The Sadowsky Outboard Bass Preamp/DI is a bass preamp and direct box built into a pedal, made by Sadowsky. Guitar FX Layouts describes it as containing "the same famous circuitry built into every Sadowsky bass," so a player with a passive or vintage bass can put the Sadowsky onboard tone stack in front of any amp. It can feed an amp and go direct to the board at the same time: plug the bass into the box, then run from the box to the amp, and/or direct to the PA1.
Roger Sadowsky first unveiled an Outboard Bass Preamp in 1990, and it was welcomed by passive and vintage bass owners as an alternative to modifying their instruments. The original attached to a strap or belt with the volume, bass, and treble knobs pointing up and out. The updated floor version reviewed by BassPlayer in April 2002 added a bypass and mute footswitch, a tuner out, an AC adapter jack, an XLR out with a ground-lift switch, a low-battery indicator, and an easy-access battery compartment, changes Sadowsky made based on customer feedback2.
The controls: volume, treble boost and bass boost
The controls consist of volume, treble boost and bass boost1. Both tone controls are fixed-frequency boosts, so the knobs set how much lift rather than which frequency:
| Control | What it does |
|---|---|
| Volume | Sets overall output level1 |
| Treble boost | +13 dB boost at 4 kHz1 |
| Bass boost | +13 dB boost at 40 Hz1 |
That is the whole face of the unit: a volume knob and two boost knobs, one for treble and one for bass, which is why it works as a set-and-forget tone shaper rather than a full EQ. For other preamp designs with more sweeping control, see the Preamp Pedals type page1.
Outputs and signal flow
The updated version gives a player several ways out of the box2:
- Balanced XLR out with a ground-lift switch, for going direct to the board
- Tuner out, for silent tuning
- 1/4-inch output to an amp
- AC adapter jack
- Bypass and mute footswitches
The ground-lift switch on the XLR matters in club situations, where a loop between amp and PA can put hum on the direct feed. The mute footswitch also makes it practical as a DI on a gig: a player can kill the signal between songs without touching the amp2.
The original 1990 unit attached to a strap or belt and had XLR outs but no footswitches. The bypass and mute footswitches, tuner out, AC adapter jack, and ground-lift switch belong to the updated floor version2.
Specifications
Guitar FX Layouts lists these figures for the pedal1:
| Specification | Value |
|---|---|
| Input impedance | 330K ohms |
| Output impedance, XLR | 600K ohms |
| Output impedance, tuner out | 1K |
| Output impedance, 1/4-inch out | 10K |
| Frequency response | 5 Hz to 50 kHz |
| Total harmonic distortion | 0.1% at 1 kHz |
The wide frequency response and low distortion figure reflect its role as a clean preamp: it shapes tone with boosts rather than adding grit of its own1.
What reviewers and players found
BassPlayer's April 2002 review by E.E. Bradman put the unit to work on real stages: "In a 12-piece R&B band, one staffer used the Sadowsky as a tone-shaping DI," across a small jazz club, a medium-size bar, and a 5,000-square-foot venue2. Reliability also came up in the same review. Roger Sadowsky said of the units sold to that point:
"Out of the 700 units I have sold, only three were defective, and none of those involved the pots or battery compartment."
The DIY community has kept the circuit alive too: Geiri published a stripboard layout of the Sadowsky preamp on Guitar FX Layouts in April 2013, with builder verification and wiring corrections following in the comments1.
Where it sits in the Sadowsky line
The Outboard Bass Preamp/DI is the ancestor of Sadowsky's later preamp pedals. In May 2017, Bass Musician Magazine reviewed the Sadowsky SBP 1 and SBP 2 preamp/DI pedals, with Roger Sadowsky explaining the FET circuit and preamp history. In March 2020, Sadowsky launched the SPB-1 and SPB-2 bass preamp pedals, bringing its instrument preamp electronics into pedal form. Players looking at the current line can read about the Sadowsky SBP-1, the Sadowsky SPB-1, and the Sadowsky SPB-2, or browse Bass Pedals more broadly.
Videos
Mika Salovaara
Questions
How long does the battery last in the Sadowsky preamp pedal?
Guitar FX Layouts lists battery life at 90 hours on one 9-volt battery, with an AC adapter as the alternative power source. The updated version also adds a low-battery indicator and an easy-access battery compartment, so a dying battery is not a surprise mid-set.
Does the Sadowsky preamp pedal have an XLR output?
Yes. The original version had XLR outs, and the updated version reviewed by BassPlayer in 2002 includes a balanced XLR out with a ground-lift switch, alongside a tuner out and a 1/4-inch output. That lets the pedal feed the PA directly while still driving an amp.
Is the Sadowsky Outboard Bass Preamp/DI made in the USA?
Yes. BassPlayer's 2002 review lists the unit as made in the U.S.A., with a one-year parts and labor warranty.
Does the Sadowsky preamp pedal have a ground-lift switch?
Yes. The updated version has an XLR out with a ground-lift switch, which helps when a ground loop between the amp and the PA causes hum through the balanced output.
What is the input impedance of the Sadowsky Outboard Bass Preamp/DI?
Guitar FX Layouts lists the input impedance at 330K ohms. Output impedance varies by output: 600K ohms at the XLR, 1K at the tuner out, and 10K at the 1/4-inch output.
Sources (2)
- Guitar FX Layouts: Sadowsky Preamp, Guitar FX Layouts (tagboardeffects.blogspot.com), 2013-04-23
- BassPlayer_2002APR.ill, BassPlayer, 2002-04
