Behringer M IC 2200 - Manual (Page 8)

8
ULTRAGAIN PRO MIC2200
It is therefore useful to keep the operating level as high as possible without risking signal distortion in order to
achieve optimum transmission quality.
t
P/dB
+20
0
-20
-40
-60
-80
Clipping
Headroom
Operating level
Effective SNR
Noise floor
Fig. 1.2: The interactive relationship between the operating level and the headroom
1.2 The tube used in the ULTRAGAIN PRO
A closer look at developments and trends in audio technology shows that tubes are enjoying a renaissance
today, 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 semi-
professional studios. Manufacturers try with ever new algorithms to get the most out of DSP’s (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 “little
darlings” produce a higher noise floor than modern, transistor-based devices. As a consequence, you can find
a variety of tube-based microphones, equalizers, preamps and compressors in today’s 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.
1.2.1 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 Edison’s incandescent lamp. This valve was used as a
rectifier for high-frequency signals. Robert von 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
amplification 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
signal’s 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.
1. INTRODUCTION