Dumble Overdrive Special Clone. 50w Hand Built Clone of ODS #40.

Alexander Dumble first began to build amplifiers in the late 60’s and has perhaps single handedly defined the term ‘boutique amp builder’. It is estimated that only approximately 300 original Dumble amplifiers were built by him. As such they are very rare and highly sought after, commanding well into five figures and sometimes over 6 figures.

Each Dumble amplifier was custom built and tweaked to suit the customers individual playing style and needs. So essentially no two Dumble amplifiers are exactly the same. However, there is a distinctive ‘Dumble sound’ that is common to most if not all Dumble Overdrive Specials.

The ‘Dumble sound’ could be described as 3 dimensional on clean settings with a wide dynamic range, amazing note definition and a shimmering top end which is very smooth. On the overdrive section there is a still a good dynamic range and note definition but also some added compression and a creamy mid-focused overdrive tone which allows the notes to bloom in a very attractive way, and sits well in any mix.

So is this clone of ODS #40 true to the ‘Dumble sound’? Yes we think so. Does it sound exactly like ODS #40? We don’t know – but it does sound great.

This clone was hand built by UK session musician and Dumble devotee Marcus Cliffe. Marcus has hand built a handful of Dumble clones mainly for his own use and occasionally for one or two of his name clients, so they rarely come up for sale. His Dumble clones have been used by the likes of Larry Carlton on a UK tour, and have also been used on stage with Eric Clapton and John Meyer at the Crossroads festival.

Here is a description of the build of this particular amp from Marcus Cliffe:

“The amp is a clone of a 2nd gen Dumble Overdrive Special serial number #40. A 50w 2x6L6 amp that was originally a combo.

All parts except the chassis were made bespoke for the amp. The chassis is an exact clone of the original and now no longer available.

The boards were made in brown garolite to match the original. The caps are orange drop 6ps like the original and the main plate resistors used were original NOS dale metal films as used in the original amp. These are like†unicorn tears now as there is very little NOS available anywhere in the world. The cabling is solid core like the original and the coax cable is the same thick coax Dumble used in the amps of this generation.

The transformers were hand made in Italy exactly to spec so the voltages would be correct. The modern addition was an extra secondary winding to power the relays rather than have an extra power transformer.

The main tweak to the amp is the addition of the FET boost as a footswitchable effect. The interior trim pot from the FET board has been relocated into the FET jack socket and it is now possible to switch the FET in and out on the footswitch along with the OD. The other addition is the grounding switch has been re purposed as a half power switch.

The amp runs 2x 12AX7 pre amp tubes for the normal and overdrive and the Phase Inverter utilises the AT7 as does the original, this can be swapped for a 12AX7 for more gain ’umph’. The output is 2x 6L6 tubes and is SS rectified.

The amp is pre classic tone stack with the following values:

Treble: 500KL pot / 510pF treble cap

100k slope resistor

Mid: 250KA pot / .01 mid cap

Bass: 1MA pot / .1 bass cap / .002 soldered between the terminals 2 and 3 of the bass pot and .02 cap soldered between terminals 1 and 2 of the bass pot / 10K tail.

The amp is now a separate head and is covered in traditional brown suede and black Vox grill cloth. There is a passive FX loop and an 8 and 16†ohm speaker output.

Marcus Cliffe - NorburyBrook Amps”

Audio samples below.

The following sound clips were were recorded with the Dumble clone going into a Two Notes Torpedo Captor X which was running a simulation of a Two Rock open back Dumble style 2x12 cabinet loaded with Scumback 12" M75-LD speakers.

These clips were recorded with a Fender Stratocaster and a Gibson Les Paul Special. Both guitars went straight into the amp with no pedals of any kind. The recorded signal was untreated in the DAW. There was a small amount of room ambience added on the Captor X going into the DAW. Any switching clicks you might hear between tunes is the changing of the pick up selector.

On the OD clips the FET boost switch was engaged during the ‘solos’.

*No neighbours were harmed during these recordings