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Now
that high-resolution digital audio workstations and modular digital multitrack
recorders have arrived, issues of adequate wordlength and sampling frequency
are largely being resolved, at least from a data storage perspective. But
the front ends of these devices, which contain analog circuitry, A/D converters
and word clock read/write systems, often fail to deliver the full potential
of high-resolution recording. As a result, several manufacturers have developed
8-channel A/D converters that serve as an alternative to the stock circuitry
found on MDMs/DAWs. Although the cost of these outboard converter sets have
historically exceeded that of the recorders they serve, prices are finally
coming down.
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At a list price of
$2,495, the Panasonic WZ-AD96M 8-channel A/D converter and mic preamp
offers a high-quality yet cost-effective front end for high-resolution
digital recording systems. The 1U, rackmountable unit’s eight wide-ranging
inputs accept mic or line level signals, and its 24-bit, 128-times oversampling
converters output 24-, 20- or 16-bit digital audio at 44.1, 48, 88.2 or
96 kHz sampling frequencies.
THE RIGHT
CONNECTIONS
All I/O connections are on the rear panel. Analog inputs for the WZ-AD96M
are provided via eight female, balanced, locking XLR connectors. AES/EBU
digital outputs are provided on four male XLRs. These can transmit either
eight channels of high-speed, Single-Wire AES/EBU data or four channels
of Dual-Wire AES/EBU data (more on this later). An ADAT lightpipe output
is also provided for 8-channel output, and an optional TDIF card can be
added for $395. Word clock in and through connections are provided on
75-ohm BNCs; moving two jumpers inside the unit’s chassis converts
the word clock thru to word clock out, sending the internal clock signal
to the connected device. Also on the rear panel are an IEC receptacle
for the detachable AC cord, a grounding screw to eliminate ground loop
hum and eight DIP switches.
The first DIP switch selects High-Speed, Single-Wire or Dual-Wire AES/EBU
output mode. There are a number of high-resolution audio devices on the
market that support one or the other, but not both modes of transmission.
The WZ-AD96M will interface with either type of equipment.
In High-Speed, Single-Wire mode, the balanced XLR accommodates two channels
of AES/EBU-format data on one wire. In Dual-Wire mode, only one channel
is sent per XLR. An optional output card, the WZ-AESAD ($395), provides
eight-channel 24/96 audio output in the Dual-Wire AES/EBU format via a
D-sub connector. The owner’s manual provides a pin out diagram for
making your own cables, or you can buy the Panasonic 96DB-XLRM, a three-meter
breakout cable that fans out a DB-25 connector to eight XLRs.
Another DIP switch works only if you’ve changed the WZ-AD96M’s
word clock thru to word clock out via the two internal jumpers. In that
case, this DIP switch makes the word clock output follow either the sampling
frequency set on the unit’s front panel or the AES output rate. This
can be useful because some recorders require 48kHz word clock (which they
double internally) to record 96kHz audio. Other DIP switches allow you
to customize the response of the WZ-AD96M’s front panel meters, which
we’ll discuss shortly.
FRONT PANEL CONTROLS
Each of the WZ-AD96M’s eight mic preamps has a continuously variable
gain pot and a 48V phantom power on/off button with its own status LED.
Maximum gain at the pot’s full clockwise position is 64 dB. Full
counter-clockwise position yields unity gain.
Maximum input level is +24 dBu. Although that may be a tad low for some
line-level mastering applications, I suspect most users will buy this
unit for tracking, given the included micpre’s. On the subject of
tracking, the unit’s main ergonomic drawback is the lack of inserts
or direct outs after the micpre’s. These would be useful for patching
in dynamics processors or alternative A/D converters, but were obviously
omitted to keep the price down.
A single, tri-color LED indicates signal/reference/peak digital meter
levels to 0.05dB accuracy. The LED lights green when signal level is present
but lower than the reference level. Previously mentioned DIP switches
adjust the reference level—indicated by an amber LED—between
–14 and –20 dBFS in 2dB increments. Other DIP switches adjust
the peak detection level (which lights a red LED) to 0.0 dBFS or -0.5
dBFS or in 1dB increments from –1.0 to –6.0 dBFS.
Although the 0.0dBFS setting will alert you to clipping, the WZ-AD96M
does not retain digital “overs” nor offer peak hold metering.
So, there’s no way to set up the unit to simultaneously alert you
to peak levels approaching clipping and digital overs. You must set it
up to do one or the other. However, this is not really an issue if your
recorder’s metering is comprehensive and in plain sight.
The unit’s reference level is also indicated by a separate, static
display on the front panel. This is a nice touch because it allows you
to see at a glance how your levels relate to other gear without having
to check calibration levels with an oscillator. It’s important to
realize, however, that the reference level adjustment affects only the
metering and does not affect the front end’s gain structure in any
way.
Go
to Page 2
Reprinted with permission
from 
Magazine, September, 2000
© 2000, Intertec Publishing, A Primedia Company All Rights Reserved
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