Mixing out of the Box, Part 1: High End Mixer Shootout
In recent months, there's been a bunch of talk on the various online forums about mixing digital audio tracks within your DAW vs. through an external analog mixer. A quick search on the Digidesign Users Conference, Mixerman's board on ProSoundWeb, or the forums hosted by MusicPlayer will yield hundreds of posts expounding on the differences between internal mix busses of various DAWs and how these busses hold up sonically against analog circuitry. Some of the posts are very technical in nature while others read as if they're the transcripts of witchcraft trials, complete with accusations and condemnations. A blind-comparison CD is even being offered by Lynn Fuston of 3D Audio, whom many of you know for his microphone and preamp CDs, so that engineers can make their own observations about the sonic character of the summing busses within various DAWs and digital mixers. One company that's found itself in the thick of this passionate and sometimes raging conversation is aptly named Dangerous Music. Dangerous Music specializes in high-fidelity analog solutions for digital audio recording. They were kind enough to offer us a Dangerous 2-BUS on a long-term loan. We asked Tape Op contributor and Grammy- winning producer and engineer Joe Chiccarelli to let us know how the unit sounds. Joe compared it to the cream of the crop when it comes to high-end mixing: the Pro Tools HD internal mix buss and analog consoles from SSL and Neve. Read the detailed account of his controlled listening tests below. In a future installment, we'll see what an external analog mix buss does to a dedicated "in the box" mix- engineer when we strap several different analog summing amplifiers to the outputs of his DAW for a couple months.
The Dangerous 2-BUS is a 16x2 analog summing amplifier designed to work with Nuendo, Digital Performer, Pro Tools, and other Digital Audio Workstations. To put it simply, the software mixers inside these DAWs are implemented with "Math." Within the context of digital signal processing, math has its limitations, whether it's done with integer or floating- point arithmetic. There are basic issues that affect the precision of all computer-based math, including propagation of rounding errors, numeric overload, and bit truncation. Even within seemingly simple DSP operations, like the summing of multiple channels of digital audio, these issues not only affect the sound, but they also force us to be extremely diligent with the gain structure of our software mix sessions. Finding workarounds for these limitations can leave us begging for an analog console. That's where the Dangerous 2-BUS comes in. With sixteen inputs, it allows you to combine sixteen channels of stems or direct analog outputs from your DAW via high-speed analog circuitry. You keep your automation in the DAW, but by bussing out to the 2-BUS, you bypass the internal summing buss of your DAW's software mixer. Advantages? You free up your DAW's processor for other tasks. You can run hotter internal levels, regaining bit resolution if you're otherwise pulling back levels to prevent overloading of the internal mix buss. And you have the option of inserting your favorite analog processors without an additional A-D conversion to get back into the DAW's mixer. These are all compelling reasons to go with a high- quality analog summing unit like the 2-BUS, both in terms of sound quality and in terms of workflow.
The 2-BUS is a solidly built, 2U rackspace box with a very lean front panel. A stepped Master Analog Gain knob allows you to vary the output level within a 10 dB range in 0.5 dB steps. There are two sets of eight switches-two switches for each odd/even input pair. One switch drops its corresponding input pair into mono. The second switch gives a +6 dB gain boost to its input pair, useful if the gain structure in your DAW is not ideal and you need a little more "boost over the top." In such a case, the boosts allow you to leave your internal digital faders at their optimum unity setting and use the gain boost in the analog domain, where there is plenty of headroom inside the Dangerous 2-BUS. Missing on the 2-BUS is a monitor volume pot and a headphone output, two features that would be useful if you don't have an external monitoring system available (like Dangerous Music's Dangerous Monitor). The rear panel is well laid out. There are sixteen XLR inputs, a Main output pair, and an isolated mult of that pair to be used as a feed to any external monitoring device. There is also a multi-pin connector for chaining additional Dangerous 2-BUS devices if you need more than sixteen inputs. The 2-BUS includes a separate, heavy-duty power supply that's almost the size of some analog console supplies. Connecting the 2-BUS is very straightforward, and the manual goes into great detail about the possible grounding and balancing issues one might encounter.
I've been fortunate over the years to have mixed on many different analog consoles, all with their own character. When the 2-BUS arrived, I was working with new artist Peter Walker on a project at Cello Studios in Los Angeles. Over the years, it's been home to artists like Rage Against the Machine, Elton John, Tom Petty, The Beach Boys and even Frank Sinatra. It's a true analog studio with a wide range of consoles: Neve, SSL, API and even Amek. The project I've been doing with Peter Walker is acoustic-based rock music. It was recorded to Pro Tools HD at 24-bit/48k. The tracks were cut on a Neve 8078, with bass and vocals recorded thru Neve 1073 preamps. Needless to say, things were pretty full sounding with lots of color. This project lent itself well to my controlled listening and comparison tests.
I started out by setting up an internal mix in my DAW of a song with a straightforward line-up: ten tracks of drums, an electric bass, electric and acoustic guitars, and a lead vocal. I spent some time balancing my mix internally in Pro Tools. No EQ, no plug-ins-just a very good balance. Monitoring was done on a variety of speakers: ProAc Model 100; Yamaha NS10M; and the studio's large, custom JBL mains. A number of tracks were hard-panned left and right, but a few were panned at various spots across the stereo field. For the first mix, all tracks were bussed out of Pro Tools outputs 1-2. Once I achieved my balance, I printed the mix at a healthy overall level to DAT.
I then put "O" VU calibration tones (1 kHz, 15 kHz, 50 Hz) into every fader inside the DAW and noted the gain setting for each track, watching the console's external VU meters. Next, I reset my bussing in Pro Tools to sixteen outputs. I took great care to make sure all my fader levels and pan positions were exactly the same. I then verified all this by placing the same tones thru Pro Tools in record-input mode and out through the Dangerous 2-BUS. Sure enough, all the track levels matched up exactly. The only oddity is that the Master Gain control on the Dangerous 2-BUS needs to be set at +6 dB to yield a unity in and out setting. (It states this in the manual I didn't read!) I listened carefully to the song through the Dangerous 2-BUS to make sure that all panning, track assigns, and balances were correct. I then printed this second mix to the same DAT.
My next step was to write all these settings down, including the panning, which I measured as an L/R gain difference. I reset all my faders in Pro Tools for unity gain and assigned them to sixteen individual outputs. I then sent the same tones to individual faders on an SSL 9000J console. After setting all my gains in the analog world, I now had the exact same mix on the SSL that I had created internally in my DAW. A thorough listening ensured me that the balances and pans in the SSL mix were the same as the DAW mix. I printed this third mix to DAT as well. I won't bore you with further details, but I printed a fourth mix through a vintage (but healthy) twenty-input Neve 8066 console fitted with 1066 and 1073 preamps. Throughout the testing, I used the same Pro Tools rig and DAT machine, moving them from room to room.
Okay, now the listening tests. Yes, I know you're all saying, "Why did you print to a 16-bit/44k DAT?" Sorry, it was just convenience. However, keep in mind that the listening tests were all relative to each other; and I did make some good mental notes while I was printing the mixes, before experiencing the digital crunch of the DAT.
The mix in Pro Tools was very good. The tones of the instruments were what I heard when I tracked the song through the Neve 8078. The Guild Starfire Bass with the flat-wound strings sounded just as thuddy as I remember. The drums were a little scratchy on top but just what I would expect them to sound like in this internal mixing environment. The new Pro Tools HD internal mixer is a major improvement over the previous Mix Plus TDM mixer, both in audio accuracy and in headroom. Overall, I was quite happy with the way my internal mix sounded.
Next, I listened to the Dangerous 2-BUS mix. Quite a difference. All the instruments sounded much more "outside the speakers," with more detail and a fine sense of transients. I could almost tell the exact thickness of the pick that was used on the acoustic guitar. The overall stereo image sounded wider and the low end seemed extended compared to the PT internal mix. However, at times I got the feeling that the mix was almost too transparent, perhaps even a bit scooped in the lower mids. My flat-wound bass guitar didn't quite have the character it had in the internal mix. But wow, my cymbal sound was back, and my vocal had lots of air and clarity.
I now listened to the SSL 9000J mix. This is a familiar tone. Recently, I've been doing most of my mixes thru 9000 consoles. I'm very fond of their open character as well as their warm bass response. The mix sounded great, with lots of personality. The character of my bass guitar was back, but overall I was missing some of the detail and clarity that I heard through the Dangerous 2-BUS. The top end almost seemed a bit muted-obviously the difference between the simple path of two high-speed chips in the Dangerous 2-BUS vs. lots of analog circuitry in a large- frame analog console.
Next was the Neve 8066. This was another sound all together. My mix had bottom and warmth like a 1970 Neil Young LP. However, things seemed a bit soft and slow compared to the SSL and Pro Tools. But what tone and
character! My lead vocal sounded huge and warm with lots of chest tone. A very compelling sound. On the other hand, the drums were thick and tonal but certainly not as fast and dynamic as they were through the SSL or the Dangerous 2-BUS.
My conclusion? Everything has its own sound. The PT mix was just fine sounding. It was a very good representation of my tracks. The SSL and Neve consoles have their own colors that they added to the tracks. The Dangerous 2-BUS is fast and open, has lots of stereo width, and is super high-fidelity. It's a great alternative if you can't afford a six-figure mixing console, and the internal DSP mixer is not accurate enough for you. It provides a noticeable improvement in fidelity. But then again, if you prefer vintage gear for its sound, the 2-BUS might not have enough of a sound of its own. On the other hand, if you're a DAW user who prefers honesty and a straight-wire approach, consider adding the 2-BUS to your setup. ($2,999 MSRP; www.dangerousmusic.com)