First, for the best long term reliability, tubes should be mounted in the upright position. Any other position (upside down or lateral) relies on compromise, be it restraint devices that rattle or come off, adverse thermal environments or the potential for tube damage (misalignment of the tubes’ internal elements). Studies performed by major tube manufacturers have indeed shown that tubes will function correctly and have good reliability in these other positions. However, they were not considering the typical conditions of use and abuse peculiarly common to MI amplifiers.

   Second, vibrational and mechanical shock isolation are virtually impossible to optimize in a combo type design. Optimum vacuum tube function and reliability depends on maintaining extraordinarily tight specifications in regard to the internal spacing and structural integrity of the heater, cathode, plate and various grid elements. When a tube is at operating temperature, these internal elements are in their most physically fragile condition. Continued vibrations, compounded by the very close proximity and direct coupling of the speaker can alter the position of these elements, resulting in premature failure or poor operating characteristics.

   An argument exists describing a synergistic vibrational interaction between the speaker/enclosure and the tubes/electronics. This phenomenon can be similar to the intentional generation of controlled feedback, in which the guitar resonance is excited through the air by the speaker output. Controlled feedback is one of the unique sonic attributes of the electric guitar and can be used to convey a wide range of emotion, enhancing the performance and widening the instrument's compositional vocabulary. Regarding tube and electronic component vibration, our research indicates this effect to be essentially uncontrollable and prone to degenerate into squeals and noise, rather than maintaining a harmonic relationship to the fretted note. It seems to be random in occurrence, sporadic in nature and many times atonal, modulated noise. As such, we believe improved vibrational isolation of the electronics to be beneficial to the overall tone.

   A third consideration is the tradeoff between convenience and versatility. It can be handy to carry a single (though sometimes quite heavy) amplifier/speaker combination, but differing performance and recording situations can benefit greatly by providing the most appropriate speaker configuration for the situation. The speaker type, quantity, location and enclosure design can have great sonic contributions to overall tone. We discuss this in more detail on our speaker page, but suffice it to say for now that we feel this to be the more beneficial and most versatile arrangement.

   An additional thought is that the combo arrangement typically limits the speaker enclosure design to a predominantly open back (infinite baffle) configuration. Open back enclosures can certainly sound good and perform well, depending on the specific design and driver choice. We prefer our amplifiers to have the flexibility to be used in any configuration, rather than limiting them to any specific one.

   Based on these issues, all of our musical instrument amplification products are manufactured in the head configuration. We have designed a common chassis that will allow for many of our amplifiers to be mounted in either a standard type wood enclosure or in a rack mountable configuration. Our rack mount versions will be a bit larger in RU height to accommodate the upright position of all tubes, and due to the 17" width limitation, some of our products may not be available in this configuration.

   Please click on the above tabs for specific information on each of our MI products.