US Amps AX - Manual (Page 17)

16
Why Tubes?
You may know that a transistor is a
modern, efficient, less expensive version of
a vacuum tube, which is the device that made
sound recording and reproduction possible in the
first place. Now, the electronics industry has been
trying for many years to equal the sound quality available from tubes. They have
been able to make transistor amps louder, cooler, more abusable, and less expen-
sive than tubes, but to this day, they’ve been unable to make any solid state amp
sound as good as a tube amp.
So, our engineer got to wondering, “What if I combined the sonic character of a
vacuum tube with the drive capabilities of solid state?”
Well, the result is the U.S.Amps’ VTCSD hybrid amps. Using the signal path
directly out of the tubes as a “steering” signal and the following drive signal wave
from the transistors as the “motor,” with absolutely no negative feedback as a
corrective to the transistor’s waveform, we achieved the most detailed, pleasing,
articulated sound available in mobile audio today.
Positive Current Sync
Negative Current Sync
Input signal is fed
DIRECTLY into the tube.
There are no solid state
gain stages or processors
in the signal path.
Direct Input
Vacuum Tube Current Sync Drive
The original high voltage tube signal is joined by
a null-gain current following circuit that is pulled
to the voltage rails by an opposing pair of
current syncs, providing a sort of amplifier
“power steering” to deliver speaker-driving
power without taxing the character of the
original tube voltage content.
fed into Output
Transformer
Yet lacks much of
the tubes’ original
dynamic range
The resultant signal
is soothing and
pleasing
Output
Transformer
converts
Voltage
Energy
into
Current
High Voltage/Low Current
Signal from Output Tube is
Low Voltage
Low Current
Tube Input
Classic Vacuum Tube Amps w/Output Transformer
Smooth, Low
Tube Voltage Negative Feedback
Transistor Switching
Noise
Listening Fatigue
Compression
and Coloration
Solid State Amplifier
Uneven Clipping
Odd-order Harmonics
Preamp Signal
Low Voltage
Low Current
Solid State Input
Hybrid Tube/Transistor Amps
Tube In, Tube Out
(Vacuum Tube Current Sync Drive)
VTCSD