Overview

ASIO-Guard is Steinberg’s performance optimization technology introduced in Cubase 7 to address one of the most common challenges in digital audio production: CPU overload and audio dropouts. 
Many users often run dozens or even hundreds of tracks with complex plug-in chains, which can cause real-time processing bottlenecks. ASIO-Guard mitigates this by pre-processing audio tasks that do not require real-time calculation.

Background

In a typical DAW, all audio processing happens in real time, meaning every track and plug-in must be calculated within the audio buffer window (e.g., 5.33 ms (256 samples @ 48 kHz)). If the CPU cannot complete these calculations in time, you experience dropouts, clicks, or pops.
ASIO-Guard introduces a second processing buffer for tracks that are not record-enabled or monitored. This buffer is much larger than the real-time buffer, giving the CPU more time to process these tasks in advance. The result: smoother playback, higher track counts, and fewer interruptions.

How ASIO-Guard Works Internally

Cubase’s and Nuendo’s hybrid audio engine splits tasks into two paths:
 

Real-Time Path

• Handles tracks that depend on live input: 
  • Record-enabled tracks
  • Monitored tracks
  • External instruments and effects
• Uses the audio interface buffer size (e.g., 64–256 samples)
• Is processed with high scheduling priority 
• Must complete calculations within each buffer cycle to avoid dropouts.
   

ASIO-Guard Path

• Processes tracks that are not receiving live input
• Uses a larger buffer (often several times bigger than the real-time buffer).
• Pre-calculates audio data ahead of time and stores it in a prefetch queue.
• When playback reaches that point, Cubase/Nuendo simply streams the pre-rendered audio, reducing CPU load during critical moments.
   

Dynamic Switching

If you enable monitoring on a track, Cubase/Nuendo instantly moves it from the ASIO-Guard path to the real-time path - the same applies to VSTi tracks when record-enabled (!). This dynamic switching ensures input monitoring with low latency. Note that low latency comes with a price: using "heavy" plugins in the live path can earlier lead to dropouts.
 

Benefits

• Improved Stability: Fewer audio dropouts during playback and mixing.
• Higher Track Counts: Efficient CPU load distribution.
• Lower Latency for Recording: The real-time path remains responsive while background tasks are pre-rendered.
   

ASIO-Guard Levels

[Cubase/Nuendo 15 or older]
You can select Low, Normal, or High in Studio > Studio Setup > Audio System > Advanced Options.

[Cubase 16]
You can select levels 1-5 in Edit > Settings > Audio > Advanced

• Off
• Level 1 (23 ms pre-processing time - former Low)
• Level 2 (35 ms pre-processing time - former Mid, standard)
• Level 3 (93 ms pre-processing time - former High)
• Level 4 (140 ms pre-processing time)
• Level 5 (280 ms pre-processing time)
   

Restrictions

ASIO-Guard does not apply to:

• Record-enabled VSTi/MIDI tracks
• Any monitored tracks
• External effects and instruments.
• Certain plug-ins (check in VST Plug-in Manager).

Practical Tips

• Use ASIO-Guard level 2 as a starting point, unless you experience dropouts.
• For automation recording, etc., consider Level 1/Low or disable ASIO-Guard for immediate feedback.
• Audio Performance Monitor supports you with finding overloads and bottlenecks and offers to adjust settings accordingly.
• Use higher levels for
  • projects and templates that could barely play (or not at all) in earlier Cubase releases (Cubase 15 or older)
  • projects and templates with many audio tracks and instruments in playback or with resource-intensive plug-ins in the signal path
• Projects might not significantly benefit from higher ASIO Guard levels if the signal path contains a lot of heavy VST instruments and master effects, long effect chains, and numerous dependencies between tracks using side chains or groups.