Direct Monitoring on Focusrite Scarlett 2i2

Here's how to use "direct monitoring", which is available in many modern audio interfaces.

The gear I will be using is:

• Focusrite Scarlett 2i2 USB audio interface
• Lap-top Windows PC
• Creative 245 stereo speakers (with integrated TRS cable)
• Ableton Live 8 lite DAW
• Two TS 1/4 inch cables (90cm each)
• Zoom G2 guitar processor 
• ESP LTD M-100 electric guitar circa 2001

First of all, take a quick look at figure 1 to see the setup that i'm using.

Figure 1. The Setup

Here is a little explanation of the setup above:

The guitar is connected to the input of Zoom G2 via TS cable 1, the output of Zoom G2 is connected to the Scarlett interface via TS cable 2. The interface is connected to the PC via usb, Creative speakers are connected to the headphone output of the interface for monitoring.

I will use two different DAW configurations to demonstrate the use of direct monitoring, hardware configuration will remain the same as above except for the "Direct Monitor" switch on the interface. 

Lets start with "Direct Monitor" OFF on the interface hardware. Here is the channel configuration on Ableton Live 8 Lite:

Figure 2. DAW channel setting 1

The configuration on figure 2 was default when I first started the new project. Yours might be the same or a little different, but make sure that you click the Rec Channel button on the right hand side, and set software monitoring to auto and we're ready to play the guitar. - or NOT?

In the above configuration, you can feel that whatever you play comes out of the speakers with delay, which may cause you to run out of sync while trying to record. You can think of the signal flow like that:

Figure 3. Latency

Looking at figure 3, you can imagine that whatever signal you send to the interface, is sent to the PC via USB (Step 1) where it is processed and recorded and sent back to the interface (step 2) since we turned software monitoring ON. On step 3, sound comes out of the speakers with a delay, because of the processing time taken between steps 1 and 2. 

To overcome this problem, we need to turn Direct Monitor ON on the interface hardware, so that whatever you play is sent to the software to be processed and recorded, but what you hear actually bypasses the processing step and sent directly to the speakers. Take a look at figure 4. 

Figure 4. Direct Monitoring

Note that there is no step 2 in this configuration. In order to eliminate step 2, change your DAW channel Software monitoring setting to OFF. 

Important Note: Low software monitoring latency can be achieved with different driver settings or faster hardware, but for the sake of this lesson, all you need to know is that processing always takes some amount of time, and direct monitoring is an easy way to avoid sync problems while recording.