RME HDSPe MADI FX [18/87] Clock modes synchronisation

User's Guide HDSPe MADI FX © RME

11.3 Clock Modes - Synchronisation

In the digital world, all devices must be either Master (clock source) or Slave (clock receiver).

Whenever several devices are linked within a system, there must always be a single master

clock.

A digital system can only have one master! If the card’s clock mode is set to 'Master', all

other devices must be set to ‘Slave’.

The HDSPe MADI FX utilizes a very user-friendly, intelligent clock control, called AutoSync. In

AutoSync mode, the system constantly scans the digital input for a valid signal. If any valid sig-

nal is found, the card switches from the internal quartz (Clock Mode – Current Internal) to a

clock extracted from the input signal (Clock Mode – Current MADI, Word, AES or Sync In). The

difference to a usual slave mode is that whenever the clock reference fails, the system will

automatically use its internal clock and operate in clock mode Master.

AutoSync guarantees that normal record and record-while-play will always work correctly. In

certain cases however, AutoSync may cause feedback in the digital carrier, so synchronization

breaks down. To remedy this, switch the HDSP clock mode to ‘Internal’.

RME’s exclusive SyncCheck technology enables an easy to use check and display of the cur-

rent clock status. Input Status indicates whether there is a valid signal (Lock, No Lock) for each

input (Word, MADI, AES, Sync In), or if there is a valid and synchronous signal (Sync). See

chapter 30.2.

Via Clock Source a preferred input can be defined. As long as the card sees a valid signal

there, this input will be designated as the sync source, otherwise the other inputs will be

scanned in turn. If none of the inputs are receiving a valid signal, the card automatically

switches clock mode to ‘Master’.

Under WDM the card will (has to) set

the sample rate. Therefore the error

shown to the right can occur. A stable

signal with a sample rate of 32 kHz is

detected at the Word Clock input

(Sync), but Windows audio had been

set to 44100 Hz before. The red

colour of the text label signals the

error condition, and prompts the user

to set 32000 Hz manually as sample

rate.

Under ASIO the audio software sets the sample rate, so that such an error will usually not hap-

pen – but it can too. In slave mode the external sample rate has priority. Feeding 44.1 kHz will

prevent the ASIO software to set 48 kHz – obviously, as the only way to do so would be to enter

a different clock mode (Master/Internal).

In practice, SyncCheck provides the user with an easy way of checking whether all digital de-

vices connected to the system are properly configured. With SyncCheck, finally anyone can

master this common source of error, previously one of the most complex issues in the digital

studio world.