While the Harmonic Booster by Darkglass Electronics is a superb 'standard' preamp, it's actually built to form a perfect tone-shaping duo alongside one of the brand's range of distortion pedals.
With the Vintage Ultra V2 bass overdrive/preamp, Darkglass had already created the holy grail. With the Vintage Ultra V2 AUX, they push things even further.
The Microtubes X7 builds on the firm legacy of the Darkglass Microtubes X. The X7 is the Swiss army knife of bass preamp/distortions, made to swiftly and brutally open a bass-flavoured can of worms.
With the Alpha-Omega Ultra V2, Darkglass Electronics release a bass distortion effect pedal with the same level of versatility as a Swiss Army knife!
The AG Preamp by Aguilar gets you an analogue bass preamp and DI in one compact pedal that lays various tasty sounds based on popular AG amps at your feet, and with more than enough headroom.
As a bi-amp preamp pedal, The Bass Butler from Orange serves bassists more mid-range presence alongside the other instruments in the mix while fully maintaining all of the lows.
The Stadium DI Box was originally developed by the bass players at LR Baggs for their own personal use. It offers studio quality and is made of top-notch components.