Aclam Dr. Robert

The Aclam Dr. Robert is an analog preamp and overdrive pedal that recreates the Normal channel of the Vox UL730, a 30-watt hybrid amp the Beatles used on the Revolver and Sgt. Pepper's albums¹²³. Aclam, a pedal builder based in Barcelona, owns one of the few surviving original UL730s, serial number 3042, and traced the pedal's circuit directly from that amp¹⁴. The company describes the result as "a perfect preamp and distortion tool to plug directly to the desk or into an amp"¹.

The circuit follows the UL730's solid-state preamp with a custom FET-based saturation stage that emulates the EL84 tube power amp section, so the pedal copies both halves of the hybrid design¹. On That Pedal Show, the presenters explained that Aclam added the FET section "to simulate the power valves overdriving because the preamp was pretty clean"⁵. A charge pump converts the 9V DC input to 18V DC internally, so the circuit runs at the same voltages as the original amp⁶⁷.

A Vox UL730 preamp in a pedal

The Vox UL730 was designed by Vox engineer Dick Denney in 1965 as a hybrid amp: a solid-state preamp feeding a tube power section⁷. Guitar World's Trevor Curwen notes the pedal emulates "the 30-watt version as opposed to the more p[owerful]" UL models, and that the Dr. Robert is based on the Normal channel of that amp³. Aclam developed the pedal by studying its own original UL730, serial number 3042; company co-founder Marcel Cavallé recalls "working with my pal Marc Sospedra at our workshop, studying the UL730 and playing Beatles ri[ffs]"¹¹¹.

The pedal sits in Aclam's series of Beatles-inspired amp-in-a-box pedals, alongside the Aclam Woman Tone and the Go Rocky Go White Album Edition, which recreates the solid-state Vox Conqueror¹². MusicRadar has called the Dr. Robert "the Revolver pedal"¹².

The controls

The V3 carries the same control set as earlier versions, with the Bass and Treble EQ and the Mach Schau! Gain moved from internal trimmers to external knobs¹¹³.

Guitar World's reviewer found the Mids control especially powerful: it "has a really strong influence on the saturation of the sound," cleaning up as midrange is scooped and adding saturation as mids come up³. On earlier versions he described the internal treble and bass adjustments as "a pair of 'set 'em and forget 'em' internal trimmers because it's the midrange that [matters]"³.

The Mach Schau! boost and Lo/Hi Gain modes

The Mach Schau! footswitch (named for a phrase from the Beatles' film "A Hard Day's Night") adds an extra gain stage for solos and heavier parts. Aclam is clear that it is not an independent overdrive: it is an extra tone of the main circuit, and its saturation depends on your Gain and Mids settings¹⁰. On the V3, with MS Gain set all the way down, the section "adds only a barely noticeable amount of saturation, letting you use Mach Schau!" as a clean volume boost¹.

The V3 also adds a global Lo/Hi Gain mode, toggled by pressing both footswitches together while the pedal is on¹:

• Lo Gain: the default when the pedal ships, with LEDs lit white; a slightly tamer gain structure aimed at cleaner or edge-of-breakup tones¹
• Hi Gain: retains the gain structure of previous versions, with the LEDs turning orange¹

Power: 9V center negative

The V3 is powered by a 9V DC center-negative supply with the standard Boss type 2.1mm connector, drawing a minimum of 50mA, and Aclam states it must not be powered above 9VDC¹. Earlier versions specified 9V DC center negative at 100mA minimum or a 9V battery, installed by unscrewing the baseplate⁶¹⁰⁷. Guitar World's review lists "9V battery or 9V DC adaptor, 35mA"³.

History: from the Beatles-era UL730 to V3

The Dr. Robert traces back to the Vox UL730, a hybrid amp whose design Vox engineer Dick Denney developed in 1965, pairing a solid-state preamp with a tube power amp section⁸⁷. The Beatles used the UL730 on the Revolver and Sgt. Pepper's albums⁴, and Aclam developed the pedal with Marc Sospedra at the Aclam workshop, studying the UL730 and playing Beatles riffs¹⁵¹¹. MusicRadar described the resulting pedal as "a perfect replica" of the Vox UL730².

In late 2025, Aclam upgraded the pedal to V3, adding the external Bass/Treble EQ and Mach Schau! Gain controls plus the Lo/Hi Gain mode; earlier units from serial number 1000 onward had carried an internal Mach Schau! gain trimmer¹. Pedal of the Day's review of the V3 lists the new features as "New LO/HI Gain Modes" and the "Same 3 Band Equalizer, now with external Treble and Bass controls," alongside high-end components¹³.

Limited editions: Gold Edition and Unknown Pleasures

Aclam has issued two limited editions of the Dr. Robert¹⁰⁷:

• Gold Edition LTD (reference AP0020-3): the same UL730 Normal channel circuit in a gold finish, with a charge pump raising the internal voltage to 18VDC from the 9VDC input⁷.
• Unknown Pleasures Ltd. Edition (reference AP0020-8): a version with artwork adapted from Peter Saville's design for Joy Division's debut album. Its Disorder! section has its own volume control and an internal gain trim (factory set to maximum), and its manual includes setting examples for Joy Division songs such as Shadowplay and She's Lost Control alongside Beatles tracks like Paperback Writer and Taxman¹⁰¹⁴.

Both editions share the standard pedal's dimensions, weight, true bypass switching and component list, which includes carbon comp resistors, Nichicon Fine Gold and Wima capacitors, and Alpha pots and switches⁶¹⁰⁷.

What reviewers said

One published review summed the pedal up as "a versatile drive pedal with visceral power and a raw grind that will find a role in many kinds of music," also noting the "cool graphics"³. Another reviewer wrote that "to my ear, it sounds pretty close and it'll be interesting to see what players make of it"¹⁶. Of the V3, a reviewer wrote that the Dr. Robert V3 VOX UL730 Replica "brings a very specific and unique sound to your practice room, rehearsal space or gi"¹³.

On That Pedal Show, the presenters demoed the pedal and were blunt about its appeal beyond its backstory⁵:

They also walked through the three internal trimmers on the original version: two adjustable for bass and treble, and one for the balance of the extra FET section that Aclam asks users not to touch⁵.

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