The Vox Smooth Impact is a compressor pedal from Vox, part of the second series of the company's Valvenergy line of Nutube-powered effects. Vox describes it as an analog effect built around the Nutube, a compact vacuum tube, harnessing the non-linear realm of tubes with harmonics derived uniquely from vacuum tubes1. Its SAG mode provides natural compression and distortion similar to playing through a tube power amp, using Nutube distortion to reproduce sag1.
Where most compressor pedals shape dynamics with voltage-controlled amplifier circuits, the Smooth Impact does its work in the non-linear realm of tubes, with harmonics Vox says are derived uniquely from vacuum tubes1. It offers three compression modes, Vintage, Natural and Sag, chosen with a mini switch, and three knobs for the rest of the shaping1.
A Nutube compressor with three modes
The Smooth Impact is one of two pedals in the Valvenergy series that use a Nutube valve to generate dynamics and tone, the other being the Tone Sculptor EQ4. The Nutube is a vacuum tube in a compact package, and Vox says the pedal harnesses the non-linear behavior of tubes rather than emulating it, which is what sets it apart from typical pedal compressors1.
The three modes are the heart of the pedal, and each changes both the attack and release behavior and the character of the compression1:
| Mode | Attack / release | Character |
|---|---|---|
| VTG (Vintage) | Fast attack, slow release | Compression kicks in from the attack; a classic sound with extended sustain, effective for impactful cutting techniques1 |
| NAT (Natural) | Slow attack, fast release | Preserves the attack feel while providing compression; a natural playing experience that brings out nuances that may be subtle on high strings1 |
| SAG (Sagging) | Tube-amp style | Natural compression and distortion like a tube power amp, using Nutube distortion to reproduce sag1 |
Guitar World reported at launch that Vintage is said to be a traditional compressor perfect for pop and country5. Vox positions the pedal's solid sound with a light touch as highly effective for players who are not fans of compressors, and for modern-style clean-tone backing and tapping1.
The controls: Tube Gain, Comp, Output and the mode switch
The control set is deliberately small: three knobs and a three-way toggle6. What the knobs do, per Vox1:
| Control | What it does |
|---|---|
| Tube Gain | Sets the tube gain; interacts with the Comp knob to adjust the texture of compression1 |
| Comp | Controls the compression level; adjusts the texture of compression through interaction with Tube Gain1 |
| Output | Adjusts the output volume1 |
| Mini switch | Selects one of the three modes based on your preference and the situation1 |
Dave Hunter, reviewing for Guitar Player, described the toggle as a three-way voicing and feel switch delivering Vintage, Natural or Sag3. One thing the pedal does not have is variable attack and release controls; Premier Guitar's reviewer noted it lacks these familiar features, because the mode switch handles that job instead4.
Power and connections
The pedal runs on a DC 9V AC adapter or 9V alkaline batteries (6LF22/6LR62), and both are sold separately. The adapter Vox lists is the KA181 (9V). If you prefer batteries, Vox recommends the alkaline type1.
Neither the adapter nor batteries come in the box. If you plan to run the Smooth Impact on a pedalboard power supply, it uses a DC 9V terminal1.
Connections are simple: a monaural phone jack input, a monaural phone jack output, and the DC 9V terminal1. When the effect is deactivated, the Nutube functions as a buffered bypass, which Vox says provides a natural response and a light feel; the pedal also uses a newly developed dedicated buffer circuit at its initial stage1. So this is not a true bypass pedal, and the buffer is part of the design rather than an afterthought.
The chassis itself carries an etched top panel design inspired by the unique sound of each effect pedal in the series1.
What reviewers said
Published reviewers generally found the Smooth Impact to be a natural-sounding compressor with a distinct personality, with some caveats about subtlety and extreme settings634.
Guitar World's reviewer found the compression effects sound especially natural without any pumping or squashed textures6. Dave Hunter at Guitar Player called it an effective comp benefitting from three feel and voice modes, a good-sounding rendition with an appealing personality that does well at its price point, while noting it is possibly a touch subtle for those seeking more colored compression, and not as overtly colored or characterful as some of the most-revered units on the market3.
"I enjoyed the Smooth Impact most in its in-between ranges, where mass, mild, harmonious drive, and low noise showcase the pedal's sometimes studio-like personality."
Premier Guitar's reviewer also found that at higher compression levels it can sound snappy, crisp and tight without feeling like you have bled every trace of overtone from your signal, and that the sag mode's compression is more like what you get from tube saturation, useful for adding thickness and complexity to a thin amp tone at modest compression levels4. The same review flagged the limits of the extreme settings: at the most aggressive settings the tube gain can get a little crispy, and really crushing the compression can flatline your tone without adding much extra sustain4.
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Questions
Does the Vox Smooth Impact run on a 9V battery?
Yes. Vox specifies 9V alkaline batteries (6LF22/6LR62) or a DC 9V AC adapter, and both are sold separately. If you use batteries, Vox recommends the alkaline type. The adapter Vox lists is the KA181 (9V).
Is the Vox Smooth Impact true bypass?
No. When the effect is deactivated, the Nutube functions as a buffered bypass, which Vox says provides a natural response and a light feel. The pedal also uses a newly developed dedicated buffer circuit at its initial stage.
What does the Sag mode on the Smooth Impact do?
SAG (Sagging) mode provides natural compression and distortion similar to what you experience playing a tube amp, using Nutube distortion to reproduce sag. Vox says it is ideal for combining with transistor amps or digital modelers to bring out the essence of a tube amp.
Does the Vox Smooth Impact have a real tube in it?
Yes, in the form of a Nutube, a compact vacuum tube. Vox describes the Smooth Impact as a genuine vacuum tube compressor that uses the gain variation resulting from fluctuations in the Nutube, and calls it the first vacuum tube compressor in pedal form.
Sources (6)
- SMOOTH IMPACT, Vox Amps (voxamps.com), 2025-04-16
- Guitar Pedal X, Guitar Pedal X, 2024-01-25
- Vox Valvenergy pedals reviewed, GuitarPlayer (www.guitarplayer.com), 2024-11-11
- Vox Smooth Impact and Tone Sculptor Review, Premier Guitar, 2025-04-24
- Vox issues Valvenergy Power Burst, Tone Sculptor, Fuel Injector & Smooth Impact pedals, Guitar World, 2024-01-19
- Vox Valvenergy 2nd Series pedals review, Guitar World, 2025-01-02
