Solid State Logic Duende

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SSL's consoles have been the stalwart centerpiece of many an A-list recording studio for decades, and for good reason. The sound of the EQ and compression circuitry is like no other, and to many it is synonymous with major-league recording. Until recently, the legendary SSL sound was primarily reserved for those with serious budgets. But SSL has changed all that, bringing its sound within reach of every desktop computer musician. The Duende line of accelerator hardware and plug-ins brings the SSL sound to VST, RTAS, and Audio Units–format plug-ins for Windows XP and Mac OS X.

The Duende product line comes in three flavors: Classic ($1,875 MSRP), Mini ($995), and PCIe ($1,495). Classic and Mini are external FireWire boxes, while PCIe is the internal card version. Each unit contains four SHARC processors for handling the serious computational requirements of SSL''s algorithms. The Duende Classic and PCIe can handle 32 mono instances of plug-ins at 44.1 or 48 kHz (or 16 instances at 88.2/96 kHz), while the Mini is initially configured to run half that amount. A paid upgrade ($399) unlocks the same amount of processing power in the Mini as its big brothers.

The algorithms used inside Duende have been taken (and improved upon) from its C-series digital consoles, which, in turn, were based on the sound of its famous 9000- and 4000-series analog consoles. Duende Classic and PCIe both come with the EQ and Dynamics Channel Strip and Bus Compressor plug-ins, while the Mini includes just the Channel Strip. The Bus Compressor can be purchased for the Mini as an add-on ($399). SSL has created three additional plug-ins to expand the Duende''s capabilities: Drum Strip ($399), X-Comp ($499), and X-EQ ($599, which I will discuss in a moment).

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Duende''s EQ and Dynamics Channel Strip plug-in is a replica of the EQ and dynamics portions of an SSL 9000 channel (see Fig. 1). It features enough tone-shaping capability to polish and improve any conceivable type of sound. The filter section has high- and low-pass filters, which are routable to either the compressor sidechain or the audio output. The EQ section features high- and low-shelving bands and two variable Q parametric bands. The EQ can be configured to either type E or type G (see below), and can be routed to the dynamics sidechain or output, as well. The dynamics section offers both a compressor with automatic make-up gain and an expander/gate with a Hold control. Dynamics can be set before or after EQ in the signal chain. The input control section includes a phase-reverse button, and the output has a sidechain listen mode so you can hear which frequencies are driving the dynamics section.

Duende models both of SSL''s EQ curves: type E and type G. The plug-in defaults to the G setting, but you can switch to E by pressing the “E” button in the equalizer section. The G algorithm varies the bandwidth, or Q setting, depending on the amount of boost or cut you have applied. The E algorithm uses a fixed amount of Q, regardless of the gain amount. At maximum boost or cut, the EQ curves are the same but they follow a different curve to get there.

One could generally say that the G curve is more gentle and “musical,” while the E curve is more surgical and aggressive. You can create a sharper band of EQ at lower gain levels with type E, which makes it more suitable for corrective applications. The changing Q setting of type G gives it a relatively broader, gentler curve at low settings, which is often better for subtle timbral shaping of voice and instruments. I personally find myself using G-type EQ more often than E for my musical mixing tasks, but it is great to be able to A/B the two options while sculpting my sound. For postproduction or sound-design tasks, I think that the E curve is frequently the more appropriate choice.

I have always preferred the feel of a real knob to operating mouse-driven knobs within software. But SSL has included a nifty feature to make operating the virtual knobs more tactile: If you mouse over a knob onscreen, then it will respond to the mouse wheel just as if you were turning it. No clicking the knob and dragging required; moving the wheel up turns the knob to the right, and moving it down turns it left. It takes about two full moves of the scroll wheel to move the knob its entire throw, which seems like a good compromise between fine control and too much finger movement. Mix Glue: The SSL Bus Compressor Track compression is a critical tool in evening out the dynamic inconsistencies of individual instruments. Similarly, bus compression can be used across an entire mix (or a complex series of sounds working together, such as drums) to tame peaks and bring up the overall level of the song. The Bus Compressor, first introduced in the master section of the SSL 4000-series consoles, is legendary for adding punch while smoothing out the peaks to allow for higher gain. SSL has replicated the design of its 4000-series bus compressor in the XLogic G Series analog compressor and in Duende''s Bus Compressor plug-in.

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The Bus Compressor plug-in (see Fig. 2) has a few significant differences from the compressor in Channel Strip. To start with, there is a dedicated make-up gain control, as opposed to Channel Strip''s automatic make-up gain. This is to allow for fine-tuning of levels at the final mix stage. It has five choices of attack time to fit with different styles of music, as opposed to the auto- or fast settings of the Channel Strip. There are four fixed release times, as well as an Auto setting that is dependent on peak signal duration. Finally, it has a nice, big analog-style VU meter to give an accurate reading of the amount of gain reduction.


Since I''ve begun working with this system, I''ve consistently found that Duende''s channel strip and bus compression plug-ins have brought “the sound of rock” to my Pro Tools–based tracks. Using Channel Strip, I''ve frequently found myself adding shocking amounts of EQ to a track, often without even realizing it. Gain boosts that would make most other plug-ins sound shrill or harsh sound big and full with Channel Strip. The interface is quite simple, and once you really learn it the mix process just zips along.

I recently remixed a cover version of AC/DC''s “Back in Black” using all Duende plug-ins. I made the slashing rhythm guitars sound like a tornado by applying generous helpings of compression and mid-range EQ. I re-sculpted the kick drum''s shape by using the Channel Strip compressor, sharpening the attack while adding enough low-end beef via EQ to shake the room. Adding some high-end air and a moderate amount of compression to the lead vocal made it as clear as a bell within the mix, occupying a solid center in the eye of the storm without having to use loads of gain. Finally, strapping the Bus Compressor across the master bus gave the whole song a smooth cohesion while increasing the perceived loudness significantly.

I''ve really noticed the same effect with other rock tracks I''ve mixed since getting Duende—everything seems to sound bigger, beefier, and more like the classic rock albums I''ve grown up listening to. For further reading on the topics of usage of EQ and compression to improve your mix, go to and check out the Duende tutorial section, or go to for lots of information on the art of recording and mixing.

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DAWs are terrific tools, but they are not the only way to work. Many people like the immediacy and convenience of tracking to and mixing from dedicated hard-disk recording systems. Others like the classic sound and feel of using analog tape recorders. If you have a DAW and a preferred playback recorder, then you are in luck. You can use your DAW to build a virtual SSL console with Duende, running the signal out of your recording device and into your DAW, and then back out again to a 2-track recorder (or you can simply record the mix to an audio track within your DAW), without ever actually recording or transferring your multitrack audio into the DAW. Using this technique, your DAW is processing the incoming signal in real time, much as a mixing console does. I like to call this “mixing through the box.”

For our example, let''s say that you have an 8-track analog recorder and a 2-track mixdown recorder. To mix through the box, connect the outputs of your recording device into inputs 1-8 of your DAW''s I/O. Next, create a project or session in your DAW at 96kHz, 24-bit resolution (or 48kHz, 24-bit if you are using the unexpanded Duende Mini). Create eight auxiliary inputs (not audio tracks) and a stereo master track. Now create an instance of Duende Channel Strip on each of the aux tracks and then strap a stereo instance of the Bus Compressor plug-in across the master bus (see Fig. 3).

Start playback on your recorder and begin adjusting track EQ and compression within Channel Strip, and set gain using the DAW''s faders. Use the Bus Compressor on the master bus to create a cohesive, bigger-than-life sound. Route the stereo signal to your 2-track recorder, making final adjustments with the bus compressor''s makeup gain or the master fader''s level to get optimal gain structure. You can add reverb or other processing to the mix by creating additional aux tracks fed by sends from your input tracks. Congratulations—you are mixing on an SSL console! For added fun, throw a MIDI controller in for tactile control of levels and EQ/compression settings. For me, there is an immediacy about working this way that is a refreshing change from the standard DAW paradigm.


Plug-in latency is an unavoidable aspect of host-based processing systems, even with plug-in accelerators like Duende. These days, most DAWs have delay-compensation features to keep your tracks in sync. If you are using a system that doesn''t have this feature, Duende offers a workaround. Simply run an instance of Channel Strip across every track or bus. This will ensure that all tracks are delayed by the exact same amount of time.

If you don''t need Channel Strip for a particular track or bus, engage the Bypass All button within Duende''s interface (not your DAW''s plug-in Bypass button). This will disengage any processing of your audio while maintaining the same amount of delay as tracks that are actively using Channel Strip.


If four SHARCs are not enough processing horsepower for you, you can expand your system to two units. Any combination of Duende Classic, Mini, and PCIe will work.

As I like to work at 96kHz, 24-bit resolution, a pair of Duendes would give me a good-sized virtual mixing console: 28 input channels, along with a bus compressor for the drum group and another bus compressor for the master output. Or perhaps a 24-channel console with the same bus compression, plus a pair of channel strips on the master and a pair for the main reverb return. And needless to say, if you work at 44.1 or 48 kHz, a pair of Duendes will build you a hefty mixer indeed.


Though Channel Strip and Bus Compressor are the meat and potatoes of any mixing situation, SSL has been creating additional plug-ins to expand Duende''s capabilities.

Drumstrip. Drumstrip is a stereo plug-in specifically oriented toward shaping drum tracks. It features a sophisticated gate, a transient shaper, high- and low-frequency harmonic enhancement, and the listen-mic compressor that created the famous gated drum sound of the '80s.

Each of the functions has its own bypass switch. This makes it easy for you to concentrate on a single process at a time, and then try them together to see how they work toward creating an overall sound. The high-frequency enhancer is great for bringing out definition in drums, while the low-frequency version works well in adding weight and power to the sound.

X-EQ. As a ten-band mastering-grade parametric EQ designed for the highest-caliber signal processing, X-EQ features a real-time spectral analysis display, high-resolution input and output metering, six bands of parametric EQ that can be set to nine different EQ curves, low- and high-shelving EQ, and lowpass and highpass filters with five different filter types each.

The plug-in offers two processing modes: serial and parallel. The serial mode is the more common, traditional approach to parametric EQ design, where the signal flows from one band into another. In the parallel mode, the signal flows through the pass and shelving filters serially, but then enter all six parametric bands in parallel. Some famous vintage passive equalizers used this approach in their design, and the result is a markedly different sonic signature than the serial mode.

X-Comp. X-Comp is a versatile mastering-grade compressor with all the conceivable bells and whistles. It includes a dual-knee control for creating complex compression curves, a maximum gain-reduction control, sophisticated metering and gain-reduction graphs, and a frequency-dependent pass-through control. Both X-Comp and X-EQ come with a series of musically useful presets that you can use to get started with.


I had a rather challenging mixing task that turned out very well when using Duende''s plug-ins in tandem. I had to take a kick drum track recorded in the '70s and remix it for use in a modern project. The problem was that there was tons of electric guitar bleed in the kick mic, which could not be audible in the finished track.

I started by using Channel Strip''s downward expander to create a greater dynamic separation between the kick and the guitar material around it. I used the expander gently with the fast attack setting so that the attack and release characteristics of the kick were not affected at this stage.

Next, I used X-EQ''s shelving and parametric bands to create fairly steep filtering, which rolled off the majority of the guitar sound in the signal. Unfortunately, it also removed the beater click portion of the kick drum. I used X-EQ''s Analyze function to help visualize and locate much of the guitar''s frequency range, which made it easy to remove it without losing more of the kick drum than necessary.

Next up came Drumstrip. I used its Gate function to remove the offending noise between kick drum hits. This was made easier by the fact that Channel Strip''s expander had already increased the track''s signal-to-noise ratio. It still took a bit of fine-tuning to make the track sound natural and to ensure that all quiet kicks were heard. Now I had a good low-frequency kick-drum sound, but there was no beater to cut through the mix. Liberal use of Drumstrip''s high-frequency enhancer solved this problem, deriving new upper-harmonics from the existing kick-drum sound. I also added a touch of the low-frequency enhancer to blend in a bit of gut-rumbling lows that were not feasible when this track was originally recorded for LP. For the final icing on the cake, I called up the “Punchy BD” preset in X-Comp. This patch further enhanced the sound of the beater click and tightened up the amplitude envelope a bit more.

Once I came up with a working process, I applied it to kick and snare tracks from another song, fine-tuning the parameters to their needs with similar excellent results. Though I''m a big fan of analog hardware, I couldn''t imagine coming up with this type of solution outside of the digital domain. The flexibility of using specific aspects of each of these plug-ins with each other made for an elegant solution to a thorny audio problem.


Duende isn''t about endless bells and whistles, which is why I like it. The Channel Strip and Bus Compressor plug-ins have enough control to sculpt your sound effectively without getting caught in knob-twiddling minutiae, though if it is fine-grained control you need, then Drumstrip, X-EQ, and X-Comp are terrific. Duende delivers the big, punchy, larger-than-life sound that can be hard to find in the world of plug-ins.

The fact that SSL has now made its famous sound available to everyone for less than $1,000 marks the company's serious entry into the entire project studio market. If you are looking for a way to take your mixes to another level, then Duende is a rock-solid choice.


SSL Duende Classic, Mini, and PCIe