14
Track One
MAKE UP GAIN
With the MAKE UP GAIN control you can restore the overall level reduction caused by compres-
sion or limiting. With assistance of the GAIN REDUCTION display setting the MAKE UP GAIN
control is made easy: If the maximal reduction value caused by the loudest tone amounts to
-9 dB, for instance, the MAKE UP GAIN control should be set to values 9 dB. If the
compressor/limiter is now switched off the achieved gain in loudness will be audible.
SPL compressor technology
In the compressor/limiter section of the Track One the parameters for the time constants
(attack and release) are set automatically and adapt themselves to the changing conditions
of the input signal, far better than can ever be achieved by manual adjustments. The transient
and final oscillation behavior of voices and instruments are constantly changing and at times
are so erratic that a manual control will only achieve good average values, which at critical
moments can produce disadvantageous effects (e. g. distorted sounds, “pumping”, etc).
If for example the compressor has to react very quickly to harsh P or T noises it must also
be capable of reacting slowly to softer tones – otherwise distortion occurs. Accordingly the
Track One compressor regulates the level of large fluctuations faster than smaller ones; tones
of longer duration are automatically processed with a longer attack time to prevent distor-
tions.
The automatic setting of the release times is dependent on the input signal, too. Fast and
large level fluctuations are correspondingly processed with shorter time constants than minor
fluctuations in order to limit the distortion of the audio signal as far as possible. Overall this
technique provides the optimal solution between fast, unobtrusive control response and the
least distortion of the audio signal. The result is a natural and transparent sound impression.
A further technical specialty of the circuitry contributes to the high audio quality of the
compressor in the Track One: SPL’s double VCA drive. One VCA receives the in-phase, the
other the out-of-phase signal. Subsequently the signal is passed through a differential ampli-
fier. The effect of this circuitry is that distortion products and offset fluctuations can be
removed – the product of the differential of both signals means that possible interference is
canceled out. The original information is however further amplified by 6 dB. In addition the
VCAs provide relief to each other because they share their loads. They do not even run the
danger of operating in the saturation range, which ensures to avoid offset noises, audible as
clicks or pops.
SPL’s double VCA drive circuitry overall displays vastly improved distortion values so that a
distinctly clearer and more transparent sound impression is achieved than with conventional
circuitry. Voices and instruments are given a considerably more natural and dynamic timbre
whereas ”muffled” tones are not audible.
The compressor characteristics are portrayed on page 20.
Control Elements
Compressor/Limiter
