Exploring the SSL Origin's Listen Mic Circuit
- Pat Wright
- Jun 16
- 4 min read
Updated: Jul 3
At L&M Pro, we’re constantly looking for creative ways to explore the capabilities of the gear we use and love. Today, we’re diving into a particularly interesting feature of the SSL Origin console: the Listen Mic circuit — a fixed-parameter compressor circuit best known for its accidental but iconic use in recordings such as Peter Gabriel’s “Intruder.”
Whether you're an engineer working on a modern SSL Origin or a gear enthusiast fascinated by studio history, this article offers a detailed breakdown of how the circuit works, how we tested it, and the results we achieved using both close and room miking techniques.
What Is the Listen Mic?
The Listen Mic is a talkback microphone circuit that was originally designed for internal studio communication. The configuration consists of two inputs:
A direct mic input (low-Z), supporting dynamic or condenser microphones with an onboard 48V phantom power option and a trim pot adjustable via a small screwdriver.
A post-mic pre line-level input, accessible VIA DB25 connectors, designed to interface directly with the console’s mic pres.
These two paths join just before entering a fixed compressor, the Listen Mic Compressor. Importantly, this compressor cannot be adjusted from the surface panel. All of the parameters are completely fixed internally, tailored to ensure consistent levels from voices at varying distances, compensating for proximity and preventing overload.
Signal Routing
As shown in the console’s block diagram, the output of this circuit can be routed to various locations via the communications section. For the purpose of our tests, we routed the signal via the “Listen Out” line located on the “F/B Misc Out” DSub connector.
To simplify future experimentation, we patched this output into our studio’s patch bay, making it quick and convenient to route the Listen Mic signal to different destinations for creative or testing purposes.
Testing Methodology
We conducted two primary tests to explore how this circuit behaves when subjected to real-world audio sources — specifically the snare drum. Our goal was to evaluate the tonal characteristics imparted by the compressor in both close and ambient mic positions.
Test #1: Close-Miking the Snare Drum
For this test, we connected a Shure SM57 to a Neumann V 402 mic preamp. The microphone was placed just above the rim of the snare, angled toward the center.
A key observation emerged during setup: if the V 402’s gain wasn’t high enough, the signal didn’t cross the compressor’s threshold, and the effect was minimal. However, once we increased the preamp gain to a more aggressive level, the compressor began to engage — and the character of the sound changed dramatically.
Signal Flow
We used our patch bay in two modes, isolated and half-normalled mode. This allowed us to split the mic pre output, sending one signal to the Listen Mic circuit (isolated) and simultaneously printing a dry (uncompressed) version. This dual-path method ensured phase coherence and gave us the flexibility to blend signals during mixdown if desired.
Test #2: Room Mic in Omni Mode
Next, we replicated the signal flow from Test #1, but substituted the SM57 with a Neumann U87, placed in the center of our showroom and set to omnidirectional mode. The goal was to simulate a drum room mic in a live space.
Again, we adjusted the mic preamp gain to ensure the signal met the compressor’s threshold. This allowed us to evaluate how the Listen Mic would behave with ambient audio — a situation closer to its original purpose.
Observations and Results
Close Mic – SM57 + Neumann V 402
The Neumann mic preamp is a great mic pre! And, produced a highly favorable full, punchy warm tone with pleasing highs.
Once engaged, the Listen Mic’s compressor darkened the snare tone, extended the decay, and softened the initial transient.
The result was musically pleasing, if somewhat stylized.
Importantly, the ability to print both compressed and dry versions — in phase — offered mixing flexibility and underscored the value of capturing both signals simultaneously.
Room Mic – U87 in Omni
While our showroom is not acoustically treated like a traditional live drum room with treated and natural wooden surfaces, we still noted meaningful results:
The dry recording sounded as expected for a mic placed in a large, untreated reflective room.
The Listen Mic circuit, however, introduced a distinct compression effect — really clamping down on initial envelope and breathing with the signal's release.
The end result had an engaging sense of movement and energy — the “crush” effect long associated with this circuit was clearly evident.
Given a better-sounding live room, we believe this method could produce even more impressive results, not just on drums but potentially on other instruments or sources where room character and compression interplay creatively.
Conclusion
The Listen Mic circuit on the SSL Origin console is more than just a communications utility — it’s a unique creative tool that can deliver distinctive tonal shaping through its fixed and unique compression circuit. Our tests confirm its value when approached thoughtfully, whether as a parallel effect, a blendable element, or simply a creative experiment.
If you own an SSL Origin and haven’t explored the Listen Mic for audio capture, we encourage you to patch it into your workflow and experiment — you might be pleasantly surprised by what you hear.
– L&M Pro Thanks for reading, and happy recording!
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