Aclam Guitars

Dr Robert V2

Name: Dr Robert V2
Brand: Aclam Guitars
Price: 329.6 USD
Availability: InStock

$329.60 USD

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Dimensions

Length 5.4"
Width 3.4"
Height 2.2"

Specifications

9V DC Center Negative or
9V Battery
35ma

Product variants

VOX UL730) "BEATLES" Revolver & Sgt. Pepper

THE MOST ACCURATE REPLICA OF THE ORIGINAL UL730 PREAMP

Sometimes you can’t trust the internet or an old schematic! We’ve found major discrepancies between the published schematic and the real thing, such as component types and values, so we can assure this is the closest you can get to the rarest Vox amp! Following the preamp there’s a custom FET based circuit emulating the saturation produced by the UL730 EL84’s tube power amp section. Additionally, the circuit works with the same voltages found on the original amp thanks to a charge pump circuit which takes the 9VDC from the battery or DC plug and converts it to 18VDC.

(Although based on the UL730 preamp, the UL400 series (designed for bass) shared almost the same circuitry.)

The Vox® UL700 amp series were the secret weapon used by The Beatles to achieve the unique guitar tone on Revolver and part of Sgt. Peppers. They were also used by The Rolling Stones, Joy Division and Jimmy Page of Led Zeppelin

Introduced in 1966 these state-of-the-art guitar amps mixed a solid-state preamp with a tube power amp section.

Tubes were standard at that time but had the inconvenience of being voluminous and prone to fail, plus they needed bigger transformers due to impedance matching and power requirements. Transistors were the solution as they were way smaller, reliable and took much less energy to operate. So, in 1965, Vox engineer Dick Denney decided to develop a hybrid amp with a solid-state preamp and tube powered amp section.

Thanks to the relatively new transistor technology, lots of features could be added. Top of the line models included two channels with three band eq each, distortion, tremolo and reverb.

There were many variants with different power ratings, but the ones used by The Beatles were the UL730 (30w) and UL7120 (120w).

Unfortunately, aside from The Beatles, those amps weren't popularly used at the time and most of them ended being returned to Vox for their disposal.

Only a small number of UL730 units survived (around 20/30 units as some renown Vox connoisseurs state), attaining the title of being the most collectable Vox amps, with prohibitively collector pricing.

Now they are the missing link between tube and solidstate amps.

The Dr. Robert is based on the Normal channel of our Vox® UL730 S/N: 3042. We traced the original tag board circuits and measured each component’s value to make the closest replica of the amp’s soul and character.

One of the keys of its tone is the “Mids” control which is one of the most interesting mid-range eq ever found on an amp. By turning it counterclockwise, a great amount of mid-frequencies will be subtracted creating a scooped sound. On the other hand, when it's turned clockwise it will bring out all the mids and the signal will build up in gain. By tailoring the “Mids” knob you can control both midrange and saturation.

As the solid-state preamp of the UL730 doesn’t create much distortion by itself we’ve coupled it with a custom FET saturation engine to mimic the attributes of the tube power amp section. Not happy with that, we’ve gone even further creating the “Mach Schau!” section, which adds saturation to your main sound and includes an independent volume control to allow you to have both a rhythmic and a solo tone.

Pedal Secrets

BASS

Sets the amount of low frequency content reaching the FET section. The Treble and Bass controls work together in a tone-stacked manner, so they are a bit interactive.

TREBLE

Controls the amount of high frequency content of the signal before reaching the FET section. Setting this knob will have an effect over the overall gain.

MACH SCHAU! GAIN TRIM

Aclam Guitars has included a Gain trim for the Mach Schau! section. This will allow you to lower the saturation and make it a little bit less aggressive. At high gain settings it’s less effective but a lower gain it will make the Mach Schau! sound a bit gentler. Try it and experiment!

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