The Master Effects JC-Pre is a preamp pedal based on the clean channel of the Roland JC-120 Jazz Chorus amplifier, the amp the maker describes as a classic whose sound "has been heard on count"less records. It puts that clean solid-state voicing on a pedalboard, with a 3-band EQ and Volume control, plus Bright and Gain toggles for tailoring it to the guitar plugged into it1.
Controls
| Control | What it does |
|---|---|
| 3-band EQ | Tone shaping across three bands1 |
| Volume | Output level1 |
| Bright toggle | Can cut some of the highs to help tame overly bright guitars1 |
| Gain toggle switch | Prevents guitars with high output pickups from clipping the input stage1 |
The Bright toggle works in the opposite direction from the bright switch found on many amps: rather than adding treble, it trims it, which is useful when a guitar with a sharp-sounding pickup set makes the clean channel sound thin or spiky. The Gain toggle serves a similar housekeeping role at the other end of the signal, padding down hot pickups so they do not clip the input stage and muddy the clean tone1.
Power and headroom
The pedal runs from a standard boss-style 9V power supply, the same center-negative supply most pedalboards already carry. Inside, the circuitry generates approximately 30V, which Master Effects says gives "enormous amounts of headroom, just like the original ampli[fier]". Headroom matters here because the whole point of the pedal is staying clean: more internal voltage means the preamp can handle hot signals before it starts to break up1.
The JC-Pre uses a 9V boss-style supply. Master Effects' warranty excludes damage from an improper power supply, so the pedal should be powered as specified1.
Price, availability and warranty
The JC-Pre is priced at $199US plus shipping, as of the maker's product page dated 26 October 2026. Shipping within Canada and the US is $20US, and shipping to the UK, Western Europe, Australia, and Japan is approximately $60US1.
Each pedal is built on a professionally assembled PCB and proudly assembled by hand in Calgary, Alberta, Canada. It carries a 1 year warranty on parts and labor, excluding damage from improper power supply or misuse1.
Where it sits on a board
As a preamp, the JC-Pre is designed to stand in for an amp's front end rather than add an effect on top of a sound, so it typically goes where an overdrive or boost would, ahead of time-based effects. Players building a clean-platform rig around other Master Effects pedals, such as the Transmission, Seventh Son or Super Forty, can pair it with delay and chorus pedals in the manner of the original amp's stereo effects setup. For more on the category, see Preamp Pedals1.
One piece of Jazz Chorus history worth knowing: in an interview for BOSS, Doug MacArthur explained that Steve Vai's original Jazz Chorus "didn't have an effect loop. We needed the loop to control the master volume using a foot pedal", which is why a loop was added to later versions2. The JC-Pre itself is a preamp pedal and the maker's page does not describe an effects loop on it.
Videos
Eric Merrow
Master Effects Pedals
Questions
What amp is the Master Effects JC-Pre based on?
The JC-Pre is based on the clean channel of the Roland JC-120 Jazz Chorus amplifier, the stereo solid-state amp that Master Effects describes as a classic. The pedal aims to put that clean preamp voicing on a pedalboard, with a 3-band EQ and Volume control matching the amp's channel layout.
What power supply does the Master Effects JC-Pre use?
The JC-Pre runs on a standard boss-style 9V power supply. Internally, the pedal's circuitry generates approximately 30V, which Master Effects says gives it enormous amounts of headroom, just like the original amplifier.
What does the Gain switch do on the JC-Pre?
The Gain toggle switch prevents guitars with high output pickups from clipping the pedal's input stage. It is there to keep the clean channel clean when a hotter guitar is plugged in, alongside the Bright toggle and the 3-band EQ.
What does the Bright toggle do on the JC-Pre?
The Bright toggle can cut some of the highs to help tame overly bright guitars. It works the other way round from a typical bright switch: instead of adding sparkle, it trims treble when a guitar sounds too sharp through the pedal.
Where is the Master Effects JC-Pre made?
Master Effects assembles the JC-Pre by hand in Calgary, Alberta, Canada, on a professionally assembled PCB.
What warranty does the Master Effects JC-Pre have?
Each JC-Pre comes with a 1 year warranty on parts and labour. The warranty excludes damage from an improper power supply or misuse.
Sources (2)
- JC-Pre | Roland Jazz Chorus Clean | Preamp Pedal | Master Effects, Master Effects
- Behind the Board: Doug MacArthur with Steve Vai, BOSS (articles.boss.info), 2025-01-30
