Other than building your own D-style amp, there are other simpler and less expensive ways in which you can edge closer to that dark, smooth overdrive.
Behind the Dumble mystique, there’s the reality of an amp that’s tricky to set up because of the cascaded gain topology, with a narrow window for optimum results. Originals were individually tuned by Dumble for their respective owners, so the narrower adjustment range was presumably less of an issue.
It would be unfair to call the Dumble a one-trick pony, though, as the sounds most people associate with them fit a wide range of musical genres. If you want those sounds - and assuming you can’t afford to buy an original at £75k a pop - there are several ‘clone’ amps offering similar tones and functions, but they aren’t thick on the ground and most are expensive. So, how to approximate that sound on a budget?
If digital modelling appeals, Vox’s affordable and very popular Valvetronix VT range features its Boutique OD and Boutique CLN models, which owe much of their inspiration to the Dumble tone. Prices start at around £170, which is seriously great value for money. If you just need the software, then there are several VST plugins that will get you into the D-sound ballpark - check out Scuffham, IK Multimedia and Positive Grid.
The next step up in this scenario is to combine a good valve amp with one of the many high-quality pedals claiming to replicate that sound.
One of the best and most popular is Lovepedal’s Zendrive, which sells for around £185. Designed by pedal guru Alfonso Hermida, the Zendrive was reputedly inspired by Robben Ford’s legendary Dumble tone and is so good that Ford himself has used it as a Dumble substitute, usually plugged into a Twin Reverb.
Other high-end pedals with similar sounds include Wampler’s superb Euphoria selling at around £190, and if money is even less important there’s Custom Tones’ superlative Ethos Overdrive, available to order direct, with prices starting at around $400. Coming back down to Earth, Hotone’s Grass Overdrive sells for around £55.
The key to getting the best from these pedals is an amp with a big clean sound. 6L6- or 6V6-powered designs such as Fender’s Hot Rod, Twin Reverb or Deluxe Reissues make great partners for pedals such as the Zendrive, but any amp with a good clean channel and reverb to sweeten the drive will get you in the ballpark.
Turn the valve
If you have a valve amp, one change worth trying that doesn’t need electronics skills is to substitute one or more 12AX7 preamp valves for Sovtek’s 12AX7WB.
It’s not so well known that there are three flavours of Sovtek’s 12AX7 twin triode. The ‘WA’ version is the standard model, used in many popular amplifiers; the ‘WC’ has closely matched halves and works best in the phase splitter position.
The interesting one is the ‘WB’ version, which is factory-selected for higher gain (typically up to six per cent over the WA) and characterised by a lifted bass response that translates into a darker tone with a smoother treble, compared with the ‘WA’ version.
12AX7WBs are standard in some high-end brands, including Rivera, Demeter and Kendrick. They sweeten otherwise harsh-sounding overdrive tones, warm up cleans, and help to better approximate the kind of smooth drive Dumbles are known for, particularly on Fender-style amps.
We recommend you carefully mark each valve and its position in your amp before experimenting with valve substitutions - different doesn’t always equate to better, so you need to be sure you can revert to your starting point. Also, bear in mind that bias adjustments are usually needed when changing power valves.