EC-2 96kHz A/D/D/A upgrade Y appendix A
About the EC-2Os audioWhen to use 88.2/96 kHz
performance
Why 44.1/48 kHz?
An HD24 with the EC-2 upgrade has audio
performance far superior to that of any analogMany engineers believe that the sampling rates that
recorder, and a wider dynamic range than mosthave been used up to now are less than ideal. The
input and output devices that may be connected toindustry-standard sample rates were chosen at a
it. HereOs why:time when digital storage was much more
expensive than it is today. The Oconsumer� rate of
The converter defines the sound44.1 kHz was the lowest possible sampling rate that
could still record and play back the highest
The first and last steps in digital recordingNthe
frequencies in the commonly-accepted human
conversion from analog to digital, then back
hearing range of 20 Hz to 20,000 Hz. At a 44.1 kHz
againNdefine the audio quality of the digital
sampling rate, a 650 MB Compact Disc would be
recording process. Once captured in the digital
able to play back 72 minutes without
domain as a series of ones and zeroes, the audio is
interruptionNthe length of BeethovenOs Ninth
protected for as long as the media lasts. So the
Symphony.
converter you use when recording a master is one of
the most important choices you can make in the
In an era before digital mixing consoles and
studio.
computer workstations, the 48 kHz sampling rate
was designated the Oprofessional� rate for two
The EC-2 upgrade uses premium AKM 5393 analog-
reasons:
to-digital (A/D) and AKM 4393 digital-to-analog
(D/A) converters, among the best available today.
1. the slightly higher sampling rate allowed
The input and output electronics are virtually
more room for the antialiasing filter to do its
identical to those of the acclaimed Alesis
work, and
MasterLink High-Resolution Master Disk Recorder.
2. professional recorders needed to be able to
Even at standard sample rates, the noise floor and
Opitch down� 12% and still play back the full
distortion are lower than most units costing much
20 kHz frequency range.
more. The noise floor is 10 dB lower than a Ostock�
HD24, and 20 dB lower than standard Compact
The case for a higher sampling rate
Discs and the original 16-bit ADAT. How much is
10 dB? From a laboratory standpoint, 20 dB standsWhile the traditional sampling rates give excellent
for 100 times the powerNso the dynamic rangeperformance (especially with todayOs converter
increase is analogous to the difference between a 10-technology), there is criticism that these rates are too
watt amplifier and a 1000-watt amplifier. Becauselow to obtain truly audiophile quality. Most of this
of the logarithmic nature of human hearing, to mostcriticism centers on the filters that are necessary to
people, each -10 dB of difference sounds Ohalf asmake digital audio work.
loud�, so the noise floor of the EC-2 will be
th
perceived as 1/4 that of a standard CD.Antialiasing filters
The Nyquist theorem, upon which digital audio
The resulting 112 dB dynamic range is not onlyrecording is based, states that you can reliably
more than that found on a standard Compact Disc,record and play back any signal by sampling it at
it is much wider than the acoustic dynamic range ofleast two times the rate of the highest frequency you
even the best recording studios. When you recordwant to record. However, if there are any analog
analog audio directly into an ADAT HD24frequencies in the incoming signal that are higher
upgraded with an EC-2, the recorder is literally nothan half the sampling rate, nasty-sounding
longer an issue in the overall sound quality. Evenreflections appear in the signal, known as aliases.
dedicated (and expensive!) outboard convertersFor example, if a 47 kHz tone is sampled at 48 kHz,
connected to the ADAT Optical ports of the HD24youOll hear a 1 kHz tone, right in the midband of the
have a tough time beating the specs of the EC-2.audioNhardly what youOd want to hear by getting
With proper recording techniques, any noise or hissOextended frequency response�.
you hear is coming from the self-noise of the
microphones or preamps, not from the HD24.So, early analog-to-digital converters had a steep
Obrick wall� analog filter on the input. To avoid
A-8EC-2 Manual |
ACEC
