The Sushi Box FX JC Emerald is a tube preamp pedal based on the preamp of one of the best known British tube amps of the 1980s. The maker says the circuit has been modified to make it more suitable for pedal and preamp use while staying true to the original tone, and the latest version adds toggle switches to make the preamp design more flexible1. It sits in the wider family of preamp pedals from Sushi Box FX, alongside designs like the Underground Accelerator and Venus Z.
The JC Emerald's product page is marked Archived on the Sushi Box FX site, so the pedal is no longer presented there as an active product.
Controls and voicing
The JC Emerald's voicing switches change how the amp preamp responds:
| Switch position | What it does |
|---|---|
| Brite switch on | Stock preamp1 |
| Deep switch on | Low-end boost1 |
| Both switches off | Treble rolled off1 |
| Both switches on | Extra low end with a sparkly grind up top1 |
For bass players chasing a particular classic tone, the maker suggests trying both switches on: "If you're looking for that Lemmy-esque bass tone, try turning both switches on for some extra low end but some nice sparkle up top"1.
The Summer 2024 revised edition
The Summer 2024 revised edition keeps the same circuit as before but adds upgrades, including film capacitors in the audio path and soft-touch relay bypass switching1. Sushi Box FX applied the same approach to other pedals in its range around that time, with revised editions of the Underground Accelerator and Elementary adding film capacitors and relay bypass while keeping their original circuits.
Power
Because the JC Emerald is a tube pedal, it draws more current than a typical compact pedal. The maker recommends a 9 to 12V DC power supply capable of delivering at least 600mA1. A supply rated for that draw matters here: a standard low-current outlet or daisy chain may not run a tube pedal correctly.
Videos
BASSED.
Questions
Is the Sushi Box FX JC Emerald a tube pedal?
Yes. Sushi Box FX describes the JC Emerald as a tube pedal, and the maker notes that as a tube pedal it requires a high amount of current to operate correctly. The recommended supply is 9 to 12V DC capable of delivering at least 600mA, which is more than many standard pedal power supplies provide.
What does the Deep switch do on the JC Emerald?
The Deep switch adds a low-end boost when switched on. With both the Brite and Deep switches off, the treble is rolled off. With both switches on, the maker describes a bass tone with extra low end and a sparkly grind up top.
Does the JC Emerald use true bypass?
The Summer 2024 revised edition of the JC Emerald uses soft-touch relay bypass switching. The maker says the revised edition keeps the same circuit as before but adds upgrades including film capacitors in the audio path.
What power supply does the JC Emerald need?
Sushi Box FX recommends a 9 to 12V DC power supply capable of delivering at least 600mA. Because the pedal is a tube design with a high current requirement, a supply rated for that draw is needed.
Is the JC Emerald still in production?
The JC Emerald's product page is listed as Archived on the Sushi Box FX site as of October 2026, so the pedal is no longer presented as an active product there.
Sources (1)
- JC Emerald, Sushi Box FX
