Q: I'm getting clicks, pops, distortion, and/or other audio artifacts when using the digital input on my Apollo Twin. What do I do?
A: Clicks, pops, distortion, and/or other audio artifacts when sending digital audio from one device to another are typically caused by the two devices not being synchronized to the same clock. Each audio device capable of sending digital audio output via ADAT or S/PDIF has its own internal clock. To avoid digital audio artifacts, you need to choose which device will be the master clock source, and which device will be externally synced (slaved) to the master clock.
Apollo Twin does not have a way to send its clocking signal out to an external device - it has no outputs that can carry clocking signal such as ADAT, S/PDIF, or Word Clock - so when sending digital audio from an external device into the Apollo Twin you must sync the Apollo Twin to that external device's clock via the incoming digital signal.
Apollo Twin’s clock source is set with the CLOCK menu at the bottom of the Console application window (or the CLOCK SOURCE menu in Console Settings > Hardware). If the external device is sending ADAT signal into the Twin, set the Twin’s clock source to ADAT. If the external device is sending S/PDIF signal into the Twin, set the Twin’s clock source to S/PDIF. You also need to make sure the Twin’s DIGITAL INPUT menu (in Console Settings > Hardware) is set to match the digital audio type (ADAT or S/PDIF).
If the Twin is unable to sync to the external clock, the selected clock source is displayed in red. When the Twin has detected the external clock the clock source is displayed in white. Make sure that the external device's clock source is set to “Internal” (or the equivalent setting) when syncing Apollo Twin to external clock.
If you are sending S/PDIF signal into the Apollo Twin from an external device, you have the option to use the SR CONVERT feature in Console. SR CONVERT converts the sample rate of the incoming digital audio in real time to match the sample rate of the Apollo, eliminating any clicks, pops, distortion, or other audio artifacts that would otherwise be present if the two devices were not set to the same sample rate.
To enable this feature, click on the SR CONVERT box above the Inserts section on the S/PDIF Console channels - the feature is enabled when the box reads "ON" as shown below.
S/PDIF Console channel with SR CONVERT enabled