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Solid State Logic Sigma: 16-Channel SuperAnalogue RackMixer for Your DAW

Solid State Logic’s Sigma Summing Engine is a remote-controllable 16-channel analog summing engine with a monitor section. It uses the same SuperAnalogue technology as SSL’s Duality and AWS consoles, accepting 16 stereo channels of line-level audio from any DAW I/O unit(s) over Tascam standard AES59 25-pin D-sub connectors—four stereo pairs per DB25 cable. No other hardware is required for basic summing of 16 stereo pairs to a stereo mix bus plus monitoring.

Sigma can be run wirelessly via tablet or Smartphone, or wire controlled through your computer’s Ethernet port.

Solid State Logic’s Sigma Summing Engine is a remote-controllable 16-channel analog summing engine with a monitor section. It uses the same SuperAnalogue technology as SSL’s Duality and AWS consoles, accepting 16 stereo channels of line-level audio from any DAW I/O unit(s) over Tascam standard AES59 25-pin D-sub connectors—four stereo pairs per DB25 cable. No other hardware is required for basic summing of 16 stereo pairs to a stereo mix bus plus monitoring.

Front and Back

The thick, sculpted aluminum front panel of Sigma frames a large number of individual color changing OLEDs mounted behind it showing input level metering for all 16 channels, plus a larger, high-­resolution stereo master meter. Each of the 16 channels can be configured as a stereo or mono source—but you cannot split a single stereo channel into two mono channels.

The green channel number LEDs light up to show channel(s) that are programmed to use the left side of a stereo source as mono. There are indicators for the individual channel assignments to either Mix Bus A (orange) or Mix Bus B (red). Any channel can connect to both Mix A and Mix B at the same time or none at all—for use of each channel’s direct output only.

Other features include two user-programmable buttons, a 1/8-inch mini-jack for connecting a mobile player as a monitor source, ¼-inch stereo headphone jack, and power on/off switch. A blue knob rotary encoder selects (via its push function) front panel local control for: control room monitor, headphone, and both Mix Bus A and B master fader levels.

Sigma’s back panel has 16 stereo/mono inputs and 16 direct outputs using eight D-subs. Two more DB25s provide connections for Mix A and B bus insert send/returns, a stereo headphone output with volume control, and two external stereo source inputs.

Sigma’s monitoring section has three pairs of analog line level L/R, XLR outputs for Mix A, Main and Alternate monitor. The rear panel offers a 12-volt DC inlet jack for the line lump power supply. There is a programmable footswitch jack, an RJ45 Ethernet socket, and USB socket/switch for SSL diagnostic use.

Sigma Setup

Although you can use any analog I/O with Sigma, I opted to run Pro Tools 11 using Solid State Logic’s MADI system. I installed the MADIXtreme 64 PCIe interface card and its driver (version 1.3) into my MacTel 8-core running OS 10.8.5 and Pro Tools 11 HD and was good to go for up to 64 channels of simultaneous input/output audio at 44.1 or 48 kHz, or 32 channels for 88.2 /96 kHz, all running Core Audio. (Host based—no Avid card or interfaces.)

I used a 3-meter twin glass multimode 50 /125μ fiber optic cable (about $60) to connect to and from the MADIXtreme card to an SSL XLogic Alpha-Link MX 4-16 DAW I/O ($1,699 bundled with the MADIXtreme PCIe card), which was then fiber-looped to a second MX 4-16 ($1,449). The two MX 4-16s and MADIXtreme 64 card provide a total of eight analog inputs and 32 analog outputs at a total cost of $3,148.

I then installed ipMIDI software (version 1.6)—a utility that shows up in Audio MIDI setup app in Mac OS X. Next I connected a NetGear GS105 5-port Gigabit switch between my Wi-Fi router, Sigma, my SSL X-Patch and my computer.

You can also directly connect to your computer’s Ethernet port (fixed IP), but you’d lose wireless operation and any connectivity to the Internet. After powering up and launching Safari, Sigma’s browser GUI was available and ready for use.

For wireless control using my iPhone and iPad, I connected via the Mac’s Bonjour feature. The Sigma User Guide walks you through many networking configurations using either a fixed IP address or a DHCP, and controlling Sigma on Wi-Fi-connected devices.

Browsing Sigma

Sigma’s browser GUI has three main pages. The default Master page has buttons and drop-down menus for meter source switching, master insert routing—including an insert sum function to connect a second Sigma—headphone source and level, footswitch setup and designating the function(s) of the two front-panel pushbuttons. There is a MIDI Learn feature for generic MIDI controller programming for specific changes such as Mix Inserts in/out.

The Channels page mimics Sigma’s front panel but with fader levels indicated in dB and all channel names. It has buttons for global setup and solo modes, plus 16 Mono buttons for changing any channel to mono. A pan pot will pop up for panning the new mono channel across the stereo bus(s). There are solo and cut buttons for each channel.

The Settings page has the DAW/Protocol and ipMIDI Port/Channel, IP address shown (fixed or DHCP), Meter scaling, solo modes (SIP/AFL, Latch/Alt) and software version and update button.

Configuration/setups created in the browser can be named, modified and saved as .xml files, with the last setup reloaded at start-up. When you save in the browser window, it always defaults to: “SigmaSettings.xml”—it does not track the given name of your last save—you’ll have to retype it every time and replace the old one. I saved and named (by song or artist) setups for both mixing and tracking sessions.

After connecting 32 stereo analog sources from the Alpha-Link interfaces, I set the global operating levels for +24 dBu via the browser. Mix A and Mix B buses have separate stereo inserts and (normally) sum together—with Mix B able to be routed pre/post Mix A. You could have all your vocal tracks on Mix A and all your instruments on Mix B for different stereo insert processing on each, and then combine them—relative to their individual master fader settings.

Workflow Explained

Mixing and recording using Sigma requires organization and forethought to maximize its potential and the good use of its console center section monitoring. However, with so many routing and monitoring scenarios possible via this unit’s extensive I/O, I would recommend using a well-labeled, external patch bay. Besides using it as a static summing amp and sending mix-leveled stems to Sigma for analog summing, there are two methods for sending fader-level automation data: HUI/MCU and MIDI Absolute (mutes are not supported).

HUI/MCU protocol in Pro Tools designates the first 16 faders in your mix must be audio tracks and uses ipMIDI ports 1 and 2 set in Pro Tools’ Peripherals/MIDI Controllers page. Sigma’s MIDI Absolute mode designates ipMIDI Port 9 and channels 1 through 16 to control the Sigma. MIDI controller faders in Pro Tools use up no voices and can be located anywhere in the mixer and freely assigned (individually) to any Sigma channel.

I preferred MIDI Absolute, and I got into the habit of naming the 16 MIDI faders by what they control and locating them near the track/buses they control. In addition, I copied the stem bus names used in PT back in Sigma’s browser window. HUI/MCU mode automatically sends the names from the first 16 faders to Sigma’s screen but MIDI Absolute does not.

I like to record and playlist all mix passes into a new stereo audio track in Pro Tools, so I routed Sigma’s Main Mix A output to the first two inputs of the first Alpha-Link MX 4-16. The mix’s return used Sigma’s last stereo output channel 16, and I deselected both Mix A and Mix B buttons—to prevent a feedback loop. Inputs 3-4 of the first MX 4-16 I reserve for last-minute overdubs during the mix.

For monitoring, I connected channel 16’s direct outputs to the L/R stereo External Input of Sigma via the rear panel DB25s. I selected External for the monitor source and controlled main monitor, alt monitor and headphone volumes with the rotary controller.

Sigma’s Mon L and Mon R XLR outputs connected directly to my powered monitors, and the Alt L and R go to the amp that powers my Yamaha NS-10M speakers. Back in Pro Tools, I solo isolated the mix track and locked it to Input monitoring while developing a mix.

Is Sigma for You?

My Sigma review rig provided a tremendous amount of detail, stereo width and space without audible noise. Patching external compressors and/or equalizers between the Alpha-Link’s outputs and Sigma worked well. Because I used both Mix A and B buses all the time, I usually put the backing track on Mix A and the vocal production on Mix B. I also reserved channel 15 for routing all stereo effect returns generated in Pro Tools. In Sum mode, Mix A and B inserts sum the insert return with the original main stereo mix bus signal and work excellently for separate processing of the track and vocals.

I performed my automation moves either on my Pro Tools screen with a mouse, or by using my PreSonus FaderPort motor fader. I liked the monitoring facilities built into Sigma, especially when going wireless from my iPad or iPhone. That way I can walk around the room and change volume on the monitors as I like.

Sigma is a step up from typical in-the-box mixing. I’m getting everything I love about mixing music on large and expensive analog consoles without any down side. I have the dynamic sound of analog summing—combined with modern automation and ease of mixing in the box. What could be better?

Barry Rudolph is an LA-based recording engineer.

Product Summary

COMPANY: Solid State Logic.

PRODUCT: Sigma Summing Engine

PRICE: $4,500

PROS: Awesome analog summed sound.

CONS: Serious configuration required.


Sigma’s Mix Bus B can be injected into Mix A by engaging the “B To A” button in the web browser. I used this function to get some additional mix bus coloration by turning up Mix B’s master fader above 0 dB (it goes up to +10 dB) and turning down Mix A’s master fader. This is an intense sound that does not sacrifice brightness and clarity for the sake of loudness.