UAD Powered Plug-Ins differ from native plug-ins in that they are processed exclusively by the DSP inside of our UAD-2 DSP Accelerator and Apollo devices, rather than being processed by the host CPU as native plug-ins are. Using this method of external processing leaves the host CPU free to handle the processing of DAW functions and other native tasks, but it does affect the way you need to configure your DAW when using UAD plug-ins.
When adding a UAD plug-in to a track in your DAW, the digital audio data must travel out of the host computer and to the UAD-2 device where it is processed. The processing of the digital audio is handled exclusively by the UAD-2 device, however the host CPU is still involved as it transfers the digital audio data to and from the UAD-2 device.
The I/O buffer size - which is found in Console Settings on Windows, and in the DAW settings on Mac - determines how much time (in samples) the host CPU has to move the digital audio to and from the UAD-2 device. Setting the buffer size lower gives the host CPU less time to move the digital audio and increases the strain on the host CPU which can result in pops, clicks, distortion, or other audio artifacts in the playback from the DAW. In addition to audio artifacts, a good indicator that the buffer size is set too low is high CPU usage in the CPU usage meter of the DAW.
If you are experiencing pops, clicks, distortion, or other audio artifacts when using UAD plug-ins in your DAW, first try experimenting with your I/O buffer size. Start at a higher buffer size, such as 512 or 1024, and incrementally lower the buffer size to find the optimal setting for your system.
How low you will be able to set the buffer size on any given system depends on the processing power & specs of the host computer, the amount of CPU being used by background processes & applications, as well as the type of UAD-2 device used.
Note: The recommended buffer size for all UAD-2 FireWire devices is 512 or higher.