Owner`s manual

Dynamic Range
Dynamic range represents the difference between the maximum signal that
can be recorded and the “noise floor”, or level of noise with no signal
present. A system with a high dynamic range will be quieter than one with a
lower dynamic range. Dynamic range is a very important specification and
Your Echo hardware uses converters that have very high dynamic range.
Theoretically, a 24-bit system has a dynamic range of 144dB and a 16-bit
system has a dynamic range of 96dB. Two questions immediately come to
mind:
1) Why does my Echo hardware only have a dynamic range of 106 dB?
2) For mastering 16-bit CDs with a dynamic range of 96dB, isn’t
anything more than 96dB just overkill?
First, today’s analog to digital converters typically produce a full-scale input
voltage with an input of +7dBu. If they were to have 144dB of dynamic
range, they would have to be capable of resolving signals as small as –
137dBu (7dBu – 144dBu) or approximately 10 nano-volts. That’s 10 one-
billionths of a volt! Transistors and resistors produce noise in this range just
by having electrons moving around due to heat. Even if the converters could
be perfectly designed to read these levels, the low noise requirements of the
surrounding circuitry such as power supplies and amplifiers would be so
stringent that they would either be impossible or too expensive to build.
In answering the second question, consider the fact that music is often
compressed or amplified after it is recorded, and that some headroom is
necessary when recording to avoid clipping. The only way that 96dB would
be adequate is if all music were recorded so that the peaks were just under
full-scale and no compressing or amplification was going to be applied after
recording. Any time recorded music is amplified, so is the noise at the low
end. Your Echo hardware has enough dynamic range to allow sufficient
headroom and post-processing to be applied while still keeping the noise
either off the CD completely or down as far as possible.
70