Overdrive Special '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 overdrive channel. In a sense, the overdrive channel sits "on top" of the clean channel. This is Dumble's most popular model, and consequently is the most frequently seen. That said, the Overdrive Special (ODS) varies from decade to decade, and serial number to serial number. For example, although 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. For example, 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".
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." 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 an early-60s 6G6-A Fender Bassman, and running an
Ibanez 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 a ODS, Ford has almost exclusively used his original Dumble or an exact clone of it in live performances.
Overdrive Reverb An Overdrive Reverb is an Overdrive Special amplifier with an internal Reverb Circuit.
Steel String Singer The Steel String Singer is an adjustable single channel "clean" amplifier with reverb.. Fewer than 12 of the original Steel String Singers have been accounted for. 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.
Manzamp A single channel "no frills" combo amplifier, similar in appearance to the tweed Bassman. It was the most expensive amplifier on Dumble's amplifier price sheet in the 90s.
Bonnie Raitt is a notable original owner of a Manzamp.
Dumbleland One of the earliest Dumble amplifiers, it was also the model which 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 was 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.
Winterland The Winterland was a 300-watt bass amplifier Dumble made in the 1970s.
Tonestacks Despite the variability among Dumble tonestack voicing and operation, most Dumble amplifiers have certain controls in common: • Bass, Middle, and High frequency potentiometers • Two voicings to choose from:
Jazz, and
Rock • Boosts for each frequency–deep, and bright (some have mid boosts) • An EQ bypass that bypasses the tonestack entirely (some models have an actual boost rather than a bypass) • Overall power amp
Presence control, or a
Contour tone cut (most have one or the other, but some have neither)
Dumbleator 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 control. 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 ==