Dr. Boogey Emulation of the Mesa Boogie Dual Rectifier Solo Head

| December 26, 2010 | 0 Comments

The “Doctor Boogey,” also sometimes referred to as the Dr. Boogey or Dr. Boogie, is a do-it-yourself circuit emulation of the Mesa Boogie Dual Rectifier Solo Head amplifier. It was designed by Chris Ntaifotis who goes by the handle “electrictabs” in various DIY forums. In this article we’ll cover how you can create your own kit for this pedal. But first let’s take a look at the amplifier being emulated.

Mesa was started by Randall Smith as a shop which repaired and modified Fender amplifiers. Smith’s breakthrough in tone came when he modified an amplifier by adding an extra gain stage to a preamplifier, resulting in three variable-gain controls at different points in the circuit. The high-gain amplifier that resulted attracted some prominent guitar players, including Carlos Santana and Keith Richards, as early customers. Under the name MESA Engineering, Smith’s reputation grew and he set about designing a new guitar amplifier around the high-gain principle, resulting in the Mesa/Boogie Mark I. This first amplifier grew into a large line of amplifiers now made by Mesa/Boogie.

MESA/BOOGIE DUAL RECTIFIER SOLO HEAD

Today the Rectifier series is Mesa’s flagship line of amplifiers. The Dual Rectifier series of amps have two forms of electrical rectification (conversion of power from AC to DC): silicon diodes and one or more vacuum tubes that the user could select via a switch located on the back panel of the amplifier. This first appeared in the Dual Rectifier Solo Head and is part of the magic behind the whole Dual Rectifier series of amplifiers. The patented switchable feature allows you to select between two different types of rectifiers for different sounds and feel:

  • Silicon Diode Rectification (Hi Power) offers more punch with a tighter attack, added brightness and substantially more headroom. This would be the preferred position for loud clean playing or tight rhythmic playing with a high front-end Volume setting.
  • Vacuum Tube Rectification (Normal) pays tribute to the vintage amps of yesteryear when only tube rectifiers were available. The Vacuum Tube position (two 5U4G rectifier tubes) shines for single note lead work and delivers a warm, breathing clean sound in the Rhythm channel. Most players end up leaving their Dual Rectifier Solo set to the Vacuum Tube position all the time.

The Dual Rectifier’s audio signal chain is equipped with five 12AX7 preamp tubes and a quartet of 6L6 power tubes, producing 70-100 watts. As in most guitar amplifiers and especially in all-tube circuits, the Dual Rectifier Solo’s Gain control is the most powerful control in the preamp. It shapes the overall style and character of the sound and is responsible for whether the sound is clean, overdriven or anywhere in between. It not only determines the amount of drive, but also acts as an integral part of the tone control string as well. By itself the GAIN Control has basically three tonal regions:

  • Low – provides the cleanest, least saturated sounds and in this region the sound will be brighter and contain more upper harmonics lending a three dimensional character to the sound.
  • Middle – enhances the saturation and replaces some of the upper harmonics with a richer, warmer quality and a fuller bottom end response. Not yet fully saturated, this region contains many of the Dual Rectifier Solo’s best sounds…especially for soloing due to the crucial blend of an expressive attack combined with ample sustain.
  • High – saturates the signal and enhances low and low-mid frequencies. While this region provides the maximum saturation and therefore sustain, if also compresses and softens the attack characteristics.

Now that you have some idea of the history and principles behind this amp, let’s give a listen to a demonstration video to hear what it is the Dr. Boogey will try to emulate:

DOCTOR BOOGEY EMULATION PEDAL

The Doctor Boogey circuit design uses junction-gate field effect transistors (JFETs) instead of the vacuum tubes used in the Dual Rectifier amplifier. A JFET can be thought of as similar to a vacuum tube in that it is a voltage-controlled current sink. The Dr. Boogey design has five stages of JFET gain, with gain and tone controls, resulting in an ultra-high gain distortion pedal. The design is meant to emulate the combined characteristics of the Dual Rectifier’s orange and red channels. Let’s listen now to a demonstration video of the Doctor Boogey pedal:

There is no ready-made kit available for this pedal so if you want to build one you’ll need to create your own kit. The schematic, printed-circuit board design and parts-list are all available at the gaussmarkov site. When choosing the enclosure, be sure to allow adequate room for the six external potentiometers that are in the design. Here’s a video showing the steps of building this pedal:

If you decide to build this pedal you may want to review the comments and refinements discussed in the Doctor Boogey thread at DIYstompboxes.com.

Category: Pedal & Effects

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