Connecting to the SLink port
Posted by Keith Johnson, Last modified by Keith Johnson on 24 September 2019 08:24 AM

Protocols and modes

The intelligent SLink port automatically switches mode to enable connection to expanders or consoles with one of the following 3 protocols:


Network Speed

Sample Rate

Maximum Inputs

Maximum Outputs

dSnake (+ME)

Fast Ethernet (10/100)



20 (+40 ME)


Fast Ethernet (10/100)





Gigabit (1000)




Connection speed

The SLink port detects the speed of the connection, and then ‘discovers’ any expanders. This means that when trying to use switches or media convertors (for fibre runs), the speed of the device connected to the SLink port must be matched to the protocol being used.

Automatic Firmware Update

Once an expander is connected, the firmware is automatically checked and matched to the console.
The expander firmware required is different for each range of consoles, and can also change with updates to console firmware, so it is stored in the console and sent to an expander when needed.

When connecting the same expander to the same console (without changes to console firmware) connection will be very quick as the firmware will already be correct.

If a firmware update is required, it could take up to 2 minutes to complete. If the expander is connected at the end of a system (i.e. through another unit, or a DX hub) checking and updating may take slightly longer.

If your expander is having difficulty in connecting correctly at the end of a cascade, try connecting just that one expander directly first in order to ensure it is running the correct firmware.


When the initial connection is made, the ‘Lnk’ LED’s on the SLink port and expander will flash yellow rapidly.

If connecting to another system (another SLink port or a gigaACE option card) the ‘Lnk’ LED will then continue to flash yellow steadily on both ports at the same speed.

If connecting to an expander with mismatched firmware (or on first connection), the ‘Lnk/Err’ LED’s on the expander will flash red whilst the firmware is being updated. Once the update is complete the expander will automatically reboot.

When an expander is running the correct firmware, the ‘Lnk’ LED’s will then continue to flash yellow steadily, with the expander flashing twice as fast as the SLink port. The ‘Ready’ LED on the expander will also illuminate to show connection to the console.


The expander will be muted until connected to a console. When the ‘Ready’ LED illuminates, the expander will be unmuted.


Synchronising to a clock does not change the sample rate of the device, it just aligns the samples correctly.

Expanders are automatically clocked to the console they are connected to.

When connecting systems, one console should be the ‘master’ and any/all other consoles should be clocked to this. In the case of a direct SLink to SLink connection, either console can be the master. In the case of direct connection to a Qu, the Qu cannot clock to an external source so it must always be the clock master.

If a system is not clocked correctly, you will experience audible artefacts such as ‘clicks’ and ‘pops’ due to the misalignment of samples.

Sample Rate Conversion (SRC)

Each SLink port has built-in sample rate conversion, so when using 48kHz expanders or connections, incoming audio is up-sampled to 96kHz before being sent to the mixing core and down-sampled before being sent back out.

As SRC is independent per port, having multiple SLink ports on one system (through the addition of an SLink option card) enable different protocols to be used on each.
For example, one SLink port could be connected to a gigaACE option card in a dLive system (gigaACE) and the other could be connected to an AB168 (dSnake).

Preamp control

The only control information sent and received through the SLink port is for the control of preamps.

48V Phantom Power, PAD and Gain settings are adjusted from either the preamp processing section on an input channel, or by using socket controls from the I/O screen. Control messages are sent out to the expander, and the GUI is then updated to show the current state.

Possible configurations

The possible system setups for one SLink port are covered in the SLink connections document, available under the ‘Documents’ tab on the SQ product webpages here.

Any combination of two setups can be achieved on one system through the addition of an SLink option card.


  • Adding connections via SLink provides access to more inputs and outputs, but does not increase the number of processing channels available on the mixer
  • Multiple protocols cannot be used at the same time on a single port
  • An SLink port is for digital audio only, it does not send or receive system information and only preamp control data is sent/received
  • An expander can only be connected digitally to one console at a time, but sharing sockets across multiple consoles or systems is possible through the use of tie-lines
  • dSnake and DX protocols support a maximum of two remote audio units per port
    • The AR2412 and AB168 have dedicated expander ports for cascading units
    • It is not possible to connect two AR2412's to one port (as the maximum number of dSnake inputs is 40)
    • DX expanders should be set to Cascade mode with the second unit connected to port B
    • The second DX unit in cascade mode uses inputs and outputs 17-32. For example, with two DX168s connected directly, outputs 9-16 are unavailable and the outputs for the second unit are 17-24
    • The DX32 does not support cascade as it is a 32x32 unit.
  • The ME personal monitoring system can either be connected directly to the SLink port, to an Expander or Monitor port on AR2412/AB168, or to the DX2/ME port on GX4816 (with no DX expanders connected)
  • System to system connections use the gigaACE protocol when connecting SLink to SLink or SLink to a gigaACE option card
  • System to system connections make use of the dSnake+ME protocol when connecting to a Qu
  • It is not possible to connect SLink to the built-in gigaACE ports on a dLive MixRack. These ports are different to the gigaACE ports on an option card as they carry many more channels along with all the control information for a dLive surface
  • It is not possible to connect two consoles using the DX protocol as this protocol is for use with expanders only
  • The maximum distance between each connection is 100m. This means the distance from the SLink port to the first unit can be 100m, and the distance from that unit to a second can also be 100m
  • Cat5e (or higher) STP cable should be used throughout any system