The Carl Martin Optical Envelope Filter is an envelope filter pedal, the kind of effect players know as an auto-wah: it opens and closes a filter automatically in response to how hard you pick, rather than waiting on your foot. Carl Martin describes its Classic Optical Envelope as "a versatile auto-wah/envelope filter pedal utilizing premium opto-technology"1. Premier Guitar's review notes that the filtering is done with an analog optical circuit, so the wave envelope is manipulated optically rather than digitally2.
What it does
An envelope filter tracks the dynamics of your playing and sweeps a filter accordingly: pick harder and the filter opens further. Premier Guitar described the pedal as working "brilliantly" on that account, calling it "Carl Martin's new envelope filter"2. Because the response follows your attack, the effect sits naturally in funk, psych and percussive rhythm playing, and the same design was pitched for bass as well as guitar when it was released3.
The circuit borrows from another pedal in the company's range: when the Classic Optical Envelope was unveiled in 2011, MusicRadar reported it as an auto-wah "utilizing the same opto-technology as the Opto-compressor"4.
Controls
| Control | What it does |
|---|---|
| Select switch | Alternates between three presets5 |
| Drive | Dictates how sensitive the effect is to your picking attack5; controls how much the auto-wah works3 |
| Tone | Acts as a separate hi-pass filter4 |
| Q | Adjusts the bandwidth of the filter3 |
One thing to know before you start turning knobs: the controls are not independent. Carl Martin states that "All controls on the Classic Optical Envelope work interactively with each other, meaning adjustments to one parameter may" require re-tweaking the others1. In practice that means setting the pedal is a matter of balancing drive, tone and Q against each other rather than dialing each one in isolation.
The pedal is built into a diecast housing3.
Price and value
Premier Guitar's review listed a street price of $1352. The reviewer's verdict was favorable on value as well as sound:
"Given the low price, solid build, and smooth, versatile sounds, anyone on a budget that's looking for the distinctive so..."2
Premier Guitar summed the pedal up as great value, with the low price, solid build and smooth, versatile sounds making it a pick for budget players wanting envelope filter sounds2. The pedal carried a street price of $1352.
The Ottawa: the redesigned successor
In September 2021, Carl Martin announced the Ottawa Vintage Optical Envelope filter, which Guitar World described as "a beefed-up version of the brand's pre-existing Optical Envelope Filter"6. It is a compact modulation pedal aiming to deliver psych-inspired auto-pilot wah sounds, "ranging from '60s psych sounds to '70s disco tones"6. Its Q control knob adjusts the bandwidth of the Ottawa's filter6.
The Classic Optical Envelope and the Ottawa are two different pedals from the same maker. If you are comparing the two, the Ottawa is the later redesign of the original Optical Envelope Filter design6.
For more on this family of effects, see the site's pages on filter pedals, the Carl Martin Classic Optical Envelope and the Carl Martin Ottawa.
Videos
Carl Martin
Iga Massardi
Selane Productions
Questions
What is the Carl Martin Optical Envelope Filter?
It is an auto-wah and envelope filter pedal from the Danish maker Carl Martin. It uses an analog optical circuit to move a filter in response to your picking attack, and its drive, tone and Q controls let you shape how sensitive the effect is, how much high end passes through, and how wide the filter's bandwidth is.
Is the Ottawa the same pedal as the Classic Optical Envelope?
No. The Ottawa Vintage Optical Envelope filter, released in 2021, is a beefed-up, redesigned version of the earlier Classic Optical Envelope. Guitar World described it as a compact modulation pedal aiming for psych-inspired auto-pilot wah sounds, ranging from '60s psych to '70s disco tones, with a Q control that adjusts the bandwidth of the filter.
Sources (6)
- Classic Optical Envelope, Carl Martin, 2026
- Carl Martin Optical Envelope Filter Pedal Review, Premier Guitar, 2012-05-02
- Carl Martin Releases Classic Optical Envelope Pedal, No Treble, 2011-03-17
- Carl Martin unveils Classic Optical Envelope and Blue Ranger FX pedals, MusicRadar, 2011-03-10
- Carl Martin Classic Optical Envelope review, MusicRadar, 2012-05-31
- Carl Martin debuts streamlined Ottawa Vintage Optical Envelope filter pedal, Guitar World, 2021-09-22
