We carefully select all components for performance and value. We have selected components that will return the best value.

For instance, the MILLS current sensing resistors, the op amps, and the hand selected MOSFET inputs stage for power amplifiers. We don't cut corners, but at the same time, we don't waste money on "audiophile" components which offer no real advantages.

We don't cut corners

Direct Servo is a patented technology. The patent was filed in 1995. The name "Direct servo" is coined from the fact that servo signal is directly fed back to the feedback summing points of power amplifier, without going through any active devices such as operational amplifier or transistors. This feedback arrangement ensures minimal sonic degradation and therefore produces the most musical bass sound.

Direct servo also produces a bass sound that is more musical than the accelerometer-based servo subs because there are quite a few drawbacks in the latter. First, an accelerometer is just another mechanical assembly. Very often the accelerometers used in those subs are borrowed from other non-music applications. As a result, while they may produce low distortion on paper, it is not necessarily reflected into the sound qualities that audiophiles are looking for. Second, accelerometer-based subs cannot work without heavy protection circuitry around them. That adds to the circuit complexity and further degrades the sound quality. On the other hand, servo signals from Direct servo subs are derived from coils immersed in a magnetic field - one of the oldest and most proven ways of creating sound. Their simplicity of form eliminates any parasitic and secondary mechanical effects. The result is a very articulate and defined bass sound. The sensing signal is referenced to the motor frame. Therefore, no enclosure movement or vibration can induce any transient response.

For the current sensing resistor, we use non-inductive power resistors made by MILLS. They are audiophile grade and retailed for $6 each. Cheap power resistors are only fifty cents! However, the sound quality is much better with MILLS resistors. There is absolutely no reason to ruin the sound just to save $6. Similarly, we use a MOSFET front end in the power amp to produce a smoother and somewhat sweeter mid bass sound. By contrast, the sound from a bipolar front end is grittier. In terms of op-amp selection, we use a combination of OPA2134 and TL072. These op-amps are used in many high end preamplifiers, so it is not surprising that they perform very well at preserving resolution and detail in our amplifiers.

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