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1. INTRODUCTION
BEHRINGER ULTRAMATCH is an essential tool for modern recording studios. The importance of digital
technology has grown immensely during the past years in home-recording as well as in semi-professional
and professional studios. More and more operations are executed on the digital level. As a result, sound
engineers and musicians are confronted with a multitude of new connectors, signal leads, and changed
standards. Incompatibilities between two different devices are normal, and very often it turns out to be
impossible to interconnect two devices from different manufacturers.
This situation made us develop the ULTRAMATCH - a multi-functional device that meets all the requirements
modern studios expect. The ULTRAMATCH combines functions such as a digital patchbay, a signal refresher,
an SCMS eraser, a jitter killer, a format converter, and an excellent sample rate converter within a single unit.
Nevertheless, it is extremely user-friendly.
1.1Some Words on Digital Sample Rate Conversion
Up to now, the conversion of various sample rates has necessitated an enormous amount of components, and
yet has had manifold drawbacks, resulting in measurable signal falsifications such as increased noise, distor-
tion, or unwanted mirror frequencies (high-frequency chirping). The new processor employed in the
ULTRAMATCH executes a real-time conversion with total precision. It works absolutely stealthily, and its
influence on the signal can be detected only by means of very expensive measuring instruments.
Let´s look at a model to explain this operation which describes the conception of interpolation and decimation
of sample points. The processor performs an oversampling on the input signal, i. e. further samples are set
between each two regular samples, resulting in a larger total number of samples by this filling of the gaps. An
equivalent oversampling with a factor of 65,536 corresponds to an internal sample rate of 3.2768 GHz. After-
wards, the signal is run through a variable low-pass filter, ensuring a correct aliasing limit. This process is
started automatically whenever the sample rate at the output falls below the one at the input. Then, the number
of sample points is reduced by division until the desired sample rate can be established at the output. Due to
this enormous oversampling, the processor operates accurately over the entire audio-frequency band. Simulta-
neously, any jittering present in the input signal is removed.
No doubt, digital signal processing provides extremely low THD and noise values. However, signal recalcula-
tion especially in sample rate conversion used to lead to considerably non-linear results which is not surpris-
ing. The amount of data created in the interpolation model described above would totally overstrain conven-
tional technology. 10 Mbytes of data per minute would have to be stored in standard stereo sampling. Multi-
plied by 65,536, there would be a data amount of 650 Gbytes! Even if this data were processed in small
packages in order to avoid storage problems, sensible operation would be impracticable. Therefore, program-
mers have developed various algorithms that always used to be only a compromise between arithmetic ex-
penditure and sound quality.
However, despite real-time data processing, the BEHRINGER ULTRAMATCH obtains fantastic results. The
achieved noise level is below -120 dBFS and the distortion values are below -95 dBFS even at most complex
input signals. That means that the processing executed by the ULTRAMATCH remains inaudible, since
neither conventional A/D and D/A converters nor the final product - the CD - can achieve approximate values.
1.2The AES/EBU and SPDIF Standards
During the past decade, two standards have been established for digital audio transmission (see table 1.1).
The AES/EBU standard defines a professional balanced connection with XLR connectors, whereas the semi-
professional SPDIF standard (developed by Sony and Philips) makes use of RCA or optical connections with
light conductors. However, the SPDIF method standardized in IEC 958 has rather become known for its
notorious copy protection.
1. INTRODUCTION