PLEASE NOTE: This article has been archived. It first appeared on ProRec.com in February 2000, contributed by then Product Review Editor Jim Roseberry. We will not be making any updates to the article. Please visit the home page for our latest content. Thank you!
When working with digital audio, your system’s analog-to-digital (A/D) and digital-to-analog (D/A) converters will ultimately determine the fidelity with which you can capture and playback audio.
This is an area where many people getting started with digital audio get confused. “My converters are the latest 24/96 converters,” they say. “Isn’t 24/96 what I want?”
Converters: What Goes In Must Come Out
The simple fact is that not all converters are created equal.
True, inexpensive 24-bit converters are improving all the time. True, many newer audio interfaces like MIDIMan’s Delta 1010 provide very respectable performance (109dB dynamic range). True, for most purposes, this is more than adequate. However, if you wish to attain top performance, you’ll have to go with a dedicated set of A/D D/A converters.
So what’s available? Many studio owners want world-class performance, but can’t justify spending $3000 for a pair converters – especially when their existing converters are already pretty darned good.
So what’s a typical studio owner to do?
For the past couple of months, I’ve been using a set of outboard Swissonic AD96 and DA96 converters, and wanted to share the experience.
Yodel Ley Eee Who?
Swissonic is a company based in Uznach, Switzerland, with Swissonic America being the US branch. Many folks are probably not familiar with the Swissonic name, but are actually using units designed and built by Swissonic.
When you look at several of the Swissonic products like the AD24 and DA24, you’ll probably notice that they look vaguely familiar. This isn’t coincidence. Swissonic is the company that actually manufactured A/D D/A converters sold under the Sonorus name.
The Swissonic AD96 is a half-rack 4-channel 24Bit A/D converter with balanced XLR inputs and both ADAT lightpipe and AES/EBU outputs.
The first thing you’ll notice about the AD96 is that is has a sturdy steel chassis. It’s actually fairly heavy for a half-rack unit. The only moving parts are seven push-buttons and a rocker power-switch. There’s not much that can wear out, although the push-buttons feel just a tad fragile.
The AD96’s user interface is about a simple as it gets. On the left side of the unit, you’ll find four LED peak-meters, each with 16 steps. To the right of the meters, there are push-buttons to select the various options for Meters, Clock Source, Wordclock Output, Output Resolution, Sample Rate, and ADAT Format. There’s also a button to Calibrate the converters. Pushing each button cycles through its options, indicated by a green LED.
Let’s Run the Numbers
The AD24 offers impressive features and performance. Here’s a quick run-down of what you can expect:
- True 24Bit A/D conversion
- 7th order, tri-level delta-sigma converter architecture
- 4 balanced XLR inputs
- LED meters for input monitoring (w/multiple modes)
- Low-noise L/C PLL system
- BNC Wordclock I/O (1x, 2x, Superclock)
- Conversion between Wordclock formats
- 44.1kHz, 48kHz, 88.2kHz, and 96kHz sample rates
- Lightpipe optical output (4-channels; switchable between 1-4 and 5-8)
- S/MUX and B/MUX format options
- Noise-shaped Dither (switchable between 16, 18, and 20Bits)
- Two AES/EBU outputs (XLR)
- Dynamic Range: 118dB A-weighted, 113dB unweighted
- THD + Noise (20Hz to 20kHz): -100dB @ -1dBFS input, -95dB @ -20dBFS input, -53dB @ -60dBFS input
- THD: 0.001% @ -1dBFS input
Using the AD96
One great thing about using the AD96 is that it offers very flexbile and informative metering. When working with digital audio, there’s nothing more frustrating than not knowing where the “top” is. You’re cruising along, happily recording you next opus, and SPLAT go the converters. Here’s where an excellent set of meters are worth a lot more than just pretty eye candy.
The AD96 offers four metering options that allow you to really get the job done right.
-60 / 0dB: From –60dB to -21dB… the meters provide 5dB steps, from –21dB to 0dB… the meters provide 3dB steps
-15 / 0dB:The first green LED (@-60dB) is a ‘channel active’ indicator, from –15dB to 0dB… the meters provide 1dB steps
-25 / -10dB: The first green LED (@-60dB) is a ‘channel active’ indicator, from –25dB to –10dB… the meters provide 1dB steps, the Red LED is an ‘over’ indicator
Overloads: The first green LED (@-60dB) is a ‘channel active’ indicator, the Red LED is an ‘over’ indicator, the middle LEDs show the number of ‘overs’ using a logarithmic scale.
In order to be useful in a variety of situations, the AD96 must be able to lock onto many different clock sources. Four clocking options are available on the AD96 to ensure that it will work in virtually any digital studio: Internal, 1x Wordclock, 2x Wordclock, and Superclock (256x). The AD96 will also present any of these clocks (1X, 2X, and Superclock) on its Wordclock outputs.
The AD96 fully supports all popular bit depths and sample rates. Bit depth is selectable from 24, 20, 18, and 16 bit depths. Dithering and noise shaping is applied to the output when using any of the lower bit depths (20, 18, and 16) to ensure the best possible sound quality. Available sample rates include 44.1 KHz, 48 KHz, 88.2 KHz, and 96 KHz.
So How’s It Sound?
In a word, excellent!
The perfect acid test for any set of A/D converters is recording acoustic drums. With their powerful attack and long decay, acoustic drums will highlight any problems with digital audio. I just happened to be in the middle of a massive acoustic drum project when the AD96 arrived, so I had a great opportunity to try out the AD96 in a truly demanding application. For these listening tests I would use a SEK’D 2496 D/A converter unit driving a pair of Mackie HR824 monitors.
I set the AD96 for 24Bit / 44.1k operation and recorded for about 10 minutes. Upon playback, it was quite clear that the AD96 is a world-class unit. The initial transient is where you immediately hear the difference. Lesser units tend to blur or smear the initial transient, reducing the impact of the drum, but transients recorded through the AD-96 are clear and well defined.
As a point of reference, I decided to compare drum recordings made on several sets of 24Bit A/D converters including the SEK’D 2496DSP and 2496s units, the MIDIMan Delta 1010, and the Swissonic AD96. I expected the more expensive units to produce better results, and that was pretty much the case. But what surprised me was that the AD96 actually outperformed the $3000 2496DSP, and was the best of the bunch!
Having determined that the AD96 is a first-class set of converters, I was anxious to record vocals and other instruments so I could further evaluate the character of the converters. After several tracking sessions including vocals, acoustic guitar, electric bass, and electric guitar, I feel confident in comparing the AD96’s character to that of Mackie mic preamps. The AD96 won’t fatten the bottom end, or enhance the mids or top end, but it will capture pretty much any source with great accuracy.
A Word About B/MUX and S/MUX
B/MUX, better known as bit-splitting, allows 16 bit lightpipe-equipped gear to record 24 bit audio. The 24 bit data is spread across two 16 bit tracks. When used like this, a standard 16 bit ADAT can be used to record 4 24 bit tracks. Of course, when using B/MUX, you’ll need a B/MUX compatible D/A unit like the DA96 to decode the B/MUX audio.
S/MUX allows the AD96 to record 88.2kHz or 96kHz audio to typical 44.1 / 48KHz machines. Similar to the way B/MUX spreads 24 bit data across two lightpipe channels, S/MUX outputs 88.2 KHz or 96 KHz audio across two output channels.
I’m not too thrilled with the S/MUX method of recording 88.2/96kHz audio. S/MUX (occupying two recorded channels) is a pain in the ass to deal with when recording into a DAW for editing / mixing, unless you have an S/MUX compatible audio card and audio application. If your audio card and audio application are S/MUX compatible (ie: Sonorus Studi/o and Logic Audio) the two channels are managed (merged) ‘behind the scenes’ and appear as a single 88.2/96kHz recorded channel in the application. I much prefer the AES/EBU outputs for 88.1 / 96 KHz audio! But this is a limitation of the ADAT Lightpipe format. Lightpipe doesn’t have the bandwidth to transmit 88.2/96kHz audio over a single channel, and S/MUX was developed to circumvent this limitation.
To be fair, S/MUX can breathe new life into an ADAT. Used together with B/MUX, S/MUX will allow an old blackface ADAT to record two channels of 24Bit 88.2/96kHz audio. Audio recorded via S/MUX (at 88.2kHz or 96kHz) sounds exceptional. If you have an old blackface ADAT that you hardly ever use anymore, B/MUX and S/MUX can turn that unit into a first-rate 24/96 mastering deck.
The DA96 is a half-rack 4-channel 24Bit D/A converter. Like the AD96, the DA96 has a sturdy steel chassis and features the same push-button/LED user interface.
The DA96’s user interface is laid out exactly like the AD96. On the left side of the unit, you’ll find four “activity” LEDs (signal present), four Peak LEDs, “Lock” LEDs for each digital input (ADAT, AES/EBU 1, AES/EBU 2), and error LEDs for each digital input.
To the right of the LEDs, there are push-buttons to select the various options for Wordclock Input, Clock Source, Wordclock Output, Data Source, Sample Rate, and ADAT Format. There’s also a button to mute the DA96’s output. Pushing each button cycles through its options, indicated by a green LED.
Features and Specs
Like its counterpart, the DA24 offers impressive features and performance:
- True 24Bit D/A conversion
- Low clock jitter sensitivity
- 4 balanced XLR outputs (capable of driving over 300m of cable)
- Activity and Peak LEDs
- Low-noise, dual PLL clocking system
- BNC Wordclock I/O (1x, 2x, Superclock)
- 44.1kHz, 48kHz, 88.2kHz, and 96kHz sample rates
- Lightpipe optical input (4-channels; switchable between 1-4 and 5-8)
- S/MUX and B/MUX format options
- Two AES/EBU inputs (XLR)
- Automatic detection of input resolution
- Clickless muting
- Dynamic Range: 112dB A-weighted, 109dB unweighted
- THD + Noise (20Hz to 20kHz): -94dB @ 0dBFS output, -88dB @ -20dBFS output, -49dB @ -60dBFS output
- THD: 0.002% @ -1dBFS output
Like the AD96, the DA96 will work easily with a variety of Wordclocks: 1x, 2x, and Superclock. The DA96 can lock to clock sources on the Wordclock input, the ADAT input, or either of the AES/EBU inputs. It can also present any of these Wordclocks on its built-in Wordclock output. This capability allows the DA96 to easily integrate into pretty much any digital studio. The DA96 also incorporates B/MUX and S/MUX decoding, making it the perfect partner for the AD96 when using ADATs. The DA96 also includes a Mute button – great when making connections or when things go wrong. The unit will self-mute when it cannot lock to an input source.
To evaluate the DA96, I listened to recordings of acoustic drums, vocals, and acoustic guitar – all recorded at 24 bit 44.1kHz via the AD96. This was an easy test. All tracks sounded excellent through my Mackie HR824 monitors.
As a point of reference, I listened to the same recordings on several sets of 24 bit D/A converters: SEK’D 2496DSP and 2496s, MIDIMan Delta 1010, and the Swissonic DA96. In this scenario, it was very hard to tell much difference between the four units. They all sounded good. If I had to pick a favorite, it would be a three-way tie between the 2496DSP, 2496s, and DA96. A quick look at the specs reveals that, unlike the A/D units, there is less difference between the various D/A units.
And now for the obvious question: so how do the AD96 and DA96 compare with top-flight Apogee converters?
A/D: I’ve mixed audio recorded with an Apogee PSX-100 and a Swissonic AD96, and I’d rate the AD96 a single notch below the PSX-100, or Rosetta. The primary difference between the units is that the Apogee units offer UV-22 dithering. The dither on the AD96 sounds fine… but it’s not UV-22. In any case, it’s very unlikely that you would be dissatisfieed with the sound of the AD96. At this level of sound quality, we’re talking about fine shades of grey.
D/A: Simply put, the DA96 easily holds its own against any top-rated D/A converters. It has all the features you’ll need and expect, and truly excellent sound. As previously mentioned, if you already have a good set of 24 bit converters in your I/O system, it’s unlikely that you’ll hear worlds of difference between them and the DA96. On the other hand, if your frame of reference is a blackface ADAT, please prepare to be amazed.
If you’re looking for a set of world-class A/D and D/A converters, and can’t stretch to the cost of Apogee, the Swissonic AD96 and DA96 should be high on your list.