termination of a transmission line (like a clock distribution line, for instance) is as follows:
A proper termination tells the signal to stop!
Black Lion Audio clocks are terminated at the source (the clock output) with a 75 Ohm
termination. This is done to properly drive a 75 Ohm cable and has the effect of “killing” any
reflections that come back from the line. Reflections are most commonly caused by
unterminated “stubs” on the line, like an unterminated clock input for instance.
Note that although it is possible to use “Tee” connectors and “daisy-chain” multiple converters
clock inputs from a single clock source, this is not the preferred method as this is how stubs are
created. Terminating each stub on the line does not work either, as multiple terminations load
down the source (the circuit driving the clock output) unnecessarily.
After much experimentation and after seeing different approaches tried throughout the industry,
we have found that this approach (multiple “T”s and terminations) becomes overly complicated
quickly, and often confuses even technically competent users.
The preferred method we have found is to use a “source-terminated” output (like a Black Lion
clock output) to drive one, and only one, un-terminated input directly through a short cable run.
The unterminated input does cause a reflection but, because of the source termination, the
reflection is negated at the beginning of the line and the input sees only the original intended
clock signal.
To recap; clocking BLA devices is simple:
* Drive one and only one clock input from a clock output.
* Use short, high quality, cables.
* Avoid “T” splitters and terminations if possible.
If you do not have good cables, or are still confused, DON’T PANIC! Black Lion can help. Just give
us a call and we’ll help you get your ADC up and running in no time.
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