The Source Audio ZIO Analog Bass Preamp + DI is a compact, all-analog preamp pedal for bass with a built-in DI section. It sits on the board between your bass and the rest of your rig, shaping tone with Bass and Treble EQ and a boost, while its balanced XLR direct out sends a low-noise signal to a mixing desk or interface. Source Audio describes it as a "compact and easy-to-dial-in pedal" in a brushed anodized aluminum housing1.
What it does to your sound
The ZIO is built around a clean, transparent preamp rather than coloration. Bass Musician Magazine's reviewer Cláudio Ribeiro summed it up this way2:
"Clean. Clear. Tight. This is a pedal for players who want their bass to sound like their bass, just better."
Delicious Audio describes the ZIO as an all-analog preamp/boost pedal3, so the tone shaping happens in the analog domain with no modeling or presets in the signal path.
Controls and outputs
The front panel keeps things simple: a Bass and Treble EQ section plus an Output control, all footswitchable2.
- TREBLE: boosts or cuts the highs, either to enhance articulation without adding harshness or to smooth attack transients1
- BASS and TREBLE EQ: described by Bass Musician Magazine as "Musical and responsive," thickening the low end and adding top-end sparkle2
- Output: the control the footswitch bypasses along with the EQ2
On the output side, the DIRECT OUT is a balanced XLR with a ground LIFT switch, which Source Audio says delivers a low-noise, yet amp-like signal. A standard 1/4" output lets you run a parallel signal to a pedalboard or bass amp, and there is an extra Tuner/Line output as well13. Ribeiro found the XLR out balanced and noise-free in practice2.
Bypass behavior
The ZIO is True Bypass according to Source Audio1, but the footswitch does not mute everything. Ribeiro's review notes that bypassing "it bypasses the EQ and Output controls, but your DI, headphone out, and signal routing stay active"2. For a player, that means the pedal can keep serving as a DI and practice interface even with the tone shaping switched out.
Headphone output and practice use
A headphone output for direct monitoring is built in1, so the ZIO can double as a silent practice rig: bass in, headphones on, no amp required. Because the headphone out stays active when bypassed2, it keeps working as a monitoring point regardless of the footswitch state.
How it performed with different basses
Ribeiro tried the ZIO with a passive P bass, an active 5-string, and a fretless, and found "the ZIO delivered consistent, polished tone with minimal tweaking" across them2. That makes it a straightforward choice for players who switch between passive and active instruments and want one preamp that behaves the same with both.
Availability
Source Audio's product page currently lists the ZIO Analog Bass Preamp + DI as sold out1.
If you are looking at the ZIO alongside other Source Audio bass gear, the company's bass line also includes the Source Audio Aftershock distortion and the Source Audio Ultrawave Multiband Bass Processor, and the ZIO sits in the broader field of preamp pedals and bass pedals.
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Questions
Does the Source Audio ZIO turn off the DI when you bypass it?
No. Bass Musician Magazine's review found that the footswitch bypasses the EQ and Output controls, but the DI, headphone out, and signal routing stay active. Source Audio also lists the pedal as True Bypass, so the core signal path is preserved when the tone-shaping section is switched out.
Does the ZIO Bass Preamp + DI have a headphone output?
Yes. Source Audio lists a headphone output for direct monitoring, which lets you practice or check your tone without an amp. The review in Bass Musician Magazine noted that the headphone out stays active even when the pedal is bypassed.
Does the ZIO have a balanced XLR output?
Yes. The DIRECT OUT is a balanced XLR output with a ground LIFT switch, which Source Audio describes as delivering a low-noise, amp-like signal to a mixing desk or interface. Bass Musician Magazine's reviewer called the XLR out balanced and noise-free.
What do the Bass and Treble controls on the ZIO do?
The TREBLE knob boosts or cuts the highs, either to enhance articulation without adding harshness or to smooth attack transients. Bass Musician Magazine described the Bass and Treble EQ as musical and responsive, thickening the low end and adding top-end sparkle.
Is the Source Audio ZIO still available?
Source Audio's product page currently lists the ZIO Analog Bass Preamp + DI as sold out, so it is not available directly from the maker at the moment.
Does the ZIO work with both passive and active basses?
Bass Musician Magazine's reviewer tried the ZIO with a passive P bass, an active 5-string, and a fretless, and found it delivered consistent, polished tone with minimal tweaking across all of them.
Sources (3)
- ZIO Analog Bass Preamp + DI, Source Audio
- Gear Review: Source Audio ZIO Bass Preamp + DI, Bass Musician Magazine, 2025-05-19
- Source Audio ZIO Analog Preamp/Boost, Delicious Audio, 2024-01-09
