Skip to main content

Carl Martin Ottawa Vintage Optical Envelope review

This cunningly named auto-wah offers a wealth of classic Mutron-esque tones

Carl Martin Ottawa
(Image: © Future)

Our Verdict

Classic auto-wah and envelope filter for clean sounds or feeding a dirt pedal.


  • Superb sounds.
  • Compact form and top-mounted jacks.


  • Nothing.

The long-established Danish brand Carl Martin refreshed its pedal lineup in 2018. Slick-looking anodized enclosures were the order of the day, with pedalboard placement made easier via top-mounted input and output jacks. 

Among these was the Ottawa, a redesign of the Classic Optical Envelope, and it runs with a standard nine-volt supply that connects on the top edge of the pedal, next to the input and output jacks.

Ottawa? We wondered why this pedal was named after a Canadian city until we said it out loud – ‘Auto Wah’! Yes, this is an old-style envelope in the Mutron vein. 

The Level knob sets the output level, but the other three knobs define the effect’s intensity and tonal quality: the Attack knob sets sensitivity to your pickups and playing dynamics; the Tone knob progressively filters out high frequencies affecting the tonal ballpark of the effect; and the Q knob adjusts the bandwidth from something soft and rounded to sharper and more dramatic, typically from a ‘wah’ to a more pronounced ‘wow’. 

Filter type is selectable. Band Pass offers a more conventional wah, High Pass loses body for a scratchier funk sound, while Low Pass is warmer and fuller. Whether it’s tight rhythmic wah or quacky/vowel-y single notes, it’s all dialled in easily here.  


  • PRICE: £119
  • ORIGIN: China
  • TYPE: Envelope pedal
  • FEATURES: Buffered bypass
  • CONTROLS: Tone, Attack, Q, Level,
    HP/BP/LP switch, Bypass footswitch
  • CONNECTIONS: Standard input,
    standard output
  • POWER: 9V DC adaptor (not supplied)
  • DIMENSIONS: 60 (w) x 115 (d) x 50mm (h)
  • CONTACT: Carl Martin

Thank you for reading 5 articles this month*

Join now for unlimited access

US pricing $3.99 per month or $39.00 per year

UK pricing £2.99 per month or £29.00 per year 

Europe pricing €3.49 per month or €34.00 per year

*Read 5 free articles per month without a subscription

Join now for unlimited access

Prices from £2.99/$3.99/€3.49

Trevor Curwen has played guitar for several decades – he's also mimed it on the UK's Top of the Pops. Much of his working life, though, has been spent behind the mixing desk, during which time he has built up a solid collection of the guitars, amps and pedals needed to cover just about any studio session. He writes pedal reviews for Guitarist and has contributed to Total Guitar, MusicRadar and Future Music among others.