D-TONE AMPS D-Style sound

Dumble amp clone

As we wrote on this page about Mr. Dumble biography , he died in 2022 and we can say that "he took secret of sound of his amplifiers to the grave..." Most brand that Dumble clone amp aim to get 100% sound from Overdrive Special or Steel String Singer model. Is it possible at all? In our opinion, Yes and No... Although the schematics of Dumble amps are developed by many electronic engineers and available on Internet, we don't really know how Mr. Dumble got this specific sound, called "Dumble sound". This is a very obscure topic due to the small number of his products he has built himself, and very mysterious nature and personality of Mr. Dumble. In addition each of his amplifiers was non-series and slightly different. There is also a lot of unknown what components Mr. Dumble used to build Dumble amp circuit. When his reputation began to be noticed, he decided to cover preamp board inside of chassis with a thick layer of opaque epoxy resin, probably to prevent competition from copying layout and what components used.

On this page we describe exactly about Overdrive Special and Steel String Singer model.

Dumble Overdrive Special amp inside

*Original Dumble Overdrive Special amp inside - photo from:

www.reverb.com

What are problems in amp cloning?

I'm a guitarist with over 20 years of experience, I have been dealing with electronics for 15 years. In my "career" I had opportunity to play many amplifiers and guitars. At the beginning of my adventure with music, I used serial amplifiers such as Fender Tweed / Blackface and Marshall JCM series. Reissues, which are popular today, sounded great to me then, until I started having contact with old, often "tired", originals from the 60s. Paradoxically, despite identical models, those old that always sounded "warmer" and their distortion was more "round". Then I started to analyze their layouts and components and quickly came to the conclusion that reissues that use the cheapest components or poor quality tubes, will never sound "vintage". That's when I got the idea of cloning amps! I started with a relatively simple 5E3 model, popular Fender Tweed Deluxe. After running my 5E3 clone amp, I knew that my adventure with cloning would not end with just one amplifier... On this circuit, I learned principle of operation of tube circuits and how change in value of resistance or capacitance affects on sound. I modified the 5E3 circuit many times to get my sound. Then I did the same treatments in my clone Fender Princeton Reverb / Deluxe Reverb and Marshall JCM800 series. After cloning one channel amplifiers, it's time for two channel ones. I didn't want to clone Marshall's "diode" distortions, so I figured the Soldano SLO100 would be a good learning amp. This is an interesting layout, because the entire overdrive is purely tube based, channel switching is not done via relays, and FX loop is supported by an additional tube. Mike Soldano, inspired by the Mesa / Boogie MKII, created a "monster", which in turn was the progenitor of the Rectifier series - that's the story...

My private SLO100 clone - 50W version (not for sale)

*Mesa / Boogie MKII inside - photo from:

www.thegearpage.net

When I became a mature and conscious electronics engineer, I started my adventure with Dumble clone amps. At first, I was a bit put off, because after listening to presentations of various the Dumble Overdrive Special  / Steel String Singer clones on youtube, I came to conclusion that clones don't sound like original Dumbe amplifiers, for example, in Robben Ford's recordings... I started analizing at the Overdrive Special circuit and noticed that Mr. Dumble has used some non-standard solutions in several places on in his construction. Comparing schematics of the Dumble ODS amp to Soldano SLO100, it seemed simple to me, but I will immediately point out that my SLO100 clone was immediately sound good and the Dumble Overdrive Special clone was not... And here comes key question: what are the problems with cloning Dumble amplifiers? As I wrote before - it was not mass production and components used are not fully known, and if they are, they are largely unavailable. The 60s / 70s were a time when high-end components were generally available. The military industry moved away from use of tube circuits in favor of cheaper and less unreliable transistors. There was huge stocks of "military" resistors / capacitors and tubes that still work in Blackface amps to this day. Although there are many reissues of mustard capacitors or carbon resistors, they don't have such rigorous parameters as "military" ones. I believe that Mr. Dumble largely achieved this unique sound using "military toys". Another extremely important issue were transformers. There are no exact sources of what transformers he used in his amplifiers. From the analysis of the originals, these was most likely transformers from Fender amplifiers (manufactured at the time by the Schumacher brand). What about tubes? We know very well that "military" tubes are a completely "different world" than today. The military industry was very rigorous in terms of selection. How is today? We buy 10x ECC83 tubes, one of which doesn't work, two hum, and only one or two of the rest sound with a pleasant band... Of course, we can buy a set of purist NOS Mullard tubes, but they will cost around 1000 Euro and there are not that many of them on market. Finally, let's talk about speakers. Here it is similar to tubes - we buy 4 speakers, ex. Celestion G12-65 and each sounds a bit differently. This model is produced in the UK and is quite "equal", but, for ex., the Vintage 30 model is already made in China and can sound bad... It should be emphasized that new speaker starts to good sound only after about 1000 hours of loud playing! Suspension of membrane in new speaker are stiff and therefore don't work "freely", which makes its high frequency response unpleasant. Many purists seek at auction vintage speakers ex. Electro-Voice / Celestion, and those used in old Fender Blackface era amplifiers, realizing that they will always sound better than new speakers. Mr. Dumble has always used sophisticated speakers - often that are no longer available today. To sum up - there are many components that significantly affect the sound of the amplifier.

Is it possible to clone Dumble amplifiers well?

Yes but not in 100%. The "problems" described above show why this is so. Are there any solutions that will allow you to get closer to, say, 75-80% of the original? Our subjective answer: yes, but certain conditions must be met. First of all is most important thing is that, to start thinking like Alexander "Howard" Dumble, which is to try to get the best amplifiers sound possible with current components. In D-TONE AMPS we analyzed many Dumble Style amps clone and came to conclusion most companies cloning Dumble amplifiers, "stick too tightly" to parameters of resistance and capacitance from original Dumble amp circuit. So what if we build a preamp and power amplifier circuit cloning the ODS #102 number (Robben Ford model), if we have in market for only replacement transformers and the tubes are not NOS Mullard? And eternal question: carbon or metal film resistors? There are a lot of such questions and the more we ask them, more we realize that 1:1 cloning is not always good for final clone sound. For example, first D-TONE Dumble Style clone amp (prototype) was 1:1 clone, and didn't sound like Robben Ford at all...

D-TONE AMPS Dumble style amp clone

Overdrive Specialist by D-TONE AMPS inside - best Dumble Style amp

The knowledge gained while modifying amplifiers from Blackface era and JCM series, allowed our to make such changes to the parameters of resistance and capacitance in first D-TONE Dumble Style amp, that after few days modifying, it began to sound like a original the Dumble Overdrive Special amp! We spent a lot of time analyzing and selecting components. We would like to mention - modifications didn't consist in changing layout (because that's not what this is about), but only in changing some parameters of amplifier such as some capacitances of capacitors or voltages values of tubes and as well on selection brands of capacitors and resistors. We won't reveal our patents - it's not secret knowledge, but thanks to it we have an advantage over many electronics who build Dumble clone amps. To confirm our thinking, we recorded a comparison of the D-TONE Overdrive Specialist (based on Dumble Style amp) with original the Dumble Overdrive Special profiles on Kemper Profiler Powerrack, and it turned out that the sounds are practically the same, with the advantage of tube dynamics...

Overdrive Specialist by D-TONE AMPS - Dumble Style amp demo

We should also be mentioned issue of RoHS compliant, which was introduced in 2006 and aimed at reducing the amount of hazardous substances penetrating the environment from electrical and electronic waste - mainly heavy metals. The introduction of this directive has mostly excluded the use of NOS - type elements by guitar amplifier manufacturers, which simply don't meet this standard. If Mr. Dumble started building his amplifiers today, he would be doomed to use completely different components. Unfortunately, there are no exceptions here. For non compliance with RoHS, there are severe penalties for the manufacturer, so who is aware of this, doesn't risk selling amplifiers with components of unknown origin, even though they are better than those with the RoHS compliant. Fortunately, many of high quality components that meet RoHS compliant are current available - for ex.: Mallory capacitors or Xicon resistors. Fortunately, vacuum tubes have been exempted from RoHS compliant, because there is no substitute... Legislator came to his senses and didn't force manufacturers of guitar amplifiers to use "environmentally safe" transistors instead of tubes...

Is cloning legal?

In the case of the Dumble products, it is most justified. Mr. Dumble never founded a strict brand "Dumble amplifiers", but only signed his products with his name. After his death, there ware no official successor, who builded amplifiers under the name "by Dumble" and copyright his circuits. There will never be another original Dumble amp, because those made by Mr. Dumble had their "soul", which is impossible to clone... It remains for us to either buy an expensive and rarely available original or a good clone.

Best Dumble clone amp for sale

Few can afford an original to buy Dumble amp like Overdrive Special or Steel String Singer, so what other options do we have? We can go two ways: buy a Dumble clone amp as close as possible to the original, or buy an amplifier reminiscent of sound of Dumble guitar amp. There is also a third way, but we advise against him - buyed Dumble amp kit and assemble it yourself. This type of kit only provide a certain basis for clone amp - in the end, they often have to be modified and this requires a lot of experience. Personally, we a supporter of the first solution. There are several large brands on the world market that sell amplifiers like the Overdrive Special Style or Steel String Singer Dumble Style amp. These companies didn't want to create classic Dumble clone amps for sale by design, and therefore their sound is slightly different. Is it better/worse? It depends how close we want to be to the "Dumble sound". When it comes to clones that are as close to the original as possible, we have a lot of small manufacturers here, making amplifiers by themselves. As we wrote earlier - most of them "stick too tightly" to original values of resistance and capacitance from schematics, and therefore the sound of these clones is not entirely satisfactory. And this is what distinguishes D-TONE AMPS from other brands of this type. Tube guitar amplifier Overdrive Specialist and Steel String Singer by D-TONE AMPS are developed on basis of original schematics in such a way, that their sound is as close to the original as possible. We can be tempted to say that it is the best Dumble amp clone for sale today...

D-TONE AMPS Dumble style clone amps

Overdrive Specialist by D-TONE AMPS - best Dumble Style amps

best Dumble style clone amp

Overdrive Specialist by D-TONE AMPS - Dumble Style amps

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*D-TONE AMPS doesn't own of photos - we only shares them and not copy. Original source is under each photo.