Reprinted from October 2000
equipment
review
Digital Audio Denmark
ADDA 2402 Audio Converter by Dr. Frederick J. Bashour
B
ecause I regularly record at 24/96-resolution, Pro Audio Review tends to send
me all the latest high-tech converters to
review. I’m doing quite a bit at 192 kHz these
days, but I still consider 24/96 to be the standard for good sound quality. When I was told
that a Digital Audio Denmark ADDA 2402
was on is way, I started watching for the UPS
truck almost immediately.
I had plenty of other 24/96 converters on
hand with which to compare it (Apogee
Electronmics, Merging Technologies, dCS,
Lucid), so I set about to configure my studio
for the proverbial shootout.
Features
The Digital Audio Denmark ADDA 2402
is a single-rack-space unit with a stylish,
white front panel. It is a stereo ADC and
At a Glance
Applications:
Recording; mastering.
Key Features:
24-bit ADC and DAC sections clocking at all standard sampling rates
between 32 and 96 kHz; unit also
features sample rate conversion
from any standard digital input
frequency (32-96 kHz) to any different output frequency.
Price:
$1,995
Contact:
Digital Audio Denmark/Sascom at
905-469-8080; www.sascom.com
DAC, as well as being an SRC (sample rate
converter.) It can convert from analog to
digital and digital to analog simultaneously,
but one cannot m onitor in EE mode
(through all the electronics) without physically patching between one of the digital
output ports, and a digital input.
The 2402’s nearest competitor, the Apogee
PSX-100 (reviewed in PAR 9/99, p. 22) can
link its two sections internally. Indeed, this
unit will ultimately be compared with the
19 horizontally arranged signal strength
LEDs. The pushbuttons control the selection of analog input, digital input, digital
output source, sample rate clock, dither
resolution (24, 20, 16 bits), clock synchronization and power.
The different input sensitivity levels of the
two sets of analog connectors and the different output levels provided at each of the two
sets of analog output jacks are +4 dBu for the
unbalanced connectors and +18 dBu for the
PSX-100, since that unit is another singlerack-space box which is also an ADC and
DAC — although not an SRC. While each
unit has various features that differentiate it
from the other, both boxes address the same
prospective purchaser.
The ADDA 2402’s rear panel has analog
input connections for both balanced XLR
and unbalanced 1/4-inch plugs, switchable from the front panel; interestingly,
the two sets of inputs operate at different
levels; more about this later. There are
three sets of digital inputs and outputs:
AES/EBU on XLR, S/PDIF on RCA, and
o p ti c a l on T O S li n k, s e l e ct ab l e b y a
switch on the front panel. Digital outputs
are available in the same three formats
simultaneously.
Analog signals are output from the same
two types of connectors and circuits as the
inputs; these also operate at different levels.
The rest of the rear panel fe atures the
typical IEC AC power connector (110 or
220 V) and an AES/EBU external sync
input XLR jack (AES 11).
The c onverter’s front panel contains
seven gray, rectangular pushbuttons (with
associated LEDs) and a set of two pairs of
XLRs. This means that 0 dB FS — full scale
digital, all 0s — requires +18 dBu from your
mixer or microphone preamp if you’re
sending input through the balanced XLR
inputs. If you use the unbalanced inputs, only
+4 dBu are needed to drive the ADC section
to full level. So far so good — in fact, it’s
nice to have two different sets of input connectors selectable on the front panel.
The bad news, however, is that there are
no input (or output) trimmer controls whatsoever. Analog input levels must be controlled before the 2402 and output levels
after it. I consider this a serious omission,
as every other co nve rte r I hav e ever
owned, as well as every modern box I have
in my studio features such adjustments as
standard equipment.
Whether they have regular input and output-level pots (like the diminutive Lucid
boxes I reviewed in the 12/99 PAR, p. 32)
or recessed trim pots (as featured in converters by Apogee, dCS, Merging Technologies
and Prism), such adjustable controls make
analog calibration and level optimization
possible.
With the 2402, one must set the final input
level at the mixer or mic preamp. This isn’t
Copyright 2000 by IMAS Publishing (USA), Inc. Reprinted with permission.
such a bad idea in theory, but the fact
remains that good engineering practice recommends at least 10 dB of headroom in the
analog domain above whatever level is to
be 0 dB FS, in the digital domain. That
requires analog equipment which can put out
a clean signal when peaking at +28 dBu.
Such analog levels with high headroom are
attainable on well-designed tube equipment
and expensive solid state gear, but such gear
is not universally present in the marketplace.
Consequently, to avoid possible clipping of
peaks upstream in the analog domain when
using equipment with less headroom, one
would be forced to use the 2402’s unbalanced inputs and — if your analog gear happens to have a balanced output, one would
have to unbalance it.
In use
So what does the ADDA 2402 sound like?
In two words: clear and warm. Readers of
my other converter reviews might remember
that I consider the typical warm Apogee
sound as the yang to a clear, crisp converter’s yin. The Danish ADDA 2402 is the first
clean, clear and crisp-sounding ADC/DAC
combination that I would also label as warm.
Its designers, Mikael Vest and Peter
Scheelke, make a big deal about the special
filtering technique they use. The ADDA
2402 claims to implement considerably
more effective stop-band filtering than other
convert ers and thus reduces Aliasing
Intermodulation Distortion (AID), which can
occur when typical digital aliasing distortion
interacts with the intermodulation distortion
produced by D/A converters, amplifiers and
analog transducers such as loudspeakers.
Indeed, raunchy sounds like sibilants —
reproduced through less-than-perfect analog
equipment — sound considerably smoother
output from the ADDA 2402 than from
other converter gear to which I was listening. The theoretical tradeoff of their special
circuitry, however, is that the filter’s transition band starts a little lower in frequency
than is typical with other converters.
I listened to all the converters I had in the
studio to get an idea of where the ADDA
2402 fell in the sound continuum, but eventually did most of my comparisons with the
Apogee PSX-100. Regardless of the analog
signal source (but more pronounced with
dynamic, complex waveforms), the ADDA
2402 sounded bigger, brighter and ballsier
than the Apogee while somehow avoiding
the clinical sound character I often associate
with my “yin” equipment.
High-frequency information, such as cymbals, har psichords and voca l sibilants,
sounded quite a bit sweeter when converted
through the ADDA 2402. The low end —
while not possessing that little mid-bass
warmth I hear in all Apogee converters —
sounded both deeper and tighter with just
about all the program material I could find
to feed the two units.
I also found it interesting that the 2402’s
analog output circuitry was much less sensitive to the loading introduced by the $10,000
Solid State Logic-issued quad-level pot in
my Coleman Audio MS8 analog-balanced
input switcher. One click down from full on
really knocke d down quite a bit of the
Apogee’s output, while having minimal
effect on the ADDA 2402 circuit’s stated
40-ohm output impedance.
Product Points
Digital Audio Denmark
ADDA 2402 Audio Converter
Plus
• Great sound
• Versatile functionality.
Minus
• No input or output level
adjustment facilities
• Sample-rate conversion circuit
is not up to the quality of its
A/D and D/A converters.
The Score
If you’re looking for a great
sounding 24/96 recording and
monitoring conversion system
— and can adjust your levels in
the analog domain before
and/or after this unit — you
owe it to yourself to audition
the ADDA 2402.
I then listened to its SRC circuit. I had
three other SRC boxes on hand in my control room: the Weiss SFC-2, the dCS 972
and the new Lucid SRC 9624. Admittedly,
all three are pieces of gear dedicated to D/D
sample rate conversion — and they list
between $2,000 and $7,000 — but I still
couldn’t help compare those oranges with
this apple. I’m afraid to report that the old
adage “You get what you pay for” certainly
applies here. I’ve already reviewed the two
expensive SRC boxes — the Weiss and dCS
units — in PAR’s June 2000 issue (p. 58)
and although they sound slightly different
from each other, each sounds vastly superior
to either the Lucid or the SRC circuit in the
ADDA 2402.
In truth, there’s an actual difference in the
sample rate conversion processes as used by
the gear at each of the two price levels. The
expensive SRCs use synchronous conversion, while the Lucid and the ADDA 2402
employ asynchronous conversion.
In asynchronous conversion, as used in the
Danish box, the filter coefficient sets have to
Copyright 2000 by IMAS Publishing (USA), Inc. Reprinted with permission.
be calculated on the fly, as the input/output
sample rate ratio changes all the time. Thus
there is said to be some coefficient jitter
caused by the small variation of input/output
sampling frequencies. In a synchronous
design, the ratio is fixed and so the coefficient sets used in the filters are fixed as well.
Jitter in the sampling frequencies cannot
influence the sound quality. The drawback is
that there can’t be arbitrary ratios between
input and output sampling frequencies, such
as are involved in pull-ups and pull-downs.
Unfortunately, the sound quality produced by the two processes is very different — at least insofar as my experience
with two boxes of each type is concerned.
The a synchronous t echnique seems to
result in harsh highs, hollow mids and
seemingly reduced low frequencies. The
Di git al Au di o D enm ar k AD DA 24 02
seems to suffer from this malady more than
the Lucid 9624 box does.
Note that the Lucid SRC 9624 only does
sample rate conversion, however, and costs
the same as the ADDA 2402, which does Ato-D and D-to-A conversion as its primary
function. I think it’s nice that the designers
threw in one more feature, while still keeping
the price at $1,995 but, make no mistake
about it — the quality of its sample rate conversion is not as good as other dedicated asynchronous conversion boxes on the market.
Summary
As you can tell, I had mixed feelings about
the Danish Audio ADDA 2402. Its sound
was unlike that of any other converter I own,
and I quite liked it — as an ADC and a
DAC, that is. Its sample rate conversion feature, however, didn’t sound very good. And
while it lacked some of the monitoring possibilities of the Apogee PSX-100 as well as
the potential to output 24/96 digital audio
data bit-split to multiple tracks of 16-bit
MDMs, it is definitely in the same ballpark
— in the conversion world — as that more
expensive American unit.
Its relatively low input sensitivity, and lack
of input sensitivity controls (as well as that
slightly less important feature — control of
output level) is a drawback, however. Setups
other than mine might more easily tolerate
this omission. If Digital Audio Denmark
were simply to increase the gain of its analog input stage and include input and output
trimpots on the rear panel, I’d definitely give
it a thumbs up for its clear and warm sound
quality.
Dr. Fred Bashour is a jazz pianist, church
organist, classical music producer/engineer,
intermittent college professor, consultant to
university music libraries on the digital stor age of course listening materials and Pro
Audio Review contributor.