Building a Pristine Live Sound Preamp—Under the Hood of VENUE | S6L

By in Live Sound, Music Creation, Tech Talk

VENUE | S6L is much more than Avid’s latest live sound console. It’s actually a completely new live sound platform—and Avid’s largest live sound project to date. Although the S6L is built on VENUE software and its associated workflows, the system’s hardware has been developed from the ground up.

There are two key areas of development Avid’s engineers wanted to achieve. One is that the system would support the highest possible sample rates for both mixing and recording. And two, further improve the signal chain from input to output to deliver the best sound quality possible.

VENUE systems have been highly regarded for their pristine sound quality for over 10 years. And their uncolored sonic profile is the perfect complement for the huge assortment of onboard plug-ins available to engineers to tweak and enhance their mixes. With the S6L project, our engineers relished the challenge of updating VENUE’s sound quality even further, using the latest technologies and components available, while still maintaining the sonic flexibility that VENUE systems are known for.

VENUE consoles are designed for transparency. Before VENUE, I had spent 25 years shrouded in analog, where every component texturized what I wanted to do. When I moved to VENUE, I was able to finally go to the very depths of what I had dreamed of, certain sounds, and explore to find them—and the console never got in the way. I was so free, I was giddy!”

– Greg Price, FOH engineer for Ozzy Osbourne, Black Sabbath, Van Halen

A key piece of the puzzle was to design a new preamp for the system. One that would deliver uncompromising performance, with unerring accuracy, and support up to 192 kHz operation. Avid’s philosophy is to offer the most accurate sound possible in order to provide engineers with the greatest flexibility and sonic palette.

If a preamp imparts a strong sonic signature, you can never uncolor it—you are stuck with the preamp’s innate sound regardless of what you may want to do with the signal afterwards. Preamp coloration that works for some sound sources may not be ideal for others, and most live sound engineers mix a variety of artists and genres and should have the flexibility to add their creativity to the mix without being painted into a corner because of a baked-in sound.

“The style and topology of modern preamp designs for digital consoles requires us as mixers and engineers to think a little differently.”

— Robert Scovill

According to award-winning concert sound mixer Robert Scovill,  also a senior specialist for live sound products at Avid, “The style and topology of modern preamp designs for digital consoles requires us as mixers and engineers to think a little differently, and in turn, set different expectations for what we want to achieve at that point of the signal chain. With ‘one-trick pony’ preamp designs that have their own signature sound, you really have to tailor your preamp choices in order to truly do justice to the sound of each source. This is all fine for studio tracking workflows where time may allow you to optimize the pre choice for each source and song, but that approach is wildly impractical for the live sound workflow. It’s simply why I love our approach of offering ultra-high quality and accuracy that results in a completely transparent pre design, and all accomplished just before the digital conversion. Once converted, the choices of character and color refinement can then easily be changed at will—even on a per song, or per sound basis if we desire to do so. That is beyond empowering with regard to creativity.”

Robert mixing FOH for Tom Petty & the Heartbreakers

As long as I’ve chosen the correct mic and the correct position, then what I hear with VENUE matches very closely to what I’m looking at on stage, and that is exactly what I’m looking for. I then have the choice to color the signal in any direction I choose, be it warmer or grungier, without being hampered by preamp coloration.”

– Chris Madden, FOH engineer for Pink, Sade, Jessie J.

Chris mixing FOH for Sade

Designing a preamplifier circuit is a mix of art and science. From the beginning, the team’s goals were to make it as clean as possible, with a wide dynamic range, low distortion, a great signal-to-noise ratio, and sample rate support of up to 192 kHz—while minimizing delay through the audio chain. To achieve this, the team decided early on to use a microcontroller to control the mic pre gains for superior performance. After significant research, they chose the 5173 digital gain controller from THAT Corporation. THAT Corporation is an audio engineering company focused on creating high-performance analog components for professional audio applications. Some notable customers include Apogee, Benchmark, and Great River.

The 5173 is a very robust digital gain controller (IC) that operates at larger voltage rails, so it’s more forgiving and requires less circuitry that can compromise audio performance. One of the advantages that the 5173 provides when used in conjunction with Avid’s special hardware around the IC, is that when it applies gain changes, it dezippers in a nice, deterministic manner to ensure the lowest possible switching noise and provides smooth gain changes in 1 dB steps. Even with its compelling performance specs, the 5173 offers substantial power savings over many competitive IC solutions—a significant benefit, given that the S6L’s Stage 64 I/O rack supports 64 total inputs, an improvement over the 48 inputs offered by our previous generation Stage Rack.

The 5173 digital gain controller mates with THAT’s 1580 low-noise differential audio preamplifier IC. In contrast to alternative solutions that offer all-in-one ICs, THAT Corporation splits its controller and preamp components into separate ICs. This not only gives manufacturers like Avid greater design flexibility to mix and match optimal componentry, but—more importantly—it optimizes the ICs by fabricating the digital gain controller section in a high-voltage CMOS process. And coupled with the 1580 analog preamp, which was designed from the ground up in a BiCMOS process, together they deliver lower noise and higher performance, offering the best of both worlds—a unique approach in high-end pro audio. So while competitive offerings have limited input voltage capability, S6L’s preamp offers a gain range of 10–60 dB and is optimized for an input impedance of 4K—regardless of whether the input pad is on or off. This means it is possible to passively split an incoming microphone signal to several consoles without degrading the signal.

THAT 1580 low-noise differential preamplifier IC

The team also applied their collective experience in optimizing S6L’s preamp design even further, utilizing careful layout characteristics. This includes thin film resistors to minimize Johnson noise (which ultimately causes higher distortion), and pristine power supplies to feed all of the analog circuitry for the most accurate performance.

The result? The team significantly exceeded the target specs, testing all the way up to 192 kHz operation. But perhaps FOH engineer Greg Price said it best when the team took S6L to a recent Van Halen sound check and he heard the preamps for the first time:

“Those inputs are sounding the way I’ve always dreamed of!”

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Sr. Marketing Manager for Avid Live Sound Systems and Music Notation. I previously worked at Euphonix and E-MU Systems before joining Avid.