The Sushi Box FX Neptunium is a tube preamp pedal with a D.I. output, made for going straight to front of house or a recording interface. It runs a 12AU7 tube, powered by a standard 9-12VDC supply that the pedal steps up internally to over 300V, and it adds a switchable high-pass filter to keep lows out of the way in a mix1.
The Neptunium was a limited run pedal and is now listed as Archived by Sushi Box FX, so it is no longer in current production12.
Where it came from
As its name implies, the Neptunium is based on the Nobelium preamp, which is in turn based on a high-end studio tube preamp1. It sits in Sushi Box FX's range of tube preamp pedals alongside models like the Underground Accelerator2.
Controls and outputs
| Control | What it does |
|---|---|
| Face volume control | Affects the 1/4″ output1 |
| Two-band tonestack | Based on the classic Fender/Marshall/Vox tonestack; both controls are boost-only, with a flat response with both controls all the way off1 |
| High-pass filter switch | Rolls off lows at -6dB per octave below 90Hz to prevent muddiness in a mix1 |
| Side XLR volume control | Separate volume control affecting the XLR output, on the side of the pedal next to the XLR jack above the ground lift switch1 |
The split output arrangement means the 1/4″ output and the XLR D.I. output are set independently: the maker notes that rather than make the XLR output a fixed level, a separate volume control affecting the XLR output was added to the side of the pedal1.
Power
The Neptunium takes a standard 9-12VDC center-negative power supply and steps up the voltage internally to run the 12AU7 tube at over 300V1. Sushi Box FX recommends a supply capable of delivering at least 400mA; using less than this can damage the power supply and/or the pedal1. The maker offered the option to include a power supply with the pedal1.
Because of the 400mA current requirement, the Neptunium needs its own dedicated supply output; a standard low-current pedalboard outlet will not run it1.
Videos
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Questions
What tube does the Sushi Box FX Neptunium use?
The Neptunium uses a 12AU7 tube. It takes a standard 9-12VDC center-negative power supply and steps the voltage up internally to run that tube at over 300V, which is how a pedal-sized enclosure can house a genuine tube circuit.
Does the Neptunium have an XLR output?
Yes. Alongside the 1/4″ output it has an XLR D.I. output with a ground lift switch, intended for going straight to front of house or a recording interface. The face volume control affects the 1/4″ output only, and a separate volume control on the side of the pedal, next to the XLR jack above the ground lift switch, sets the XLR level.
How much current does the Neptunium need?
Sushi Box FX recommends a 9-12VDC power supply capable of delivering at least 400mA. Using less than that can damage the power supply and/or the pedal, so a standard low-current outlet is not enough.
What does the high-pass filter on the Neptunium do?
It is a switchable filter that rolls off the lows at a rate of -6dB per octave below 90Hz, which the maker describes as a way to prevent muddiness in a mix.
Is the Sushi Box FX Neptunium still made?
No. The Neptunium was a limited run pedal, and it now appears as Archived on the Sushi Box FX product pages, so it is no longer in current production.
Sources (2)
- Neptunium, Sushi Box FX
- Underground Accelerator, Sushi Box FX
