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What is a Sovtek 6H30,6C45, and a KR Audio T-100?

In short, they are vacuum tubes. There are three stages to Opus 2. They are: the voltage amplifier, the driver, and the power stage. The 6H30 and 6C45 tubes are very linear. For Opus 2, this eliminates the need for corrective circuitry. The result is accurate, simple, and pure sound. The power stage requires a different type of tube, one which can handle a lot of power. The T-100 is brain child of Dr Kron, founder of KR Audio in Czech Republic. Sadly, he did not live long enough to see this tube to fruition. Since his passing, his wife (also Dr. Kron) has taken over the business and continued the tradition. The T-100 is unique in many ways . It is built with Pyrex glass and the insides are completely hand assembled and tested in very small batches. The KR Audio lead engineer, Mr. Marek Gencev does "engineering control" to ensure consistency. This means that each T-100 is essentially matched to every other T-100. These tubes have an life span of almost 10000 hours and are only available from KR-Audio.

What are Class A and Push-Pull?

Class A and Push-Pull describe the architecture of the amplifier. A class A amplifier is the least efficient amplifier because the electronics are always working their little hearts out; however, it produces one of the least distorted most true sounds available. Push-Pull amplifiers use two tubes working together to get more power and to cancel out certain aspects of noise that can be created by the electronics. A Push-Pull amplifier works alot like a slinky. The transformer is energized by two tubes operating exactly out of phase. Courtesy of the T-100 and our special toroid transformers, the Opus 2 has a power bandwidth that extends from 17Hz to over 124000Hz.

Why tubes? Why Transistors?

These questions are enough to make the hair stand up on the back of any audiophile's neck! It is a debate that continues on with a theological zeal. Technically, there are only two ways to amplify signals. Voltage swing can be increased or Current swing can be increased. There is a mechanical analogy. When you run water through the kitchen sink and shut it off quickly, the pipes bang with the inertia of the water passing through them. The force of the water is dramatically changed through this process. This is much like current flowing through a wire. Voltage swing is like having the same water in the pipe, but having a balloon at one end and a piston at the other. Very little movement of the water will make large size changes in the balloon. Tubes work like the piston and the balloon. Transistors work like the kitchen sink. In truth, each has their strengths and weaknesses. We opted for tubes because, in general, there are fewer components required to make a tube amplifier work well. As such, the possibility of the sound being altered by a component is reduced. This keeps us in line with our original goals of simplicity and purity of sound.

What is Negative Feedback?

Negative feeback is a method of circulating a small piece of the output signal back through the circuitry to gain better control of the natural hysteresis of the output transformer. Negative feedback can also be used to flatten the frequency response of a given circuit.
 The reality is that it can slow the response of the amplifier and dull the sound of the finished product.
  We are proud to print that the Opus 2 requires no feedback of any kind to alter the signal.

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