Up close with the ultimate Dumble Overdrive Special Jason Isbell calls “possibly the greatest amplifier ever made"

Dumble Overdrive Special
(Image credit: Vertex Effects / YouTube)

California pedal brand Vertex Effects got the chance to get up close and investigate a rare Dumble Overdrive Special guitar amp – an unlabelled example that has since been bought (and used onstage) by Jason Isbell. But why has he called it "possibly the greatest amp ever made"? Because this might be the ultimate Dumble, and this video explains why. 

Vertex Effects' Mason Marangella is a huge admirer of the late Howard Alexander Dumble's work, and this amp (serial number 22) is very, very special. He is joined by Gabriel Bergman at Techno Empire in Burbank. Between them they've played several Dumble amps before and "none come close to this one".

Both men are clearly excited by just how good it is – and in the video above they really dig into why Dumbles are so coveted. Gabriel has a 2012 '59 reissue Les Paul to try with the amp, and Mason uses and Strat, along with a Tele. 

The pedalboard they use for trying out the Overdrive Special is fairly minimal, including a Vertex Boost (as used by Robben Ford with his own Dumble), TC Hall OF Fame reverb Mini and Strymon Timeline. They use a Ceriatone Kleinulator (a solid-state version of a Dumbleator) level adjustable effects loop buffer pedal to drive the time-based effects without losing tonal goodness. 

In a strange twist, serial number 22 isn't listed in the Dumble Book – the tome that records all the known serial numbers Howard made. As Mason notes, it jumps from 21 to 23. It was a one-owner amp with producer and session guitarist Dennis Herring… until now. 

Former Bonnie Raitt guitarist Herring is one of a coveted group of players chosen by Dumble to be a customer, as he recounts in the video above. 

"If I was still doing sessions, there's no way I would part with that," says Herring. 


Watch and enjoy, then check out the clip of its new owner Isbell putting it to spectacular use on his song King Of Oklahoma live below.

Rob Laing
Guitars Editor, MusicRadar

I'm the Guitars Editor for MusicRadar, handling news, reviews, features, tuition, advice for the strings side of the site and everything in between. Before MusicRadar I worked on guitar magazines for 15 years, including Editor of Total Guitar in the UK. When I'm not rejigging pedalboards I'm usually thinking about rejigging pedalboards.