The Pete Cornish TB-83 Extra Duplex is a two-channel treble booster: two of the company's vintage treble boost circuits, each with its own output volume, built into a single enclosure. Pete Cornish lists it as "2 X VINTAGE TREBLE BOOST +O/P VOL"1. It belongs to the same family as the single-channel Pete Cornish TB-83 and Pete Cornish TB-83 Extra, and sits in the broader field of boost pedals.
What it does
The idea is simple and aimed at live playing:
- Set each side to a different volume and you have two degrees of boost on tap
- Switch both in together and the two circuits combine for up to double the gain of either one alone
- The same box can also be configured as the TB-83 and TB-83 Extra combination2
The Extra side exists because players wanted more than the standard TB-83 could give. Pete Cornish describes the TB-83 Extra as designed to complement the TB-83, giving a louder boost with more "bite" to bring solos above other instruments in live or recording work2.
Where it came from
The treble boost design behind it dates to the early 1970s. Pete Cornish's product page states this is the second treble boost he designed and built from that period and that it is still in production, hand made by Pete, Lynda and Mingus Cornish3. The original intended use was between the guitar and the "Normal" input of early Vox AC30s, to improve the tone and overdrive characteristics of that low gain type of amp by adding some "dirt" and "bite"3.
The family, as Pete Cornish offers it:
| Pedal | Circuits |
|---|---|
| Pete Cornish TB-83 | One vintage treble boost |
| Pete Cornish TB-83 Extra | One vintage treble boost, louder with more bite |
| TB-83 Extra Duplex | Two vintage treble boost circuits, each with output volume1 |
Build and power
The active circuitry is potted in semi-flexible resin, which Pete Cornish describes as vital protection against the environment and as a way to eliminate microphonic feedback2. On the related TB-83, reviewers Mark Reynolds and Martin Pitcher noted that the input jack socket activates the battery, so removing the jack plug when not in use saves battery life4.
The Duplex carries two boost circuits in one enclosure, so it draws on the same battery arrangement as the single TB-83 units; unplugging the input when the pedal is not in use preserves the battery4.
What reviewers said
The single TB-83 has drawn strong words from reviewers. Mark Reynolds and Martin Pitcher wrote4:
"This must be the most powerful treble booster we have ever tried."
Videos
Simon Gotthelf Music
Martin Klaja's Guitarchannel
That Pedal Show
Sources (4)
- Battery Free Effects Pedals, petecornish.co.uk, 2026-03-31
- Pete Cornish Vintage Series, Pete Cornish (petecornish.co.uk), 2026
- PETE CORNISH TB-83 Extra, Pete Cornish, 2023
- PETE CORNISH: TB-83 Review, petecornish.co.uk, 2025
