Transparency defined
Analog pro audio routers should be transparent. It is not so obvious how that can be
specified. In the audio context it is about the difference between input and output signal.
It can be different in 3 ways.
The overall level is different.
Distortions in the output signal.
Phase response deviations in the output signal.
The level difference has the most impact on the perception of transparency and can be,
within limits, compensated for. Distortions and phase response deviations cannot
be undone. It is therefore important that these have low values and are not audible. All these factors are
separately measured and provided. There is however another, much more simpler way of measuring transparency as a
single figure that gives more insight to what's really going on. It is called a null test, the result parameter is called
"Correlated Null Depth" and it is in fact the level of the difference between the 2 signals under test.
Signal 1 is coming from the direct cable connection and signal 2, in our case, the same signal coming
through the router. Usually the levels from both test signals are made equal because it can give unreasonable results otherwise. Even
the slightest difference in level has serious impact on the test result. It makes sense because the difference between the tet signals
is usually at a very low level. When one of the test signal is just a little louder as the other level then the difference
between the test signals can be many times as high compared to equal leveled test signals.
There is an interesting thread here about "Correlated Null Depth" and converter transparency
Evaluating AD/DA loops by means of Audio Diffmaker. XBay has a Correlated Null Dept of 112.5dB,
which is a lot higher=better than the cleanest converter. Which also proves, apart from accumulating latency, that you
don't want AD/DA based signal routing when transparency is what you are after. The $50 patch point price also invalidates the
idea that working in the digital domain is more affordable. And with our routers the convenience of working in the analog domain
greatly surpasses, the apparent, convenience of working in the digital domain. Digital is for tracking, not for sourcing and/or processing.
Audio Precision is the recognized global standard in audio tests. We therefore have our products
externally specified by an independent specialist. The report can be downloaded here XBay test report.
The Audio Precision results are absolute, so that it is clear where the product stands relative to all other products that are also
specified with Audio Precision equipment. During development
or internal benchmarking against other products, we use our own AD/DA and software to see where we are at relative to ourselves
or other products. The values are in that case less precise in isolation and not suitable for a product specification but for comparison
between products in a benchmark, these result are precise enough for the context.
