Driver Tubes, Tubes VS. Transistors | Mesa/Boogie 400 manual

DRIVER TUBES

The four small tubes are all type 12AX7, also known as 7025, ECC83 or MESA SPAX7. These tubes are very long lasting and trouble free in the Strategy, but best performance will result from using genuine replacements. The input stage of your 400 uses a special "instrumentation grade" differential amplifier with a proprietary constant-current-source diode.

This is a high-tech little solid-state part which enables the phase splitter to work in a simple, self-balancing mode -- one of the keys to great performance. Occasionally a certain 12AX7 will not quite match this device and one channel will sound weak as a result. Merely try another tube, or exchange it with the one next to it. Generally though, our experience with the M-180 and M-190 predecessors of your Strategy 400 means that you should enjoy many years of trouble-free service from your Strategy 400 Stereo. Following is a brief discussion of the differences between tubes and solid-state, however we think the performance of your new Strategy 400 will be the strongest argument of all in favor of great tube amplifiers.

TUBES VS. TRANSISTORS

Much has been written on this topic... It's an interesting one and will never be fully decided one way of the other. Because of the great economic advantage of solid-state, audio has proliferated beyond any prediction that could have been made a mere 25 years ago. Cassette decks, ghetto-blasters, home recording, pocket radios -- all these would be too big and expensive to build in mass quantities with tubes. Yet most musicians agree that tube amplifiers (and many of you have purchased your Strategy just for use in your own rack, where it's totally state-of-the-art). Less well known - but equally convincing - is how well the Strat delivers for bass, keyboard or stereo playback. You've got to hear it to believe it; then the arguments for the economic benefit of solid-state can be judged against the better sonic performance of tubes.

The basic characteristic of a transistor is that it operates much like a simple switch -- going either full-on or full-off. That's why they're so good in computers and other digital applications. A tube, on the other hand, is basically an analog device: It's "full-on and full-off" switching operations are a bit hazy and strained because it would rather work the in- between area of "partially-on", tracking a "now-more, now-less" type signal. Think of a tube behaving like its British name: a valve, regulating a flow of current that is dynamic and pulsing. Then think of the physical action of live music: it's a series of pressure changes in the air which act on the ear drum in the manner of a pulsing and dynamic flow (analog behavior) as opposed to a digital sequence of "full-pressure-or-no-pressure". So the basic nature of a tube's operation makes it the more natural choice for musical amplification. Yet solid-state amplifiers usually outperform their tube counterparts when it comes to producing great specs in the laboratory. Here's an explanation of why this is and why it doesn't matter.

DISTORTION AND NEGATIVE FEEDBACK

Negative Feedback is a correcting process used in virtually all amplifiers to "erase" distortion. It works by taking a portion of the output signal (traditionally right from the speaker jack) and re-inserting it into the input -- but out-of-phase with the original signal. By definition, anything extra produced by the amplifier is distortion. So by inverting a portion of the output signal and running it back through the amp "upside down", the distortion products

400 specifications

The Mesa/Boogie 400 is an iconic bass amplifier that has set the standard for power, versatility, and tonal quality in the world of professional music. Renowned for its robust construction and cutting-edge features, this amplifier is designed to meet the demands of both studio and live performances, making it a favorite among musicians.

One of the main features of the Mesa/Boogie 400 is its high wattage output, providing a staggering 400 watts of power. This ensures that even in the most demanding performance venues, the amplifier delivers a punchy and clear sound that can easily fill the space. The power handling capability enables it to drive various speaker configurations, making it adaptable to different setups.

At the heart of the Mesa/Boogie 400 is a sophisticated preamp design that utilizes a hybrid of tube and solid-state technologies. This combination allows for a warm, rich tonal character provided by the tubes, while maintaining the reliability and clarity that solid-state components offer. The amp typically features a dual-channel preamp, allowing players to switch between different tonal profiles or blend them for a more complex sound.

Another significant characteristic of the Mesa/Boogie 400 is its extensive EQ section. With multiple bands of EQ, musicians can sculpt their sound precisely to their liking, enhancing the low-end thump, mid-range clarity, and high-end presence. This level of control enables bassists to tailor their tone to fit various genres, from rock to jazz and beyond.

The amplifier is known for its durability, constructed with high-quality materials that withstand the rigors of touring. Its rugged chassis and reliable components ensure that it delivers consistent performance through years of use. Additionally, many models of the Mesa/Boogie 400 incorporate advanced cooling systems to prevent overheating and maintain optimal operation during prolonged gigging sessions.

Portability is another feature that cannot be overlooked. The Mesa/Boogie 400 often comes in a lightweight package relative to its power output, allowing musicians to transport it easily to rehearsals and performances.

In summary, the Mesa/Boogie 400 represents a pinnacle of bass amplification, known for its power, tonal flexibility, and durability. With its hybrid technology, comprehensive EQ options, and road-ready design, it delivers exceptional performance for serious bassists looking to elevate their sound.