What is a Sovtek 6H30,6C45, and 6C33CB?
In short, they are vacuum tubes. There are
four stages to a tube amplifier. They are: the voltage amplifier stage,
the phase splitter/invertor stage, the driver stage, and the power
stage. Without getting into too much gory detail, the 6H30 and 6C45
amazingly linear. For this amplifier, this completely eliminates the
for corrective circuitry. The result sound is accurate, simple, and
pure. The power stage requires a different type of tube, one which can
a lot of power. The 6C33CB is a relic from the US/Soviet cold war era
that is still in production. While the US was designing their military
toys with transistors, Russia could not obtain that technology. As
they continued their research and development into vacuum tubes. What
are some tubes with absolutely astounding features. The 6C33CB is one
of those tubes. Originally designed as a voltage controller for MIG
microwave circuits, this tube can withstand multiple impact loads up to
3.5g and single impact loads up to 10g. On the flip side, the 6C33CB is
a nightmare to drive because of its dynamic variations in impedance and
response characteristics. We proudly admit that the proof of concept
handles the 6C33CB most admirably. Actually, the dynamics of the
extend from 10 Hz to over 200,000 Hz.
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
amplifier because the electronics are always working their little
out; however, it produces one of the least distorted most true sounds
available. Push-Pull amplifiers use two tubes working together to get
and to cancel out certain aspects of noise that can be created by
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. Their voltage swing can be
increased, or their 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 because, in general, there are fewer components required to make
tube amplifier work well. As such, the possibility of the sound being
by a component is reduced. This keeps us in line with our original
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
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.