavior similar to a clean tube amp input¹. Low-Cut trims the low end, which Source Audio says gives a tighter sound with more headroom, useful with gain-heavy overdrive and distortion pedals or dark amplifiers¹.

The Studio circuit is the most studio-flavored of the four. It is built on the "Pultec Trick," an EQ approach used on records since the 1950s and still in use today¹. Guitar World's reviewer called it "a real tone-sweetener that combines a mild lower-mid" scoop with a higher boost for clarity and articulation⁴. The E-Plex circuit, meanwhile, reaches for the preamp stage of the vintage Echoplex tape delay, a unit long prized by players as a front-end boost; Source Audio says it captures that preamp's focused and subtle grit¹.

Guitar World's review summed up the four-circuit approach as a plus, listing "four preamp options" among the pedal's strengths⁴.

Power and connections

The ZIO runs on 9V DC, center negative, drawing about 20mA, so it fits a standard pedalboard power supply³. Connections are a standard input and standard outputs, plus an extra Tuner/Line output for feeding a tuner or a second line destination without tapping the main signal¹⁴³.

The bass version: ZIO Analog Bass Preamp + DI

Bass players get their own variant. The ZIO Analog Bass Preamp + DI is a compact, easy-to-dial-in pedal that Source Audio says works equally well in front of an amplifier or as a preamp and direct box via its balanced XLR output⁵. Like the guitar version, it is all-analog with true bypass and the same brushed anodized aluminum housing⁵.

Its Output knob offers up to +16dB of overall boost above unity gain, or up to -6dB of cut⁵. It also carries a SCOOP toggle that engages an EQ curve based on the same Pultec trick as the guitar pedal's Studio mode: a low-mid cut to remove mud frequencies, a gentle presence boost in the upper midrange, and a natural-sounding high pass filter⁵. More bass pedals are covered separately on the site.

Where it came from

The ZIO Analog Front End + Boost was designed in collaboration with Christopher Venter, the owner and sole engineer at SHOE Pedals³. Delicious Audio's 2024 coverage described it as Source Audio's first all-analog effects pedal, built with high-quality components and Burr-Brown JFET op-amps, in a catalog otherwise known for digital designs³. The same coverage noted that the pedal takes a guitar's high impedance signal and outputs a strong low impedance signal unaffected by buffered dry tones of other pedals³.

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