Apollo Software Manual v7.0 - zZounds.com

Latency BasicsLatency (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-latencymonitoring), it always exists to some degree when working with systems that combineanalog and digital audio. These concepts are explained in greater detail below.Audio Interface LatencyEvery audio interface that performs A/D and/or D/A conversion induces latency as a resultof 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 lesslatency (higher rates = less time required for conversion).An audio interface’s “analog I/O round-trip latency” specification refers to how long ittakes for an analog signal at an interface input to reappear at the same interface’s analogoutput after both A/D and D/A conversion. Apollo’s audio interface analog I/O round-triplatency is 1.1 milliseconds at a sample rate of 96 kHz.Console Mixer LatencyApollo’s Console Mixer is used for low-latency monitoring (cue mixing) of Apollo’s analogand digital inputs. Using Console to monitor Apollo’s inputs may or may not add to theinherent analog I/O round-trip latency, depending on how it is configured:Console without UAD plug-ins – When Console is used without UAD plug-ins, monitoringApollo’s inputs via Console does not add any latency. In this configuration, Apollo’sanalog I/O round-trip latency is still 1.1 milliseconds at 96 kHz.Console with Realtime UAD Processing – When Console is used for Realtime UAD Processingwith UAD Powered Plug-Ins that are not upsampled, monitoring Apollo’s inputsvia Console does not add any latency.In this configuration, Apollo’s analog I/O round-trip latency is still 1.1 milliseconds at 96kHz, even if up to four UAD (non-upsampled) plug-ins are serially “stacked” (chained) ona single Apollo analog and/or digital input.Multiple Apollo inputs can have up to four UAD (non-upsampled) plug-ins each (up tothe limit of available DSP resources); this configuration also does not add any latency.Note: Upsampled UAD plug-ins add latency when used in Console or a DAW. See“Upsampled UAD Plug-Ins” below for details.Console Auxiliary Buses – The outputs of the auxiliary buses in Console have 32 samplesof additional latency. This is necessary to maintain the lowest possible input latency.Apollo Software Manual94Chapter 7: Latency & Apollo