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Dumble Amplifiers

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Dumble was a guitar amplifier manufacturer in Los Angeles, California.

A Dumble Overdrive Special

In the one-person operation, Alexander "Howard" Dumble (June 1, 1944 – January 16, 2022)[1][2] made each amp personally. Because of this, Dumble amplifiers are the most expensive boutique amplifiers on the used market,[3] and prices have risen rapidly. In 2012, Vintage Guitar magazine described the Dumble Overdrive Special as the most valuable in the product line, with used amplifiers fetching between $70,000 and $150,000.[4] Other examples have sold for more.[5]

Dumble built two or three amplifiers per year, primarily for celebrity musicians and studios. He priced them similarly to the used market to dissuade resale.[6] Dumble serviced and refurbished his original amplifiers for a fee, and many players would buy used Dumble amplifiers and have Dumble refurbish them. Carlos Santana and Ben Harper, for example, both bought their first Dumble used, and had Dumble refurbish the amp for their particular playing styles.[7]


Howard Alexander Dumble began modifying Fender tweed and blackface amplifiers[8] in 1963.[9] Before he was 21, Mosrite, in Santa Cruz, hired Dumble to build a special line of Amplifiers for The Ventures. By the late 1970s, he was modifying and building high-gain amps in the way that Randall Smith of Mesa Boogie, and others did. Dumble, however, was not interested in selling amplifiers in greater numbers, but focused solely on getting the best possible sound. Building to order only (even building his own speaker cabinets by hand), his amps gained a positive reputation and became highly sought after by professional musicians. Dumble became known as a tube electronics master, and his high end clientele gained him a reputation as a reclusive amplifier tech to the stars.[8]

Much of the company's PR over the years has been word of mouth. Howard Dumble did some interviews and advertisements in the 80s—but few people knew about him, even in the professional music community. Carlos Santana, for instance, only heard of Dumble in reference to Stevie Ray Vaughan in the late 90s. After someone loaned him an amplifier (it wasn't for sale) he "was hooked for life." He subsequently contacted Howard Dumble, and was able to buy a used amp and have Dumble refurbish it. Reportedly he has since bought more.[10]

Since the 1980s, Dumble covered the preamp circuitry of his amps with a thick layer of usually opaque epoxy, presumably protecting his circuit's exact design from prying eyes.[11] There are other practical reasons for covering circuits in epoxy: it keeps the parts firmly in place, and specially formulated epoxy can conduct heat well, although it will always have less surface area to dissipate heat than the bare components. One such application of this was in the 1971 UREI 1176LN version C. Bill Putnam covered the additional "Low Noise" portion he developed for the 1176 in version C with black epoxy.[12]

Around 2000 Dumble preferred to be called by his second name Alexander. As of 2017, Dumble still built and serviced amplifiers for mainly prominent recording artists. However, if someone were to purchase a used amplifier, Dumble offered free servicing. In his older age, he only produced about five to ten amps per year. He loved to build his Ultraphonix and Rockphonix amps into Fender and Marshall chassis. The interiors are built from ground up and they are very popular with his customers. Known famous players owning either an Ultraphonix or Rockphonix Amp are Eric Clapton, Robben Ford, Peter Frampton, Kenny Wayne Shepherd, Lenny Kravitz, Chris Cobb, and Don Felder.

On May 13, 2021, guitarist Don Felder published an Instagram story with a photo of Dumble servicing his ‘65 Fender Deluxe Reverb. This was the first photo, or sighting, of Dumble in over 30 years.[citation needed] Dumble died in January 2022, at the age of 77. Robben Ford shared a video statement on his social media, and said that Dumble had been in poor health for a long time. After his passing, another recent picture of Dumble emerged of him playing the guitar, allegedly through the very first amplifier he ever built.[citation needed]

Attempted Collaborations & Proprietary Technology[edit]

Dumble had attempted multiple times to make his amplifiers more accessible. In 2013, there was an attempted collaboration between him and Fender Musical Instruments to release amplifiers with his modifications. Fender CEO Larry Thomas and CPO Richard McDonald were interacting with Dumble for several months in 2013 to create a joint Fender-Dumble product. Two Tweed Deluxe combo amplifiers were ultimately produced with his "Tweedle-Dee" modification. This collaborative idea, however, never came to fruition. In a letter of authenticity for one of the amps, McDonald stated, "[Dumble] lived 'off the grid' in the truest sense and so it was virtually impossible to create a sound, legitimate partnership."[13]

Dumble notably lived a very "off the grid" lifestyle. Friends and peers said that he had no bank account, credit card, or even a social security number. Amplifiers made by him were paid for in cash. He held his build methods and proprietary technology very close. He bared no apprentices of his amp building processes. According to Robben Ford, Dumble intended the brand to die with him.[14]

Amp models[edit]

Overdrive Special[edit]

Overdrive Special on Robben Ford's rig

The Overdrive Special is a two channel amplifier, with a clean channel and a second "overdrive" channel. This overdrive channel "cascades" from the first channel into at least one additional gain stage in the overdrive channel. This means that the clean channel tone stack and gain stages cascade into the gain stage of the overdrive channel, overdriving the clean channel. In a sense, the overdrive channel sits "on top" of the clean channel. This is Dumble's most popular model, and subsequently is the most frequently seen. That said, the Overdrive Special (ODS) varies from decade to decade, and serial number to serial number. For example, though most ODS amplifiers use 6L6 tubes in the power section (commonly associated with Fender amps), some have EL34 tubes (commonly associated with Marshall amps).

On the other hand, even the many 6L6 versions of the ODS vary considerably. For example, some have a clean channel that stays clean "all the way up to 10" (referencing a gain potentiometer ranging from 1 to 10). Others have a clean channel that starts to "break up" around 3. Some overdrive channels can only reach a minimal amount of breakup, even when dialed up. However, most ODS overdrive channels have a large amount of tube distortion available. Many later versions of the ODS have "HRM" controls on the inside of the amplifier, which is a "hot rubber monkey" tone stack that sits "on top" of the overdrive channel or, in other words, comes after the overdrive channel tube gain stage.

There are commonalities across all ODS amplifiers. Firstly, the ODS amps are known for their harmonic richness in the overdrive channel breakup, and transparent "open-ness" in the clean channel. Guitarists describe the overdrive channel using terms like sustaining, blooming, and musical—and call the clean channel "fast", "huge", and "responsive".[15] Robben Ford describes the tone of the ODS as having "a perfect sonic curve, the lows are deep and rich but not unclear, it doesn't mush out like some amps will. You have the frequencies there for your use. The mid range [is] punchy and clear and the high end, bright, clear but doesn't hurt your ears. It's loud but it sounds good."[16]

In an interview with Premier Guitar, Ford claims that Dumble told him that the original inspiration for the Overdrive Special came while watching Ford play live in the 1970s at a bar in Santa Cruz. Ford was using a mid-60s blackface Fender Bassman, and running a tube screamer in front of it to overdrive the tubes to breakup. Supposedly, Dumble liked Ford's sound, and while contemplating it had the revelations that led to the original Overdrive Special. Since buying his ODS, Ford has almost exclusively used his original Dumble or an exact clone of it in live performances.[17]

Overdrive Reverb[edit]

An Overdrive Special amplifier with an internal Reverb Circuit.

Steel String Singer[edit]

The Steel String Singer is an adjustable single channel "clean" amplifier with reverb.[citation needed]. Fewer than 12 of the original Steel String Singers have been accounted for.[citation needed]

As is typical with Dumble amplifier models, the Steel String Singer (SSS) varies from serial number to serial number. For example, The first SSS (made for Henry Kaiser) has a built-in vibrato circuit. Also, despite its reputation for a clean sound, the earlier SSS (and possibly #7) breaks up when the input gain is turned up or pushed by a strong input signal.[15] Earlier versions also had more complicated phase inversion techniques that had been pioneered in vintage high fidelity amplifiers, and Fender style transformers. Starting with #4, Dumble simplified the phase inversion and gave the amp more negative feedback, which further cleaned up the signal. These updates significantly changed the sound and feel of the circuit, and became standard to the SSS model from #4 and on. The sound the Steel String Singer is most known for is a "clean feedback" effect, in which the amplifier feeds back, even though the signal remains clean. This is most apparent in later SSS models, though a balance of factors contribute to this behavior, and earlier SSS versions and other Dumble models reportedly imitate the effect under certain conditions.

Most common features of every Steel String Singer are control oriented. Every SSS has special high and low cut filters that adjust overall tone late in the circuit. Every SSS has reverb, and every SSS has special coupling techniques and a larger chassis style. Guitarists often characterize its sound as extremely clean and compressed, with dynamic response and a lush reverb circuit. Its EQ is generally considered relatively flat internally, but malleable through the front panel controls and overall responsiveness. There are reportedly "higher highs" and "lower lows" that are not often heard through other amplifiers, and a significant amount of harmonic response to the strength of the input signal.

Notable owners and users of the Steel String Singer include: Stevie Ray Vaughan, Eric Johnson, David Lindley, Jackson Browne, John Mayer, Kirk Hammett, and Henry Kaiser.[18]


A single channel "no frills" combo amplifier, similar in appearance to the tweed Bassman. This was the most expensive amplifier on Dumble's amplifier price sheet in the 90s. Bonnie Raitt is a notable original owner of a Manzamp.[19]


One of the earliest Dumble amplifiers, this was also the model that Stevie Ray Vaughan and Double Trouble used for 80% of the guitar tracks on their debut album, Texas Flood, which was recorded at Jackson Browne's studio. Browne is a long time friend of Dumble, and owns some of his earliest amplifiers (including the first Overdrive Specials). Jackson Browne's collection of amplifiers introduced Vaughan to Dumble's amps, and Browne introduced Vaughan to Dumble so that he could buy his first Steel String Singer.


The Winterland was a 300-watt bass amplifier Dumble made in the 1970s.


Despite the variability among Dumble tonestack voicing and operation, most Dumble amplifiers have certain controls in common:

  1. Bass, Middle, and High frequency potentiometers
  2. Two voicings to choose from: Jazz, and Rock
  3. Boosts for each frequency – deep, and bright (some have mid boosts)
  4. An EQ bypass that bypasses the tonestack entirely (some models have an actual boost rather than a bypass)[11]
  5. Overall power amp Presence control, or a Contour tone cut (most have one or the other, but some have neither)


Dumbleator II

Dumble also made a tube-buffered external effects loop called a Dumbleator. A few Dumble amps have a Dumbleator circuit built in, but most have "un-buffered" input jacks that tap directly out of the pre-amp and into the power amp. Dumble likely created this external loop because of the difficulty of fitting effects loop buffering into the amplifier chassis (and the limited use of effects loops for most players). The Dumbleator has separate Send and Receive controls for the effects, and a Bright switch on at least the return. Later models also have a Bright switch on the send. Dumble also made stereo versions. This effects loop buffering is essentially a cathode follower for the send, into a gain stage for return.

Notable players[edit]

  • Eric Clapton (has used various Dumble amps and Dumble modified/refurbished Fenders over the years)[20]
  • Sonny Landreth (Overdrive Special) [21]
  • Stephen Bruton (had a low-watt Dumble with 4x10" speakers)[22]
  • Larry Carlton[23] Overdrive Special
  • Robben Ford (bought an Overdrive Special in 1983 and had a model custom-built in 1993/4)[24]
  • David Lindley (original owner of Overdrive Special #2, and Steel String Singer #3, and used them in stereo live)[25]
  • John Mayer (Steel String Singer – also has a large collection of used Dumble amplifiers)[26]
  • Lowell George had an early custom Dumble head he used for most of his career.[27]
  • Carlos Santana (has at least one Overdrive Reverb and a Steel-String Singer purchased in the early 2000s, and uses Bludotone clones of his Dumbles live besides his Mesa Boogies)[28]
  • Stevie Ray Vaughan (Steel String Singers – original owner of both #7 and #8, and had an association with #9)[29]
  • Henry Kaiser (1978 Dumble Overdrive Special, original and current owner of Steel String Singer #1, original owner of SSS #4, other ODS's as well)[30]
  • Joe Bonamassa (owns multiple Overdrive Specials, including one formally owned by Lowell George.) [31]
  • Keith Urban (Overdrive Special) [32]
  • Steve Kimock – 50-watt and 100-watt Dumble Overdrive Specials [33]
  • Ben Harper – 3 × Overdrive Specials (50w head + 2×12" Cabinet, 100/50w 1×12" Combo, 100/40w Head + matching 1×12" Cabinet)[34] In March 2016, Harper explained that Dumble had him plug his guitar directly into the oscilloscope so he could note the frequency patterns of Harper's instruments and voice Harper's Overdrive Special accordingly.[7]
  • Eric Johnson (Steel String Singer, Overdrive Special) [35]
  • Kirk Hammett (Steel String Singer) [36]
  • Jason Isbell (Dumble modified Fender Pro and Dumble Overdrive Special) [37]
  • Kenny Wayne Shepherd (Dumble modified Tweed Deluxe, nicknamed "Tweedle-Dee.")[38]
  • Jackson Browne (Original owner of Overdrive Special #1, Dumbleland, and Steel String Singer #2)[39]
  • Ry Cooder was the original owner of the Dumble Borderline Special (a 50 watts Overdrive Special with added tremolo effect). According to some sources Ry got so fed up of waiting for repairs or customizing, he put the amp head in Dumble’s driveway and drove over it with his car, destroying the amp.[40]
  • Christopher Cross recently stated in an interview with Rick Beato that he recorded a lot of hits such as “Ride like the Wind” and many others using various Dumble Overdrive Specials.[41]


  1. ^ Meeker, Ward (April 2022). "Alexander Dumble, 1944–2022". Vintage Guitar Magazine. Retrieved 29 December 2022.
  2. ^ "Dumble Amps on Instagram: "It is with great sadness that we announce the passing of Howard. His work brought joy and inspiration to countless musicians and engineers. May he Rest In Peace."". Instagram. Retrieved 2022-09-12.
  3. ^ Hunter, Dave (May 2011). "Robben Ford's '82 Dumble OD Special". Vintage Guitar. pp. 62–64.
  4. ^ Hunter, Dave (June 2011). "25 Most Valuable Amplifiers". Vintage Guitar. pp. 38–40.
  5. ^ "150 watt Dumble amp specifically made for Merle Haggard! $200,000!!! from GrooveSession – Download Facebook Videos". GenFK.com. Retrieved 28 May 2018.
  6. ^ "On March 2nd, 2017, I talked to Howard Alexander Dumble (Part 1)". 2 March 2017.
  7. ^ a b "Ben Harper's Arresting Developments". 30 March 2016. Retrieved 28 May 2018.
  8. ^ a b 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 978-0-87930-767-7. Retrieved 27 August 2012.
  9. ^ Fjestad, Zachary R.; Fjestad, S. P. (2003). Blue Book of Guitar Amplifiers. Blue Book Publications. ISBN 978-1-886768-42-0.
  10. ^ Molenda, Michael (2010). Guitar Player Presents Carlos Santana. Hal Leonard. p. 77. ISBN 978-0-87930-976-3.
  11. ^ a b Falla, Jeffrey; Johnson, Aurora (2011). How to Hot Rod Your Fender Amp: Modifying Your Amplifier for Magical Tone. Voyageur. p. 143. ISBN 978-0-7603-3847-6.
  12. ^ "1176 and LA-2A Hardware Revision History – Universal Audio". Retrieved 28 May 2018.
  13. ^ https://cartervintage.com/shop/dumble-tweedle-dee-deluxe-1x12-combo-2013-tweed/2f3b3LY0T2BHycvoWYDI0ItvlGZ
  14. ^ https://www.youtube.com/watch?v=4z-IkXE36DI
  15. ^ a b "Dumble video/sound clip reference, real Dumbles only please – Page 17 – The Amp Garage". ampgarage.com. Retrieved 28 May 2018.
  16. ^ Reverb (2017-08-24), Robben Ford on Dumble Amplifiers | Reverb Interview, retrieved 2018-01-09
  17. ^ "Rig Rundown: Robben Ford". 19 March 2014. Retrieved 28 May 2018.
  18. ^ "Dumble SSS – history and info – The Amp Garage". ampgarage.com. Retrieved 28 May 2018.
  19. ^ "Dumble amplifiers information archive – courtesy of Rob Livesey". thesubjectmatter.com. Retrieved 28 May 2018.
  20. ^ "Eric Clapton Talks Gear, Robert Johnson and New Album, 'I Still Do'". Retrieved 28 May 2018.
  21. ^ "Sonny Landreth Interview - Tones and Tuning | Guitar.com". Archived from the original on 2016-06-20. Retrieved 2017-06-13.
  22. ^ Moseley, Willie G. (May 2004). "Stephen Bruton In the Spirt of the Ft. Worth Tradition". Vintage Guitar. Retrieved 20 December 2011.
  23. ^ Heidt, John (May 2001). "Larry Carlton: The Return of Mr. 335". Vintage Guitar. Retrieved 20 December 2011.
  24. ^ Forte, Dan (August 2009). "Robben Ford". Vintage Guitar. Retrieved 20 December 2011.
  25. ^ Forte, Dan (February 2007). "David Lindley: String Theory". Vintage Guitar. Retrieved 20 December 2011.
  26. ^ Dirks, Rebecca (9 September 2010). "Rig Rundown – John Mayer". Premier Guitar. Retrieved 9 June 2014.
  27. ^ Kening, Dan (August 1976). "Lowell George of Little Feat". Guitar Player. Archived from the original on 2012-01-22.
  28. ^ Forte, Dan (April 2010). "Carlos Santana". Vintage Guitar. Retrieved 20 December 2011.
  29. ^ "Stevie Ray Vaughan Rig". Guitar Geek.com. 2010. Archived from the original on 24 September 2015. Retrieved 7 October 2013.
  30. ^ "Henry Kaiser's 5 Essential Effects". premierguitar.com. June 2013. Archived from the original on 23 September 2016. Retrieved 4 May 2014.
  31. ^ "Joe Bonamassa talks new album, Strats, Dumbles and Hendrixs". musicradar.com. August 2014. Retrieved 6 Jan 2015.[permanent dead link]
  32. ^ "Keith Urban: Guitars, Cars & The Whole Crazy Thing". Retrieved 28 May 2018.
  33. ^ http://www.online-discussion.com/SteveKimock/viewtopic.php?t=402/; http://kimock.com/kimockskorner/2014/photo-and-description-of-current-rig-on-tour/ Archived 2019-03-24 at the Wayback Machine
  34. ^ "Ben Harper and Jason Mozersky: White Lies for Dark Times". Retrieved 28 May 2018.
  35. ^ Inc., Equipboard. "Eric Johnson's Dumble Steel String Singer Amplifier". Equipboard. Retrieved 28 May 2018. {{cite web}}: |last= has generic name (help)
  36. ^ Administrator. "Metallica – Kirk Hammett's Guitar Gear Rig and Equipment". www.uberproaudio.com. Retrieved 28 May 2018.
  37. ^ "Rig Rundown: Jason Isbell & The 400 Unit". 2 December 2015. Retrieved 28 May 2018.
  38. ^ "Rig Rundown – Kenny Wayne Shepherd". 22 February 2012. Retrieved 28 May 2018.
  39. ^ "Adventures in Amplification: Lineage of a Dumble OD-100WR". Archived from the original on 22 January 2018. Retrieved 28 May 2018.
  40. ^ "Fender Stratocaster". Pinterest. Retrieved 2022-11-06.
  41. ^ "Christopher Cross: His Influences, Songs and Incredible Guitar Knowledge!". YouTube.

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