Monday, June 21, 2010

Dumble Amplifiers

While the rest of us were learning about first year algebra, a very young Howard Dumble was assembling homemade transistor radios and selling them to classmates for five bucks a pop. He states that he came from an engineering family and could read circuits about the same time he was reading sixth grade English. He built a 200 watt public address system for his schools junior baseball team. (If it’s still in operation it may be worth a small fortune.)

Dumble Overdrive Special
He grew up in Bakersfield, California and as an 18 year old kid built amplifiers for Semie Mosely. And the Ventures used his amplifiers!

Dumble Overdrive Special
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.

The amps are made using aluminum chasis. The finest shielded wiring is utilized.  The lead dress is perfect on the eyelet boards.

Dumble uses the best transformers.  For speakers he prefers ElectroVoice, Altec Lansing and JBL speakers.  These are top of the line.

Dumble makes different models and will customize the amp to fit the artist.

The most well known Dumble amp is he 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.

The Dumble Overdrive Reverb 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. The one above belongs to Carlos Santana.

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.

Dumble Winterland
This is 220 watt bass amplifier is named Winterland after the San Francisco dance hall run by Bill Graham and home to many outstanding concerts.
©UniqueGuitar Publications (text only)


Prizm said...

EAV Pro Audio stock a wide range of PA Speakers, Mixing desk, power amp, audio interfaces, projector lamp, Wireless microphones and wired microphones along with a massive range of home and professional recording equipment.

Miss Canan Akturk said...

sad that after all his great accomplishments the only video we have of him is this one which is over shadowed by a weird guitarist making weird noises.

Anonymous said...

Miss Canan hit the nail right on the head. Been playing (a guitar)since 15, not to mention my prior and post classical training (thank you for your inspiration Albert King). And I think Henry Kaiser is the most god awful thing I've ever heard and I'm now 57.

JBL Speakers Amplifier said...

Dumble was one of the first boutique amplifier manufacturers. ...

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