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Dumble amp clone

As mentioned on the biography page, Alexander "Howard" Dumble passed away in 2022, and it can be safely said that he "took the secret of his amplifiers' tone to the grave...". Most brands that clone Dumble amplifiers continuously strive to achieve a 1:1 match of the tone from the Overdrive Special or Steel String Singer models. Is that even possible? In our opinion, both yes and no... For many years, enthusiasts of this "creamy" tone possessed only guesswork and fragmentary information about the flagship Overdrive Special model. Everyone wondered exactly what components Dumble used and what their topology looked like.
The breakthrough occurred on The Amp Garage forum in early 2008, when the first fully documented and scratch-drawn schematic of the iconic Dumble ODS #124 was published. In 2006, the amplifier with serial number #124 - originally built in 1984 and later updated (modified) by Alexander Dumble in 1988 - belonged to the esteemed Los Angeles session guitarist, Thom Rotella. When the gear needed servicing, it ended up in the hands of amp technician Billy Yates. Alexander Dumble was notorious for covering critical sections of his circuits (especially the preamp and tone stack) in blue or black epoxy ("goop") to prevent reverse engineering and hide component values. To perform full maintenance, a re-cap, and necessary repairs, Billy Yates had to painstakingly remove this epoxy. After cleaning the circuit board (PCB), Billy Yates and Rob Livesey took highly detailed photographs of the chassis interior and the circuit itself. As Livesey himself confirmed on the forum, these photos were taken while the amp was in Yates's shop for service, right before it hit the used market. It was these legendary photos and measurements that later made their way online.
We described the history of the Steel String Singer's development here. 

Interior of the Dumble Overdrive Special #0189, showing the distinctive blue epoxy resin - photo from ampgarage.com

What are the problems with Dumble amp cloning?

While having a schematic is a great starting point, achieving a true 1:1 match of the genuine Dumble amplifier tone comes with several hurdles that go far beyond just soldering the right components onto a board. I truly realized this only when I heard an original Overdrive Special, serial number #031, from a distance of literally one meter at the Guitar Summit show! As an exhibitor, I was fortunate enough to be invited by Udo Pipper - a renowned expert and Dumble amplifier owner - to his workshop, where this specific unit (#031) was featured. Before the workshop started, Udo compared my D-TONE Overdrive Specialist (which is based on the #102 specification) with the original ODS #031. Despite the difference in their circuits, he was genuinely surprised - as was I - by just how close my replica got to that legendary, "creamy" tone. Of course, the differences were audible - primarily in the sustain, which these amplifiers are so famous for. Where, then, does the problem lie? First and foremost, It is important to note that each unit was created for a specific owner and was perfectly tuned. As we wrote on the biography page, before Dumble built a specific unit, he conducted an in-depth interview regarding the guitarist's expectations, their playing style, and their instruments. One must therefore realize that due to the very nature of Dumble amplifiers, they are not a one-size-fits-all solution for every player. Udo Pipper perfectly demonstrated this to me during my private visit to his home, where he had two original Overdrive Special units at his disposal. He owned a few incredibly well-selected Gibson Les Paul guitars that were perfectly matched to those specific amplifiers. Another crucial factor is the player's touch - the ability to physically evoke that famous, "violin-like" sustain. Many musicians are convinced that you can simply plug a guitar into a Dumble, and the amplifier will do all the heavy lifting for you... That is absolutely not the case. These are amplifiers built for highly discerning, expressive players who possess the technical ability to pull "that special something" out of the circuit with their own fingers - a quality that no other amplifier can replicate.

Udo Pipper compares an original Dumble Overdrive Special #0031
with the D-Tone Amps Overdrive Specialist

Another crucial factor was Dumble's specific component selection:

1. Iconic Schumacher Transformers: The transformer is essentially the "heart and lungs" of a tube amplifier's dynamic response. It dictates how the power supply reacts when you strike the strings with more force. In his builds, Dumble frequently used vintage transformers salvaged directly from Fender amplifiers. For the ODS model, this was typically a Bassman 50W transformer, while for the SSS, it was from a Twin Reverb. These components were characterized by a specific voltage drop - known as sag - which had a direct impact on the tone and natural sound compression. Very few modern, commercially produced components possess this unique quality. When selecting components for D-TONE amplifiers, this was exactly our primary criterion. After rigorously testing products from various manufacturers, we chose the Tube Amp Doctor (TAD) brand. They are manufactured in the USA strictly according to the vintage Fender specifications, ensuring an identical core structure and electrical parameters.
2. Component Drift and 40 Years of Aging: Vintage components, such as Sprague Orange Drop capacitors, Sprague Atom electrolytic capacitors, or Piher carbon film resistors, change their actual electrical values over decades due to heat and chemical processes. This phenomenon is known as component drift. Even if a modern boutique manufacturer sources the exact same brand and nominal factory value specified on an old schematic, a brand-new component will measure and sound completely different from a part that has been gently "baking" inside the hot chassis of an original amplifier for forty years. No manufacturer can overcome this phenomenon - not even Two-Rock or Amplified Nation...
3. The RoHS Directive: Adopted in 2003 and taking effect in 2006, the RoHS Directive aimed to restrict the amount of hazardous substances - primarily heavy metals - entering the environment from electrical and electronic waste. The implementation of these regulations largely eliminated the use of many highly sought-after vintage components in their original formats. One must realize that Dumble primarily used components containing lead, which was standard practice during the era when he was building his amplifiers: 
Transformers: Original Schumacher transformers from Fenders contained lead in their insulation and leads.
Resistors: Piher/Beyschlag, Mepco/Electra, and vintage military-grade Vishay Dale RN65 - all featured leads coated with a tin-lead (Sn-Pb) alloy.
Capacitors: Sprague Orange Drop PS series and Atom series - all featured leads coated with a tin-lead (Sn-Pb) alloy.
Potentiometers and switches: CTS and Carling components from that era contained lead within their internal factory connections and housing plating.
If Mr. Dumble were to start building his amplifiers today, he would be forced to use completely different types of solder (such as lead-free solder, which requires higher temperatures during the soldering process) as well as modern, lead-free revisions of the aforementioned components. Unfortunately, both in Europe and in the USA, there are no exceptions here for manufacturers. Non-compliance with RoHS carries severe penalties, so any discerning builder will not risk selling amplifiers with components that contain prohibited amounts of lead, even if those original vintage parts sound superior. Fortunately, lawmakers included an official exemption for vacuum tubes themselves, allowing the use of lead within them as no technological alternative currently exists. Without this specific clause, every single amplifier produced today would have to be solid-state. Is there an alternative to components that do not meet RoHS standards? Yes - today there are many high-quality replacements that get 99% close to what Dumble originally used. Of course, there is always that remaining 1% of voodoo...
4. Chassis Layout and Stray Capacitance: In high-voltage, high-sensitivity tube circuits, the physical placement of the wires - known in the amplifier world as lead dress - is of critical importance. Wires running parallel to each other or too close to the chassis act like tiny, invisible, unintended capacitors (stray capacitance). Dumble was an absolute master of this; he spent countless hours manually tweaking the exact routing and angle of every single wire by ear, while listening to the noise floor and unwanted hum. Copying a two-dimensional schematic diagram is simple, but capturing the complex three-dimensional spatial interaction of the physical wiring inside the chassis is a massive challenge for any builder.

Interior of the Dumble Overdrive Special (2nd Generation), showing the internal components.

Best D-Style amp for sale

Few can afford an original Dumble amplifier, such as the Overdrive Special or Steel String Singer. So what are our alternatives? We can take two paths: buy a zero-compromise replica (or a clone, if you prefer) that sounds as close to the original as possible, or purchase a boutique amplifier that merely nods to that character, such as a Two-Rock or Amplified Nation. There is also a third way, which we strongly advise against - buying a DIY amplifier kit to assemble it yourself. These types of kits provide nothing more than a raw foundation. To make such an amplifier perform correctly, it almost always requires deep modifications, which demands extensive technical knowledge and years of experience. Which path to choose, and does a perfect replica even exist? We hope that the information across our website will convince you to choose a premium replica, such as D-TONE AMPS. Of course, we will never convince the skeptics and die-hard voodoo believers - even if they were to take part in blind tests, they would mistake our amplifier for a real Dumble. But that is not our goal. We want everyone reading our text to realize that the Dumble tone is not just about the circuit itself, but also about the player's awareness and unique touch. Not every Dumble amplifier will work in the hands of a given musician, and not every guitarist will sound like a Dumble on a Dumble. What, then, sets us apart from other brands? Unlike 99% of the companies building replicas, we at D-TONE AMPS have had direct, hands-on experience with an actual, physical Dumble amplifier, rather than just relying on its online schematics. This firsthand experience, combined with the invaluable assistance of Udo Pipper, has allowed us to create clones that sound incredibly close to the real thing. It is safe to say that these are the best D-Style amplifiers available on the market today...

Overdrive Specialist by D-TONE AMPS - head + 1x12" matched cabinet