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Sigma FAQ


Sigma Documents

The Sigma documents can be found here.


Sigma Delta Upgrade

All Sigma units can be upgraded to Sigma Delta units by purchasing the Sigma Delta Plugin.   The Delta plugin is SSL Part #: P990DCTLA and can be purchased from your local SSL Distributor.

If upgrading a unit running the V1 software and firmware it is necessary  to update to the first V2 firmware and sigma remote software before updating to the latest software.   Only units running the V2 firmware and software can use the delta plugins.


Sigma Update Using Internet Explorer 10

To update your Sigma software (to 10.3.6 at time of writing) please either update Internet Explorer to version 11, or use another browser such as the latest version of Chrome or Firefox.



Moving Sigma Settings from Web Browser to the Remote App

The web browser remains available in Sigma Delta V2 software.

Sigma settings stored in V1 software can be recalled via the web browser using the Load tab.

From there, you may manually enter and save the settings into the Remote App for further use.

Please note that Adobe Flash is now deprecated and may affect some web browser functions.


Sigma Setup Information

Sigma Control Methods

Sigma Delta can be controlled using a variety of methods, which can be combined to suit any workflow. These include Remote app, MCU hardware control surface, Delta Control plugin, and web browser.

Sigma’s analogue faders can receive control from a HUI or MCU enabled DAW, using the ipMIDI. This allows for fade and cut automation to be written in the workstation of choice, and saved with the project.

The Sigma Remote app controls the configuration of the Sigma hardware. Channel strips can be switched between mono and stereo mode, bus routing options can be set, and external processing equipment can be switched in to the insert points. These option can also be mapped to a MIDI controller, allowing you to take control using encoders and push buttons.

Sigma’s web browser interface can be easily accessed using a tablet or smartphone, providing touchscreen control over Sigma.

Finally, a footswitch jack is provided on the rear of the unit, which can be assigned to a variety of controls, including talkback.


Sigma δelta Updates

Sigma δelta (V2.0 software) was released early 2016. It is a software-only update for all Sigma devices. A minor update, V2.1 was released February 2017.

1. Delta Control plug-in

  • Sigma level and cut control from DAW plug-in

  • Use standard DAW automation features to control analog levels

  • Place plug-ins anywhere in DAW mixer

  • Single fader plugin or 16-fader plugin options.
  • AAX, VST2, VST3, and RTAS

2. MCU DAW control

  • Fader, cut, solo, and pan controls directly from a hardware MCU control surface

  • Mix A and Mix B assignments using control surface software key and Sel switch

  • Sigma channel names displayed on surface

  • Cut, TB, Dim, Mono, and Alt switches assigned to control surface soft keys

3. New macOS, Windows, and iOS apps

  • Greater speed and precision and easy to integrate control options

  • Improved GUI

  • Control Sigma volume from the app

  • Faster, more accurate replay of mix data

  • Transfer automation between Sigma, AWS, and Duality

Sigma Delta Software Upgrade Cost

The V2 software including App and Sigma software is free for all users

The Delta Plugin for Sigma must be an order placed through your local distributor or office.
The part number to use is P990DCTLA - DELTA PLUGIN CONTROLLER.

If you don’t need the Delta plug-in at this point you can still upgrade the Sigma software to v1.0.4.x to take advantage of the new Remote App, control surface compatibility and improved performance.


Summing Channel Capacity

The Sigma can sum up to 16 stereo channels, which can be assigned to two stereo buses: Mix A and Mix B.  Inputs can be configured as either mono or stereo paths. Where a stereo channel is sent to a Mix bus, the left input will be routed to the left channel of the Mix bus, and the right input will be routed to the right channel of the Mix bus.
Where a mono channel is routed to a Mix bus, the left input of the channel is sent to both left and right channels of the Mix bus, controlled by a pan control in the Sigma browser. The channel’s input meter will display signal on the left meter only, and the right input to the channel will be disconnected. To configure a channel in this mode, select the channel in the Sigma Browser and select the “Mono” button.


Multiple Sigma Devices

More than one Sigma can be cascaded on one system to achieve a higher channel count.

Up to four Sigmas on one DAW have been successfully tested.

Please see the Sigma Delta manual for further comments, as it works differently depending on if running V1 or V2 software. In V2, one Sigma can use Delta Control, the other will use traditional MIDI (ie two Sigma cannot access Delta Control simultaneously).

Note that they will all need unique IP addresses (just like phone numbers, all IP devices need a unique IP address).


Controlling Sigma Monitor Controls from an External MIDI Device on Windows

In some instances there may be need to control Sigma monitor controls from an external MIDI device that does not use the ipMIDI ports. For example, to map a MIDI keyboard 'Volume' control to the Sigma Level parameter.

On Mac OS this can be achieved using MIDI Patchbay software as stated in the Sigma User Guide.

On Windows 7 we have had success using an application called MIDI-OX to patch an external (hardware) MIDI port to an internal ipMIDI port which can be selected in the Sigma browser. For Windows 8 compatibility it is suggested to use the compatibility setting of XP SP3 during installation.

To set this up:

  1.  In Sigma browser designate an unused ipMIDI port as the MIDI LEARN port. In this example we will use ipMIDI Port 5.
  2. Download and install MIDI-OX:
    Note: Commercial use of MIDI-OX after the 30 day free trial period requires a license to be purchased.
  3. In MIDI-OX go to Options>MIDI Devices and select the external/hardware MIDI input port your MIDI device is connected to in the MIDI Inputs list and 05 Ethernet MIDI (ipMIDI port 5) in the MIDI Outputs list. Press OK to close this window.
  4. Test the connection you have just made by opening the  MIDI Port Activity Monitor under View > Port Status.... As you move a MIDI control on your hardware device you should see activity on the 05 Ethernet MIDI port.
  5. In the Sigma browser go through the MIDI Learn procedure as detailed in the User Guide to map the external MIDI control to a monitor control.

Repeat step 5 for mapping additional hardware MIDI controls to Sigma. 


Sigma Operation

Applying Processing to Sigma's Mix Busses

Sigma has insert points on both Mix A and Mix B stereo buses, allowing a multitude of processing options. Each insert point can be summed with a “dry” version of the Mix bus signal, as present on its insert send. This allows you to blend a combination of processed and unprocessed signals, making it easy to use parallel compressions effects.
The Insert section in the Sigma Browser’s Master page has contains buttons to switch the Insert In on each Mix Bus. The Accompanying ∑ buttons enable the clean signal and insert return to be blended together.
Note that insert send is always active, even when the return is not switched in to the Mix bus path.
The Mix A and Mix B busses can be summed together using the “B to A” function, which sums together the Mix B output with the Mix A output. The resulting signal is then sent to the Mix A output. This method can be used where level control is required over one or both of the Mix bus faders.


DAW Handshake

Leave DAW handshake button enabled (button lights green), if there are no other HUI/MCU devices on your network apart from Sigma.

Do not leave DAW handshake button enabled (button is grey) when there are other HUI/MCU devices present on the network. This would include, for example, SSL Nucleus.


Foot-switch Latching

The latching behaviour of any control assigned to the Sigma foot switch depends entirely on whether the connected pedal is latching or non-latching.


Level Drop when Switching a Sigma Channel from Stereo to Mono

This is normal behaviour and due to the 4.5dB pan law to which all analogue SSL mixers adhere. When a signal is in the centre of the stereo image it is 4.5dBb down compared to when it is panned hard left or right.


Meter Scaling

The input level meters on Sigma can be set to +18, +22 or +24 dBu in the browser or Sigma Remote software.


Monitoring Through Sigma Without a DAW Open

In some cases the Sigma levels will be reset to -100dB when the DAW is closed. This can mean that subsequent signals passing through Sigma are silent until the DAW is opened and the levels are reset.

If you wish to listen to audio without opening your DAW, for example from iTunes, press the 'Faders - 0dB' switch in the in the Sigma browser Channels page. This will reset all 16 Sigma channels to 0dB. 


Sigma Solo Modes

SIP (Solo-In-Place) Soloing a channel causes all other channels to be muted.

AFL (After Fader Level) Soloing a channel moves that signal onto a separate stereo mix bus, normally known as the AFL bus.

Sigma does not have a dedicated AFL bus. However, selecting the AFL option in SOLO MODE will hijack Mix Bus B and use this as an AFL bus. Sigma will automatically switch the monitor source selection to Mix Bus B when soloing in this mode.

AFL is useful when you want to solo a channel just to check something whilst printing a mix back into the DAW. If you were to use SIP, you would disrupt the printing process as soloing in this mode mutes all other channels.

Please note that when Sigma is put in in AFL Solo Mode, channels will not be able to be routed to Mix Bus B in the web browser. Also, upon changing to AFL Solo Mode, any channels currently routed to Mix Bus B will be un-routed.

By default, Sigma is set to SIP (Solo-In-Place).


Sigma and MIDI Controller Switch States

Some times Sigma functions may be assigned to a MIDI device back to front - i.e .on (lit) is off and off (unlit) is on.

If you have a MIDI device that has a lighting switch that you wish to assign to a Sigma control using the MIDI Learn feature, before assigning the control ensure that both the Sigma switch and the MIDI control to be associated with it are in the same state; ie both switches are off or both are on.


Sigma USB connection

The Sigma USB connection is for service use only.  Do not connect Sigma USB.

If the Sigma is started with the USB plugged in it is unlikely to start or work correctly.


Sigma Sweet Spot

As with all SSL consoles, Sigma has a sweet spot where the SSL sonic character is most pronounced. This is achieved by pushing the mix bus, or buses, slightly hotter than usual such that a small amount of harmonic distortion and compression is introduced into your mix. This sonic character is a subjective matter that may not be to everybody's taste so these are guidelines only for experimentation purposes.

To hit the sweet spot of Sigma it is recommended to:

  1. Keep DAW outputs as high as possible before clipping. This is recommended to keep signal to noise ratio at its optimum anyway. Using DAs which operate at +24 dBu as Sigma does will yield the best results here.
  2. Tip: Using a small amount of brick wall limiting on your DAW output buses on transient signals can allow you to achieve higher output levels.
  3. Keep the Sigma faders at 0 dB or above.
  4. Reduce the level of the mix bus, or buses, to avoid clipping your ADC on the way back into the DAW for printing your mix.

This way of operating sends a high signal level into the Sigma mix buses where there is a large amount of available headroom, and subsequently attenuates the mix bus to bring the mix back into a normal operating range.

This technique could, for example, be used on only mix bus B which is subsequently feeding mix bus A, so you can select which signals you would like to benefit from this effect by routing them to mix bus B. By keeping the master mix bus A in a more conservative operating range you can route signals that you wish to remain 'clean' directly to mix bus A.


Controlling Sigma from iOS

SSL launched a dedicated iOS Delta Control App in 2016, and there are several other options:

  1. TouchOSC can control all channels and the monitor section.
  2. Under the A-FADA protocol, TouchOSC can be used to control Sigma’s monitor section.

See the Sigma manual for further information.


Dropouts When Using Sigma 2.1/33

Please update to V2.1/53 (the latest version as of April 2021).

We have received reports of intermittent audio dropouts on V2.1/33 software.

The Remote software is still 2.1.33.


Connecting Sigma Directly to a Windows Computer

Please note, point-to-point Ethernet connections are not recommended for SSL network-based products. Network devices should be connected to networks (switches or routers), not directly.

Please see Dealing with multiple Ethernet adapters for more information.

If you must use a point-to-point fixed IP connection to Sigma, you must configure the Windows Local Area Connection/IPv4 to use Sigma’s IP address as the default gateway. In other words, the Sigma IP address will be used in the gateway field on the PC:

  1. Open Control Panel > Network and Internet > Network and Sharing Center > Change Adapter Settings.
  2. Right-click on the Local Area Connection and select Properties.
  3. Click on Internet Protocol Version 4 (TCP/IPv4) and then click on Properties.
  4. Select “Use the following IP address.”
  5. Enter an IP address for your computer, for example
  6. Make sure the subnet mask is
  7. Enter Sigma’s IP address (the default is in the default gateway field.
  8. Click ok.

Please see these articles for further information on SSL, networking, and ipMIDI:



Sigma does have a talkback input. The talkback circuit can be controlled by a foot switch.

Note that the Sigma talkback input is line level so a microphone preamplifier must be used to to amplify the microphone output up to line level. Sigma does not have a microphone preamplifier.


Power Supply and Consumption

Sigma comes with an external power supply. The power consumption of Sigma is less than 60 Watts.


Viewing DAW Audio Waveform and Sigma Automation Data Simultaneously

It can be useful to see the volume automation data of a Sigma channel on top of the audio waveform that it is controlling.

Example: Snare drum track being sent to Sigma Channel 2. To do this:

  1. Set the DAW track assigned to Sigma Channel 2 to 'no output'
  2. Copy the audio from the Snare track to the Sigma Channel 2 track

This means that automation data will appear 'on top' of the audio waveform, providing a clear indication of where the automation changes occur in relation to the audio.


Viewing Sigma IP Address

If there is trouble connecting your browser to Sigma, the process to view its current IP address is to briefly press both USER assignable buttons simultaneously.

The IP address that Sigma is using is now displayed on the front panel LEDs, as four separate 3 digit numbers in turn.

For example, if the numbers 192, 168, 001 and 105 are displayed in turn on the Sigma front panel, type ’’ into the browser URL field and press Return to connect to it.


Connecting 16 Outputs on Two DB25 Connectors to Sigma's Inputs

First, it should be noted that in order to enjoy maximum ease of use from Sigma with regards to handling mono and stereo signals, it is necessary to connect 32 outputs (on 4 x DB25 connectors) to Sigma's own 4 x DB25 connectors.
For instance, connecting the outputs of two Alpha-Link MX 4-16 (with 2 x DB25 output connectors per Alpha-Link), would allow each Sigma channel to be switched to mono or stereo at any time, according to the requirements of your current project, with no re-patching necessary.
Clearly in some cases, a full complement of 32 outputs may not be available from the DAW. For instance, if a single Alpha-Link MX 4-16 is used, it will provide only 16 channels across 2 connectors. If these two connectors are linked to two Sigma DB25 input connectors with DB25 to DB25 cables, Sigma will only be able to handle 8 signals (which may be mono or stereo).
In order to feed 16 mono signals into Sigma, it is necessary to use all of its four DB25 input connectors. So to follow up with the Alpha-Link MX 4-16example, one DB25 output on the Alpha-Link should be connected to two DB25 inputs on the Sigma.
This would require special cables to be made, and it would make it difficult to handle stereo signals when necessary.
So the best solution for this kind of configuration would be to use a patchbay: connect all the DAW outputs and Sigma inputs to the patchbay, then manage the connections with patch cables to handle stereo pairs or mono signals as required by the project you are working on.


Sigma OSC

Please find complete information on Sigma Open Sound Control functionality in the legacy user guide available on the Sigma documents site.

Sigma control for zero latency monitoring from the SSL Live console is detailed in the Live manual.


The Sigma DB25 Connector Pinouts

The D/B25 connectors use the TASCAM/AES59 pinout.
Please refer to the pinout tables at the very end of the Installation Guide for details.


Sigma Troubleshooting

Registration Issues

Sigma serial numbers start with SI, Not a 1 or an L. Please make sure the SI prefix is used when registering.  For example SI0987.

In addition, owners of Sigma with a serial number in the format SI2xxx may experience an Invalid ID number error when registering.  In such a case, please insert a 0 (zero) between the SI and 2xxx.  For example a serial of SI2000 becomes SI02000.


Loss of Communication Between Sigma, Remote App, Delta Control Plug-ins, or Control Surface

When using the Sigma Delta ensure that:

  1. The correct boot order is used.  That is: Sigma, control surface, and Remote app before the DAW and Delta Control plug-ins. If at any point Sigma, the control surface, or the Remote app is closed or rebooted while the DAW and Delta Control plug-in is open, the system must be booted from the start to ensure proper communication.
  2. The Remote app must be open on the computer at all times while the DAW is open in order for Sigma and the Delta Control plug-in to communicate. This includes situations where an iOS or OSC device is being used to control Sigma.
  3. Firewall may be blocking communication Sigma Communication. Turn off the OS firewall and any other firewalls that are active as a test.
  4. Turn Wi-Fi off.  If Wi-Fi is turned on it will redirect network traffic to the Wi-Fi instead of Sigma and cause connectivity issues. 

Sigma and Firewall

You must allow the Sigma Remote app through the your OS firewall.

To test if your firewall is blocking an app, temporarily turn your firewall off.

Control Panel\All Control Panel Items\Windows Defender Firewall\Allowed apps



Sigma Not Showing Signal on  Even Numbered DAW Outputs

If a Sigma channel is in MONO, only the signal present at the left input is used. This correlates to DAW outputs and subsequently audio interface outputs 1, 3, 5, 7, etc.

The right, even numbered (2, 4, 6, etc) DAW outputs, audio interface outputs and Sigma inputs are ignored in this case.


Sigma is Responding to Logic Channels Above 16

To lock Sigma to the first 16 Logic channels, first navigate to Logic > Preferences > Control Surfaces > Preferences.  Then un-tick the box 'Control Surfaces follow Track Selection'.

Sigma will then be locked to the first 16 Logic Channels and channels above 16 will not affect its levels.


Sigma is not Displaying the Exact Same Value as DAW Software Faders

Sigma interprets values according to the Mackie Control protocol, but the values received are entirely determined by the DAW and DAWs are not all exactly the same in terms of how they implement the protocol.
In any case, please bear in mind that Sigma is an analogue device, and therefore going over 0 dB in Sigma does not have the same meaning as in your DAW. Within a DAW, going over 0 dB means unpleasant clipping (although it's not noticeable if it only lasts a very short time like a few samples), whereas in Sigma going over 0 dB will first result in pleasing colouration of the sound.
So, the way to proceed with Sigma is to refer to the sonics, and not focus on the dB values numbers in the DAW. And do not hesitate to push the Sigma faders over 0 dB if it sounds good.