The Electro-Harmonix Cntl Knob is a static expression pedal: instead of rocking a pedal back and forth, it stores two preset expression values and toggles between them with a single footswitch. Electro-Harmonix describes it as letting you "set two preset values that represent two positions of a traditional expression pedal and toggle between them"1. It is a expression remote control for any device with an expression control jack, built as a mini pedal that takes up almost no room on a board.
What it does
A conventional expression pedal sweeps continuously between a heel and toe position. The Cntl Knob replaces that sweep with two fixed points. You dial in the first value with the EXP 1 knob and the second with EXP 2, then step on the footswitch to jump between them. MusicRadar described the intended use as "instant access to two completely different pitches on a Whammy or two settings on your favourite delay pedal during songs"4.
GuitarPlayer noted that the Cntl Knob was the New York company's first-ever mini-pedal3, and it is small enough to slot into a gap on a crowded board: 3.63 x 1.75 x 1.50 inches1.
Controls
| Control | What it does |
|---|---|
| EXP 1 knob | Sets the first expression setting; fully counter-clockwise is the heel position, fully clockwise the toe position1 |
| EXP 2 knob | Sets the second expression setting, mapped the same way1 |
| Footswitch | A press toggles the active expression setting on EXP OUT between EXP 1 and EXP 21 |
| TRS +/- button | Inward, the EXP OUT polarity is Ring-to-Wiper; outward, it is Tip-to-Wiper1 |
| LEDs | Each EXP knob has an associated LED showing which setting is currently active2 |
Guitar World's reviewer, Trevor Curwen, explained the knob mapping: "the fully anti-clockwise start point represents the heel-down position of an expression pedal, while the fully right clockwise position is the toe", covering the full 0 to 127 range or any two values in between2.
Connections and power
The Cntl Knob has a single output, a standard Exp Out jack, and Electro-Harmonix states that a TRS (tip-ring-sleeve) cable is required to connect it to the controlled device1. The TRS +/- button handles polarity: some devices expect Ring-to-Wiper wiring, others Tip-to-Wiper, and the button flips between the two1.
The pedal runs on a 9V DC adaptor and draws 5mA12. There is no battery option, but the low current draw means it can share a standard power supply output on most boards.
Versions and alternatives
Electro-Harmonix's expression range includes several conventional rocking pedals the Cntl Knob sits apart from: the EHX Expression, a single-output pedal with a range knob and reverse button, and the Dual Expression Pedal, which controls two devices at once. The Cntl Knob is the odd one out: no moving parts, no sweep, just two stored values and a switch123.
What reviewers said
Guitar World's verdict was positive: "An inexpensive, clever utility stompbox that will expand your pedalboard possibilities while saving space."2
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Questions
What does the Electro-Harmonix Cntl Knob do?
It is a static expression pedal: instead of rocking a pedal back and forth, you set two preset values with the EXP 1 and EXP 2 knobs, representing two positions of a traditional expression pedal, and the footswitch toggles between them on the EXP OUT jack. It gives instant access to two settings on any device with an expression control jack, such as two pitches on a Whammy or two settings on a delay pedal.
Does the Cntl Knob need a TRS cable?
Yes. Electro-Harmonix states that the EXP OUT jack requires a TRS (tip-ring-sleeve) cable to connect to the expression control jack of the device you are controlling. A standard mono guitar cable will not carry the expression signal correctly.
What does the TRS +/- button do on the Cntl Knob?
It sets the polarity of the EXP OUT jack. With the button pressed inward, the polarity is Ring-to-Wiper; with it outward, the polarity is Tip-to-Wiper. That lets the Cntl Knob match devices that wire their expression jacks in different ways.
Can the Cntl Knob run on a battery?
No. The pedal is powered from a 9V DC adaptor and draws 5mA. There is no battery option, though the low current draw means it can share a standard pedalboard power supply output.
Does the Cntl Knob work with a Whammy pedal?
Yes. MusicRadar describes the intended use as instant access to two completely different pitches on a Whammy, or two settings on a favourite delay pedal, during songs. Any device with an expression control jack is a candidate.
Where is the Cntl Knob made?
The Cntl Knob is made in the USA, according to Guitar World's review, which lists its origin as USA.
Sources (4)
- Cntl Knob, Electro-Harmonix
- Electro-Harmonix Cntl Knob review, Guitar World, 2021-04-15
- Electro-Harmonix Announces New Cntl Knob Static Expression Pedal, GuitarPlayer, 2020-07-08
- Electro-Harmonix reveals its… Cntl Knob?!, MusicRadar, 2020-07-10
