17
TUBE ULTRA-Q T1951
kind be identified and eliminated, before the actual musical fine-tuning of the sound image takes place. Still,
extreme settings can be realized by overlapping the frequencies of the individual bands.
4.4 On phase shift and time delay
Any analog filter, be it graphic or parametric, produces a certain amount of phase shift.
Particularly in narrow-band filters this phase shift leads to specific delay of the audio signal: the narrower the
filter and the higher the gain, the greater the time delay. In certain applications, the effect on the sound image
can be annoying.
Although the TUBE ULTRA-Q, owing to its unique concept, produces considerably less phase shift and hence
time delay than conventional parametric equalizers, this effect should nevertheless be taken into account.
+
Please also note that filters show a natural tendency to produce a ringing sound as their
bandwidth is narrowed, an effect that is caused by system-intrinsic noise modulation that
occurs with any kind of filter. It is therefore recommended that you set all filters not in use to a
mid-travel position or simply switch them off to minimize these side effects as effectively as
possible.
4.5 Tubes used in the TUBE ULTRA-Q
A closer look at developments and trends in audio technology shows that tubes are currently enjoying a
renaissance, in a time when even amateur musicians are free to use digital effects processors and recording
media, and ever more affordable digital mixing consoles are becoming a natural part of the equipment of many
semiprofessional studios. The manufacturers try with ever new algorithms to get the most out of DSPs (Digital
Signal Processors), the heart of any digital system.
Still, many audio engineers, particularly old hands often prefer using both old and new tube-equipped devices.
As they want to use their warm sound character for their productions, they are ready to accept that these
goodies produce a higher noise floor than modern, transistor-based devices. As a consequence, you can find
a variety of tube-based microphones, equalizers, pre-amps and compressors in todays recording and
mastering environments. The combination of semiconductor and tube technologies gives you the additional
possibility of using the best of both worlds, while being able to make up for their specific drawbacks.
4.5.1 Tube history
Due to many patent litigations, it is difficult to determine exactly when the tube was born. First developments
in tube technology were reported between 1904 and 1906. It was a research task of that time to find a suitable
method for receiving and rectifying high frequencies. On April 12, 1905, a certain Mr. Fleming was granted a
patent for his hot-cathode valve which was based on Edisons incandescent lamp. This valve was used as a
rectifier for high-frequency signals. Robert van Lieben was the first to discover (probably by chance) that the
anode current can be controlled by means of a perforated metal plate (grid), one of the milestones in the
development of amplification tubes. In 1912, Robert van Lieben finally developed the first tube for the amplifica-
tion of low-frequency signals. Initially, the biggest problem was to produce sufficient volume levels, which is
why resonance step-ups (though impairing the frequency response) were used to maximize the attainable
volume. Later, the objective was to optimize the electroacoustic transducers of amplifiers in such a way that a
broad frequency band could be transmitted with the least distortion possible. However, a tube-specific problem
is its non-linear amplification curve, i.e. it modifies the sound character of the source material. Despite all
efforts to ensure a largely linear frequency response, it had to be accepted that tube devices produce a bad
sound. Additionally, the noise floor generated by the tubes limited the usable dynamics of connected storage
media (magnetic tape machines). Thus, a one-to-one reproduction of the audio signals dynamics (expressed
as the difference between the highest and lowest loudness levels of the program material) proved impossible.
To top it all, tube devices required the use of high-quality and often costly transducers and sophisticated
voltage supplies.
With the introduction of semiconductor technologies in the field of audio amplification it soon became clear that
the tube would have to give way to the transistor, as this device featured an enormously enhanced signal-to-
noise ratio, less complex power supply and improved frequency response. Plus, semiconductor-based circuits
can be realized much more easilyfor less money. Two decades later, the introduction of binary signal
processing meant the beginning of a new era of recording media that provided plenty of dynamic response and
4. TECHNICAL BACKGROUND
All manuals and user guides at all-guides.com
