User's Manual

Apollo Solo USB Manual Latency & Apollo Solo USB 222
Latency Basics
Latency (delay) is an inherent factor in digital audio systems because of A/D-D/A
conversion, I/O buffering in the DAW, plug-in signal processing, and other aspects.
Although there are ways to mitigate latency (such as delay compensation and/or
low-latency monitoring), it always exists to some degree when working with systems that
combine analog and digital audio. These concepts are explained in greater detail below.
Audio Interface Latency
Every audio interface that performs A/D and/or D/A conversion induces latency as a result
of the conversion process. This inherent A/D–D/A latency is essentially undetectable.
A/D–D/A latency usually depends on the sample rate, with higher sample rates inducing
less latency (higher rates = less time required for conversion).
An audio interface’s “analog I/O round-trip latency” specification refers to how long it
takes for an analog signal at an interface input to reappear at the same interface’s analog
output after both A/D and D/A conversion. Apollo Solo USB’s audio interface analog I/O
round-trip latency is 1.1 milliseconds at a sample rate of 96 kHz.
DAW Latency
Most DAWs use hardware I/O buffering to shuttle audio data back and forth between
the audio interface and the DAW. This I/O buffering induces additional latency with any
audio interface (not just Apollo Solo USB).
I/O Buffer Size
The amount of DAW latency is usually determined by the DAW’s I/O interface buffer size
setting. With Apollo Solo USB, the buffer is set in the Hardware panel within Console
Settings. Low buffer sizes reduce latency, but increase the host computer’s CPU loading.
If the buffer size is set too low, host CPU overloads and/or audio artifacts such as clicks,
distortion, or dropouts can occur.
Monitoring Live Performance During Recording
DAW latency can be a problem during recording when software monitoring via the
DAW’s mixer, because the buffering delay is a distraction; an artist cannot hear their
performance in realtime. DAW latency when recording with Apollo Solo USB is mitigated
by using Console for live performance input monitoring, where I/O buffering latency does
not apply.
Time-Alignment Of Newly-Recorded Tracks With Previously-Recorded Tracks
Dealing with latency is also important with DAWs for time-alignment of newly-recorded
tracks and previously-recorded tracks which are inevitably shifted from the I/O buffering
process.
The solution is to use the automatic delay compensation (ADC) feature of the DAW.
Modern DAWs, and Console, have automatic delay compensation. For more information
about system latency and its compensation, see Delay Compensation with Apollo Solo
USB USB.