What are a 6H30PI, 6C45, and a T-100?
They are vacuum tubes. The 6H30 and
the 6C45 are small signal triodes built by Sovtek for voltage
amplification. The T-100
is designed and
built for audio use by KR Audio in the heart of Bohemia, Prague.
The T-100 is the
master work of the late tube wizard Dr Riccardo Kron, founder of
KR Audio in Czech Republic. It is similar to an 845 in many
aspects, but is dramatically improved for audio quality. Sadly,
he did not live
long enough to see an amplifier ever built with this tube.
Luckily, his wife
(also Dr. Kron) has taken over the business and continued the
tradition with an incredible passion.
The T-100 is undoubtedly one of the finest low frequency audio
tubes ever built. Like all KR Tubes, it is built with Pyrex glass and
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 KR tube is precisely matched to specifications.
These tubes have an lifespan of 10000 hours.
What are Class A, Single Ended, and Push Pull?
Class A and Single
Ended/Push Pull describe
the architecture of the amplifier. Class A amplifiers are the least
efficient because the electronics are always working their little
out. Class A amps produce the least distorted most true sounds
available. Single ended amplifiers use tubes to drive the
transformer. Most electronics produce sound in a single ended
mode (on the RCA output jack). This is a perfect input for a
single ended amplifier. For an example of single ended
amplifiers, go to www.kraudio.us
Push-Pull amplifiers work like a slinky. The
transformer is energized by two tubes operating exactly out of phase.
To minimize componentry, push-pull amplifiers frequently synthetically
generate the out of phase signal, with additional circuitry. In
the case of Opus, it uses balanced
inputs directly from the equipment. While a less common signal format,
it is the least distorted push pull architecture available.
Courtesy of the
extreme care in materials and workmanship, the Renaissance Audio Opus 2
has a power bandwidth that
extends from 20Hz to over 100000Hz.
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
analogy. When you run water through the kitchen sink and shut it off
the pipes bang with the inertia of the water passing through them. The
of the water is dramatically changed through this process. This is much
like current flowing through a wire. Voltage swing is like having the
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 in the output stages because, in general, there are significantly
fewer components required to make
tube amplifier work well. As such, the possibility of the sound being
by a component is reduced.
What is Negative Feedback?
Negative feeback is a method
of circulating a small piece of the output signal back through the
to gain better control of the natural hysteresis of the output
Negative feedback can also be used to flatten the frequency response of
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 due to our extensive materials selection and
engineering development process, Opus 2 requires no
feedback of any
kind to alter the signal.