Loren Alldrin is Pro Audio Review's Project Studio Editor. His book, "The Home Studio Guide to Microphones," is available from ArtistPro.com.
The recording community is moving toward high-resolution audio recording, thanks in part to the DVD medium. Swissonic's AD96 A/D and DA96 D/A converters, which offer four channels of 24-bit recording at high sample rates (88.2 and 96 kHz) using the MUX processes, are aimed at this emerging market.
Product Points
Applications: Studio; mastering
Key Features: Four channels of 24-bit/96 kHz (or 88.2 kHz) conversion; S/MUX sample rate packing and B/MUX bit-depth packing to ADAT lightpipe; high-resolution metering (AD96); word clock and Superclock I/O; low-noise/low-jitter clock circuits
The Score: Great-sounding converters that allow high-bit/sample rate recording and playback to ADAT lightpipe-equipped records.
Features
Both the AD96 ($999) and the DA96 ($999) are half-rackspace units with simple pushbutton controls, rear-mounted connectors and a hefty wallwart power supply. Both have four balanced XLR connectors, dual AES/EBU digital jacks, lightpipe digital port and word clock/Superclock I/O. Other features in common include a 4mm banana ground socket and internal jumpers for -10 dBV operation.
To support its four channels of A/D conversion, the AD96 offers four high-resolution (16-element) meters on its left side. These meters work in four modes: -60 to 0 dB, -15 to 0 dB, -25 to -10 dB and overloads. In the latter mode, the meters count clipped samples in binary fashion.
Two or three overload LEDs lit is probably safe enough. Light them all, however, and you've just clipped more than 8,192 samples. Overs are continually incremented within the AD96, and can be cleared with the CAL button.
Six other buttons function in the same fashion as the meters button, cycling through three or four settings for clock source, word clock output, output resolution, sample rate, ADAT format and calibration mode. Four LEDs - with a legend above each button - show the selected mode.
Input clock options for the AD96 include internal, word clock x 1, word clock x 2 and word clock x 256 (Superclock). The AD96 cleans up whatever clock source it is given and makes it available on its word clock out connector. Along the way, it will convert the clock to any of the above word clock formats. The AD96 has a commendable clock circuit, with high jitter attenuation.
The next button selects output resolution - 16, 18, 20 or 24 bits. The AD96 automatically adds noise-shaped dither to any bit depth below 24 bits. Sample rates (the next button) include 44.1, 48, 88.2 and 96 kHz.
An ADAT format button offers four options, including Channels 1 through 4, Channels 5 through 8, B/MUX and S/MUX. At standard ADAT sample rates and bit depths, the first two options let you choose which bank of four channels the AD96's digital output appears.
The S/MUX mode does sample-rate splitting to run 88.2 or 96 kHz recordings down the lightpipe. Each high-sample rate channel then takes up two channels of the 44.1 kHz or 48 kHz lightpipe. Provided the AD96's output resolution matches the bit depth of your ADAT (16- or 20-bit), you can record four high-rate channels across the eight-channel tape.
The B/MUX button also packs high-resolution audio down the lightpipe, but it splits the data in two based on bit depth. Provided you match the sample rate of your ADAT (44.1 or 48 kHz), the B/MUX option lets you record four channels of 24-bit audio to eight ADAT channels.
If ADAT users don't want to be limited by the sample rate or bit depth of their ADAT, a double split is required, with both the S/MUX (sample rate) and B/MUX (bit depth) modes enabled. The result is a four-way split for each 24/96 or 24/88.2 channel, providing a high-resolution stereo recording that takes up all eight ADAT channels. Users of 20-bit ADAT have an additional option for getting four channels of high-resolution recordings. Instead of using the B/MUX mode to split 24 bits across two channels, leave B/MUX off and let the AD96 dither down to 20 bits.
At 88.2 or 96 kHz, the AD96 shifts its noise-shaped dither up beyond the audible band. This results in a 20-bit recording virtually indistinguishable from the true 24-bit variety. Users with 16-bit ADATs can dither the AD96's output down to 16 bits.
For getting back from digital to analog, the DA96 has a similar feature set to the AD96. Instead of 16-element meters, the DA96 has simpler active (-40 dB) and peak (0 dB) indicators for each of the four channels.
Lock indicators show the presence of a valid clock at the ADAT, AES/EBU 1 or AES/EBU 2 input; corresponding error indicators for each input show clock slip or data loss. The unit's data source and clock source buttons permit selection between ADAT and AES/EBU inputs. Other buttons function in similar fashion to those on the AD96, including sample rate and ADAT mode.
Inuse
With so many options for resolution, sample rate and ADAT mode, the Swissonic converters take a little time to get set up properly. You may have to sit and think for a few minutes about what you hope to accomplish with a given recording, then spend a few more minutes in trial-and-error mode setting up the units. Once you understand how the ADAT modes interact, things become much more clear.
With the proper mode enabled, the Swissonic converters generate truly remarkable sound. Their sound is both detailed and smooth, with a sense of depth you just don't get from standard recordings - the word "effortless" comes to mind when listening to the Swissonic converters. These units have numbers to back up what one hears, such as 118 dB S/N ratio and dynamic range specs for the AD96 (112 dB for the DA96).
The Swissonic manuals are a little terse where actual operation of the converters is concerned, but are full of good information on everything on balanced/unbalanced conversion, jitter, grounding issues, avoiding hum and more. Keep the manuals handy as general reference works for digital audio.
My only gripe with the Swissonic converters is the font used on the front panel graphics and legends. The number 1 looks like a 7, making it confusing to decipher the meter legends and other crucial text. 78 bits? Channels 7 through 4? Poor font choice, folks.
Summary
The Swissonic AD96 and DA96 converters offer stellar high-resolution recordings and playback - which actually is not all that special. What makes these converters stand out is that they make these types of recordings available without a high-resolution recorder.
Being able to pack 24/88.2 or 24/96 recordings onto a humble ADAT is a wonderful thing, and it opens up the world of high-resolution recordings to folks on a modest budget.
These converters aren't the first to work such magic, but they do so with stellar audio quality and minimum fuss. If you're looking for high-resolution converters that fit this description, check out the Swiss-made Swissonic AD96 and DA96 converters.
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