Mesa/Boogie Vacuum Tube Audio owner manual On TRIODES, Pentodes & Irishmen, Class a Operation

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5 - 5 CLASS A OPERATION: ( Continued )

amplification was going on in the opposite half circuit. That’s the Class B part.

The trick is to get the large magnitude signal to pass back and forth in a push-pull circuit without major distortion occurring due to cut- off. That’s because the tubes, having first been driven into cut-off, must then resume drawing current. That off and on action no longer reflects voltage changes at the grid (musical signal) and thus distortion occurs.

By contrast, Class A operation comprises merely increases and decreases of current flow, but current cut-off is avoided. Grid voltage and plate current maintain a simple linear relationship without exceeding the tube’s preferred operational boundaries. You could call Class A the sweet spot of tube amplification characteristics.

The TIGRIS is both push-pull and Class A. This means that while the signal is divided into two complementary halves for increased power, some current continues to flow in both halves at all times. There is no point at which a normal signal voltage causes cut-off and thus the distortion products which accompany Class B are avoided.

Notice that word, normal. It would be possible to drive the TIGRIS into cut-off by turning it up too loud, but by then saturation and its obvious distortion would already be occurring. Thus the signal condition would be abnormal.

In the TIGRIS, the onset of saturation and cut-off occur almost simultaneously in the all Pentode position thus maximizing the available power under Class A conditions. In power settings utilizing partial Triode performance, saturation occurs well before cut-off and, as noted, output power is also reduced. In other words, saturation occurs in the positively driven half of the signal well before cut- off occurs in the negatively driven half.

If Class A is superior, then why aren’t all amplifiers operated that way? Because the need for high idle current causes more power to be wasted as heat than is provided for doing useful work.

Is that why the Class A TIGRIS is modestly powered while its big sibling, the BARON, runs Class AB? Yes. However, the BARON is so powerful that it almost never shifts out of the Class A portion of AB operation - at least not until shattering volumes of Pentode power have been attained.

There’s also an added sonic advantage to lower power amplification and that is that smaller output transformers tend to sound sweeter and more open. Physically larger output transformers exhibit increases in both distributed capacitance and stray inductance which tend to roll-off and phase-shift extreme high frequencies. Also, to provide full power down into the lowest frequencies requires large transformers with very high iron flux capability - a dilemma discussed further in the BARON Owner’s manual. Basically, smaller is better - until low end performance audibly suffers.

Nevertheless, we expect you’ll be pleasantly surprised - if not somewhat shocked - by what a muscular punch your new TIGRIS packs. Wimpy it is NOT! In Full Pentode mode with moderate feedback, you can expect to Rock the House with tight, well-defined, powerful sounding response! Check your lease before seeing just how loud the TIGRIS can play! Not that we advocate high listening levels, but listening to music is supposed to be fun, and sometimes that equates high volumes.

Chapter 6 - ON TRIODES, PENTODES & IRISHMEN:

With apologies to Friends and Relatives from the Emerald Isle - who will make their appearance soon enough - the humor which follows is dedicated to the memories of Spec McAuliff and Fae (Rafael) McNally, two of the True Greats.

As their numerical references suggest, the terms Diode, Triode and Pentode indicate the number of elements within the vacuum tube i.e. two, three or five. All tubes also require a filament or heater which is not included in the count. Its purpose is to excite electrons from the cathode coating by raising the temperature such that they are able to boil out of the electron-rich coating material and form a cloud of free electrons in the vacuum space surrounding the cathode.

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Contents Vacuum Tube Audio Page Table of Contents Chapters Precautions USE Common Sense and Always Observe These PrecautionsOperating Instructions OverviewFront View Tigris Location InstallationUnpacking Speaker Binding PostsSpeaker Binding Posts HOOK-UP OptionsHOOK-UP Options HOOK-UP Options Detachable Power Cord A.C. on / OFF SwitchWarm / Operate Switches Ground Switch CongratulationsCongratulations Advanced FeaturesAbout BREAK-IN Tandem State ImagingTandem State Imaging Power Tube Blend Headphone OutputHeadphone Output Auto BiasCathode resistor Class a OperationOn TRIODES, Pentodes & Irishmen Class a OperationOn TRIODES, Pentodes & Irishmen Triodes Tube Maintenance & Tube Rolling Tube MaintenancePentodes Tube Maintenance Evolution of the TigrisTube Rolling Evolution of the Tigris Customer Service Mesa/Boogie Professional HeritageTrouble Shooting Specs Versus PerformanceBasic Specs Specs Versus PerformanceWarranty 14 1 Within the US14 2 Outside the US Warranty Registration Form From Mesa Boogie Spirit of Art in Technology

Vacuum Tube Audio specifications

Mesa/Boogie is a revered name in the world of vacuum tube audio, renowned for its high-quality amplifiers that have shaped the sound of modern music. Founded in 1969 by Randy Smith in California, Mesa/Boogie began by transforming Fender amplifiers into customized, high-gain models, ultimately gaining a reputation for producing powerful, versatile, and low-noise amplifiers. The signature sound of Mesa/Boogie is characterized by a complex harmonic richness, warmth, and clarity that resonates with guitarists and audiophiles alike.

One of the standout features of Mesa/Boogie amplifiers is their all-tube design. Utilizing vacuum tubes as the primary amplification source, these amps deliver a dynamic range and tonal complexity that solid-state amplifiers struggle to match. The quality of the tubes used, often hand-picked or specifically designed by Mesa, contributes to the unique audio characteristics of each model. The use of EL34, 6L6, and 12AX7 tubes in various configurations allows for a range of tonal options, from lush cleans to searing leads.

Mesa/Boogie amplifiers are also distinguished by their innovative technologies. The brand pioneered the dual rectifier system, which allows players to switch between tube and solid-state rectification. This feature gives musicians the ability to tailor their sound to preference, enhancing the responsiveness and feel of the amplifier. The Contour controls found on many models further exemplify Mesa’s commitment to versatility, allowing for fine-tuning of EQ settings that adapt to different musical styles.

Another hallmark of Mesa/Boogie designs is their attention to build quality. Each amplifier is crafted with robust materials, ensuring durability and reliability even in demanding performance environments. The custom cabinets and speaker selections are optimized to complement the amplified tone, providing a cohesive sound that resonates in live settings.

Mesa/Boogie’s reputation is enhanced by their extensive lineup, including the Mark series, the Rectifier series, and the Lone Star series. Each line caters to different playing preferences and styles, from jazz to metal. The versatility of these amplifiers makes them suitable for diverse genres, allowing musicians to explore their sonic identities.

In conclusion, Mesa/Boogie remains a leading force in vacuum tube audio, combining traditional craftsmanship with cutting-edge technology. Their dedication to quality, innovation, and tonal versatility ensures that they remain a favorite among guitarists seeking the ultimate sound experience. Whether in the studio or on stage, Mesa/Boogie amplifiers continue to inspire musicians to push the boundaries of creativity.
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