User`s guide

User's Guide Babyface © RME

26. Technical Background

26.1 Lock and SyncCheck

Digital signals consist of a carrier and the data. If a digital signal is applied to an input, the re-

ceiver has to synchronize to the carrier clock in order to read the data correctly. To achieve this,

the receiver uses a PLL (Phase Locked Loop). As soon as the receiver meets the exact fre-

quency of the incoming signal, it is locked. This Lock state remains even with small changes of

the frequency, because the PLL tracks the receiver's frequency.

If an ADAT or SPDIF signal is applied to the Babyface, the corresponding input LED starts

flashing. The unit indicates LOCK, i. e. a valid input signal (in case the signal is also in sync, the

LED is constantly lit, see below).

Unfortunately, LOCK does not necessarily mean that the received signal is correct with respect

to the clock which processes the read out of the embedded data. Example [1]: The Babyface is

set to 44.1 kHz internally (clock mode Master), and a mixing desk with ADAT output is con-

nected to input ADAT. The corresponding LED will show LOCK immediately, but usually the

mixing desk's sample rate is generated internally (also Master), and thus slightly higher or lower

than the Babyface's internal sample rate. Result: When reading out the data, there will fre-

quently be read errors that cause clicks and drop outs.

In order to display those problems optically at the device, the Babyface includes SyncCheck

It checks all clocks used for synchronicity. If they are not synchronous to each other (i.e. abso-

lutely identical) the SYNC LED flashes. In case they are completely synchronous the LED is

constantly lit. In the above example the user would have noticed quickly that the LED kept on

flashing after connecting the mixing desk.

The same information is presented in the Babyface's Settings dialog. In the status display Input

State the state of the input clock is decoded and shown as simple text (No Lock, Lock, Sync).

In practice, SyncCheck allows for a quick overview of the correct configuration of all digital de-

vices. So one of the most difficult and error-prone topics of the digital studio world finally be-

comes easy to handle.