He grew up in Bakersfield, California and as an 18 year old kid built amplifiers for Semie Mosely. And the Ventures used his amplifiers!
Along the way, he changed his name to Alexander and went on to build some of the most desirable and expensive guitar amplifiers ever made. He was modifying Fender amps and began making his own guitar amplifiers in the late 1960’s in Santa Cruz. Dumble was one of the first boutique amplifier manufacturers. There are possibly only 300 Dumble amplifiers, so the prices are at a premium.
Dumbles are used by such artists as Carlos Santana, John Mayer, Robben Ford, Larry Carlton, Eric Johnson, Stevie Ray Vaughan, Ben Harper, Lowell George, Steve Lukather, Sonny Landreth, Jackson Browne and David Lindley.
In a 1985 Guitar Player article it was stated that Dumble amplifiers were selling for as much as $5,000. You couldn’t touch one today for $15,000.
They are manufactured for rock music and are tweaked to have a very sweet sounding distortion. Dumble uses only the best electronics in his amplifiers. I read that he often covered the plate resistors and capacitors in silicon or epoxy to prevent others from mimicing his proprietory technology. Despite these precautions, there are a handful of companies that provide Dumble DIY clones. And other companies sell guitar amplifiers based on Dumble’s circuits.
Dumble makes different models and will customize the amp to fit the artist.
The most well known is:
The Overdrive Special.
The 50 watt Overdrive Special Combo features two inputs. One is normal and the second is a FET input. This input sends the signal through a J-FET line-level preamplifier before entering the first tube stage. The intended purpose of this was for use with acoustic guitars or low impedence signals.
Controls include Bright, Deep, Midrange, Boost (by disconnecting the treble and bass potentiometers, this gives the preamp more power.) A Rock/Jazz switch changes the voicing. Through the use of differing preamp circuits, Dumble amps can provide a clean tone or a singing distorted tone. Think David Lindley with Jackson Browne.
It has similar circuitry to the Overdrive Special, however the reverb section utilizes 3 tubes in a method that would be similar to Fender's stand alone unit, however it is more advanced since the reverb send and reverb return mix with a clean dry signal. This provides much more control than other amplifiers.
The Steel String Singer
Stevie Ray Vaughn used a specially made model of this amp as a clean amp. It was rated at 150 watts with 4 6L6 power tubes pushing it. It was very loud.
This 300 watt amplifier known as the DUMBLELAND 300SL use unusual tube combinations. Six 6550A beam power pentode output tubes) power tubes were driven by a 12BH7 as a direct coupled cathode follower. The features and inputs are similar to the Overdrive Special, however the front panel controls include two rotary switch controls labeled as tone expander/ tonefilter and controls for reverb.
Depending on specifications, the rear panel may include a bias and dynamic balance controls. A speaker ohm control for 2, 4 or 8 ohms. Some Dumble amps come with tremolo.
This is 220 watt bass amplifier is named after the San Francisco dance hall run by Bill Graham and home to many outstanding concerts.