SLAA936A September 2020 – March 2021 TAS2563
One very important task is to neutralize every step of the signal chain before tuning, so as to start with the natural speaker response. As a best practice, determine at all times which steps of the signal chain are enabled and which affect the sound. For instance, the user should bypass all equalization (EQ), dynamic range compression (DRC) , smart amp protection, and input gain as much as possible at the beginning of any tuning. Bypass any preprocessing of the audio originating from the system host as well. When using the in-system tuning tool to tune a product through USB, any audio processing from the host processor must be bypassed.
A recurring check that can prevent frustration throughout the process is to ensure that the system gain is set to a known reference value. The soundcard playback volume found in a Windows audio device configuration (often available as a shortcut key on the keyboard) is responsible for setting the system volume in the case of EVM tuning. In the case of a reference device used for comparison, such as a mobile phone, the volume buttons on the phone hardware usually control the phone system volume. Ensure that the system audio setting does not have an artificial limit that prevents the device from achieving the maximum volume.
The personal computer (PC) and mobile device scales can often differ in step size, so when comparing two sound sources it is best to simply keep all device system volume at the maximum. Setting the source volumes at the maximum specification allows for the maximum SPL out of the smart amp and ensures a fair comparison to a reference source. This practice also accounts for the artifacts of high-volume tuning, such as unwanted distortion and compression.