Dumble musical instrument amplifiers are custom manufactured in very limited numbers by Alexander "Howard" Dumble of Los Angeles, California. Dumble amplifiers are among the most sought-after and expensive boutique amplifiers on the market; they were one of the originators of the modern boutique amp trend. The Dumble Overdrive Special was assessed as the most valuable guitar amplifier on the market, fetching on average between $28,000 and $35,000 a piece.
Dumble began modifying Fender tweed and blackface amplifiers in 1963 in Santa Cruz. By the late 1960s he was modifying and building high-gain amps in the way that Mesa Boogie and others did, but unlike them, Dumble was not really interested in the business of selling amplifiers in greater numbers, and became a "reclusive amp tech to the stars'".
Much of the company's PR is word of mouth, and Dumble builds his amps on special order. Carlos Santana, for instance, heard of Dumble in reference to Stevie Ray Vaughan and was lent one (it wasn't for sale); he "was hooked for life." After contacting Dumble himself, he was able to buy one, and then three more.
Dumble's German importer in the 1980s made a clone called the Kitty Hawk Standard. Since the 1980s, Dumble has covered the preamp circuitry of his amps with a thick layer of usually opaque epoxy, protecting his schematic's exact design.
Models and circuitry
Since Dumble's models were individually tailored, there aren't really distinct model lines with every amp of a certain model built with the same specifications. Nonetheless Dumble builds certain types with specific designations.
The Overdrive Special is built with 6L6 tubes, as an American-style amplifier (though he built some with EL34s like 183 which is extremely versatile and can even sound like a 6L6 at times, for a British sound it can be more aggressive also). Though originally based on a Fender blackface, it has evolved considerably. It uses 12AX7 tubes in the pre-amp section, and up to four gain stages for the lead channel.
Dumble also made a tube-buffered external effects loop called a Dumbleator. A few Dumble amps have a Dumbleator circuit built into them. The Dumbleator has separate "Send" and "Receive" circuit for the effects; a gain control, "Bright Switch" and a return level.
- Stephen Bruton (had a low-watt Dumble with 4 10" speakers)
- Larry Carlton
- Robben Ford (bought an Overdrive Special in 1983 and had a model custom-built in 1993/4)
- David Lindley (uses a Dumble cabinet)
- John Mayer (Steel String Singer)
- Lowell George (had an early custom Dumble head he used for most of his career.
- Carlos Santana (has an Overdrive Special and a Steel-String Singer besides his Mesa Boogies)
- Stevie Ray Vaughan (Steel String Singer)
- Henry Kaiser (1978 Dumble Overdrive Special) 
- Trainwreck Circuits, another manufacturer of boutique amplifiers
- Hunter, Dave (May 2011). "Robben Ford's '82 Dumble OD Special". Vintage Guitar. pp. 62–64.
- Hunter, Dave (June 2011). "25 Most Valuable Amplifiers". Vintage Guitar. pp. 38–40.
- Pittman, Aspen (2003). The Tube Amp Book: Histories, Specs and Schematics for Fender, Marshall, Vox, Ampeg, Gibson, Hiwatt, Mesa/Boogie, Matchless, Groove Tubes, Gretsch, Rivera, Dr. Z, Trainwreck and Many More. Hal Leonard. p. 13ff. ISBN 9780879307677. Retrieved 27 August 2012.
- Fjestad, Zachary R.; Fjestad, S. P. (2003). Blue Book of Guitar Amplifiers. Blue Book Publications. ISBN 9781886768420.
- Molenda, Michael (2010). Guitar Player Presents Carlos Santana. Hal Leonard. p. 77. ISBN 9780879309763.
- Falla, Jeffrey; Johnson, Aurora (2011). How to Hot Rod Your Fender Amp: Modifying Your Amplifier for Magical Tone. Voyageur. p. 143. ISBN 9780760338476.
- Moseley, Willie G. (May 2004). "Stephen Bruton In the Spirt of the Ft. Worth Tradition". Vintage Guitar. Retrieved 20 December 2011.
- Heidt, John (May 2001). "Larry Carlton: The Return of Mr. 335". Vintage Guitar. Retrieved 20 December 2011.
- Forte, Dan (August 2009). "Robben Ford". Vintage Guitar. Retrieved 20 December 2011.
- Forte, Dan (February 2007). "David Lindley: String Theory". Vintage Guitar. Retrieved 20 December 2011.
- Dirks, Rebecca. "Rig Rundown - John Mayer". Premier Guitar. Retrieved 9 June 2014.
- Kening, Dan (August 1976). "Lowell George of Little Feat". Guitar Player.
- Forte, Dan (April 2010). "Carlos Santana". Vintage Guitar. Retrieved 20 December 2011.
- "Stevie Ray Vaughan Rig". Guitar Geek.com. 2010. Retrieved 7 October 2013.
- "Henry Kaiser’s 5 Essential Effects". premierguitar.com. June 2013. Retrieved 4 May 2014.
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