Whammerdyne Truth, Руководство пользователя

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The unique input autotransformer (Level Control) is a constant-power attenuator at all settings,
transforming voltage and current, in the same way the transmission in a car changes RPM’s and
speed.
By contrast, conventional resistive attenuators (Level Control), whether a potentiometer or a
ladder of discrete resistors, cut down on the power of the signal as the volume is lowered. With
a resistive attenuator, the grid of the input tube sees a low source impedance at full volume, 1/2
the rated value at -6 dB, and gradually less as the volume is lowered. From the perspective of the
input tube grid, the source impedance is both high and variable, depending on volume setting.
This changes the bandwidth of the input tube, and in subjective terms, can affect the sense of
dynamics.
The autoformer of the Truth
™
amplifier presents a low source impedance to the 6DJ8 grid at
full volume, and then goes even lower as the volume is lowered. For example, if the source
component has an output impedance of 100 Ohms, at the -6dB attenuation setting, the grid of
the input tube sees a source impedance of 25 Ohms; and it goes down from there. A 100 K Ohm
resistive attenuator presents a source impedance of 25K Ohms to the grid of the input tube if the
pot is set to - 6dB.
At every volume setting of the Truth
™
amplifier, the input tube has maximum bandwidth and the
least interaction with the source impedance (and the interconnect cable between the source and
the Truth
™
amplifier). We’ve done all the hard work of calculating turns ratios, impedances, and
system bandwidth. All you have to do is turn the volume to the level you prefer.
The 2-stage triode circuit uses the Z-Direct Interface
®
, with all tubes operated in a stable fixed
bias mode. The Z-Direct Interface
®
, unlike conventional RC-coupling, does not store energy,
and does not “block” when the 2A3 draws grid-current. This provides immediate recovery from
overload, and the impression of a much more powerful amplifier than the steady-state RMS
power rating. The Z-Direct Interface
®
also presents a low source impedance to the 2A3 grid,
which optimizes slew rate and gives the widest possible bandwidth.
The output of the 6DJ8 and the Z-Direct Interface
®
benefit from symmetric dynamic loads on
the plus and minus side of the circuit. The dynamic impedance is both high (orders of magnitude
higher than the plate resistance of the 6DJ8) and symmetrical, so the 6DJ8 operates in the most
linear region, with a flat load-line. Driver linearity is an important consideration with an output
tube as linear as the 2A3; there’s not much point in having a super-linear output tube if the driver
has more distortion, is there? That’s where the Z-Direct Interface
®
and the symmetric dynamic
loads come in; they provide the most linear working environment for the 6DJ8, as well as a stable
operating environment.
Capacitor coloration (a notorious problem in tube amplifiers) is avoided by the Z-Direct
Interface
®
. Unlike conventional amplifiers, there is no RC-coupling between the input and output
tube. In addition, there are no cathode resistors with capacitor bypasses, which sidesteps the
problem of finding large-value caps that are free of capacitor artifacts. Last but not least, there
is no cap coloration from the power supply; all tubes are powered directly from super low noise
regulators, which isolate AC line noise and AC line variations from the audio circuits.
DESIGN FEATURES