Lynx Studio Technology:LStream Loopback

LStream™ Loopback

What is loopback?

Loopback is simply routing an output channel back to an input channel so you can record what is being played. This can be used for recording a soft-synth performance, capturing audio that is being played from a web browser, creating a sub-mix of multiple input channels to record to a single stereo pair, or any situation where it is not practical or possible to capture what is being output from the audio card any other way. Both the input and output loopback channels must run at the same sample rate.

Loopback on the LynxTWO-A and L22

The LynxTWO-A and L22 have dedicated loopback channels. Outputs 5 & 6 on the LynxTWO-A, and Outputs 3, 4, 5 & 6 on the L22 are dedicated loopback channels. These loopback channels appear on the LynxTWO-A record device input selection as "Loopback In R" and "Loopback In R", and on the L22 as "Loopback In 1" through "Loopback In 4". You may still wish to use the internal LStream™ expansion port on the LynxTWO-A or L22 to give more channels of loopback.

Internal LStream expansion port loopback

The internal LStream expansion port on the LynxTWO, L22 and AES16 is intended to connect LStream expansion modules such as the LS-ADAT or LS-AES to the main audio card for Digital I/O expansion. The LStream port accommodates up to 16 channels (depending on sample rate) of external I/O. If you do not have an LStream expansion module connected to your main audio card, you may use the LStream port for up to 16 channels of loopback.

Physical Connection

To use the internal LStream expansion port for loopback, you must connect a 0.100" jumper between pins 2 & 4 on the internal LStream expansion port on your Lynx audio card.

Enlarged view of 0.100" jumper

It is not necessary to use a jumper that looks exactly like the example in the photograph. Any 0.100" jumper will do. Many hard disk drives have 0.100" jumpers on them for master/slave selection. You might be able to harvest a jumper from a discarded hard disk drive.

Example of jumper placed between pins 2 & 4 on an AES16.

How to install the Jumper

1. Turn off the power to your computer and unplug the power cord.

2. Open the computer chassis. Refer to your computer documentation for precautions and instructions on how to do this. Be sure to touch metal inside the computer case to ground yourself and discharge any static charge you may be carrying.

3. Locate your Lynx audio card and place the 0.100" jumper between pins 2 & 4 of the internal LStream expansion port. Use the example photograph above as a guide. Please note the photograph is of an AES16 so the components below the three connectors may look slightly different on your card, but the LStream connector and two clock connectors are the same on all LynxTWO, L22 and AES16 cards. This photograph has the card with the D connectors to the right, component side up.

4. Replace the cover to the computer and plug the power cord back in.

Software Settings

The LStream expansion port will carry all 16 output channels that are displayed in the LynxTWO Mixer's output window:

Example of LynxTWO-A Output window from LynxTWO Mixer.

It is important to note that Outputs 9 though 16 are labeled "LStream Out 1" through "LStream Out 8". These channels will show up in the Record/Play page as "LStream 2 In 1" through "LStream 2 In 8". Outputs 1 through 8 will show up on the Record/Play page as "LStream 2 In 9" through "LStream 2 In 16".

Example of LynxTWO-A Record Channel Selection Menu.

On the LynxTWO and L22, the default routing will have Record 5 through Record 8 listening to "LStream 2 In 1" through "LStream 2 In 8". This is the ideal situation as no extra routing will be required on your part. All you would need to do is select "Play 5" as the playback device in your application, and that audio will routed to the inputs of the "Record 5" device.