zapco DAII-SL, Owner'S Manual

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“Use Safe Sound” . Having properly set gains will allow you to
comfortably play the system at a much higher SPL, the fact that it is now
more comfortable to play at a higher SPL does not mean it is safer. The
functioning devices in your ear do not have very good pain receptors; even if
it does not “feel” like it hurts, excessively high SPL absolutely will damage
your hearing. So, please practice safe sound!
Cumulative Error
An issue that often is debated is at what level does distortion
become detectable to the human ear? Is there truly an audible difference
between a unit that measures .05% THD and one that measures .1% THD?
There are many who contend, with good cause, that distortion does not
become audible until the magnitude approaches 1% or more. Why do we go
to such great lengths in order to ensure the accuracy of each unit when
such minute differences are most likely inaudible?
The answer to this question underlies ZAPCO’s entire design
philosophy and is based on the simple concept of cumulative error. To
understand the point you must consider all the pieces of electronic
equipment that comprise the chain between the original performance and
your ears. From the microphone used to record the performance, to the
speakers used to reproduce it, the ultimate accuracy of the final output is
directly dependent on the accuracy of all of the pieces that comprise the
system. Given that this is not a perfect world, it is inevitable that each piece
of equipment will add some distortion or error to the original signal, and
signal degradation along this chain can be nothing but cumulative. It is the
cumulative error of the system as a whole of which we must be mindful.
From ZAPCO’s perspective, the idea that .1% THD, inaudible in and
of itself, is good enough, is unthinkable! If .002% THD is possible it is the
obligation of the manufacturer to do all that is feasible to attain that
maximum level of performance.
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