The Korg OD-S BK, sold as the Nutube Overdrive BK, is an overdrive pedal built around the Nutube, a miniature vacuum tube Korg developed itself. Korg says the pedal delivers "リアルな真空管サウンドを楽しめます" (real vacuum tube sound you can enjoy), and because the Nutube draws so little power, the pedal can run on batteries1.
The OD-S BK is a variant of the Korg OD-S. The OD-S series was originally sold as a build-it-yourself kit, and the BK model is the factory-assembled version: Korg describes it as the "組立不要モデル" (assembly-free model) that arrives complete out of the box1. Players who want the building experience can look at the kit version, the Korg Nu:Tekt OD-S.
Controls
The pedal keeps its control set small and focused on the tube itself. Korg lists two knobs2:
| Control | What it does |
|---|---|
| GAIN | Adjusts the input level going into the vacuum tube2 |
| TUBE GAIN | Changes the distortion by altering the load on the anode of the tube circuit2 |
There is also a switch that changes the circuit between a single and a double Nutube configuration, and the pedal includes true bypass, so the effect is removed from the signal path entirely when off2.
Where it sits in the Nutube range
Korg introduced Nutube technology in 2015, and the tube has since appeared in a range of drive pedals, including the Korg Nu:Tekt OD-S kit, the Korg HG-S High Gain OD and the Korg TR-S Power Tube Reactor. For a broader look at how this kind of pedal shapes a signal, see the site's page on overdrive pedals.
Questions
What is the difference between the Korg OD-S BK and the OD-S kit?
The OD-S series originally shipped as a build-it-yourself kit that the player assembled without soldering. The BK model is the same Nutube overdrive circuit but arrives fully assembled from the factory, so it needs no building. Korg describes it as the assembly-free model of the OD-S series.
What does the Nutube do in the OD-S BK?
The Nutube is a miniature vacuum tube developed by Korg. In the OD-S BK it sits in the overdrive circuit, and Korg says the pedal delivers real vacuum tube sound while still being able to run on batteries. A switch lets you change between a single and a double Nutube configuration.
