User`s guide

User's Guide ADI-192 DD © RME

TDIF

After a HiFS addition to the TDIF-1 specification, and the introduction of Tascam's DA98HR, the

TDIF format officially supports up to 192 kHz. Even before that, the Double Wire and Quad Wire

methods could be used for the same purpose. In fact Double Wire is identical to the sample

multiplexing of HiFS. Apart from the DA98HR, practically no device with TDIF interface supports

more than 48 kHz. Therefore the ADI-192 DD does not use the - partially incompatible - HiFS

method, but instead uses the more common and 100% compatible methods Double Wire and

Quad Wire to realize higher sample rates.

A TDIF input signal of 48 kHz could effectively be 48 kHz (no RANGE LED), 96 kHz in Double

Wire (LED RANGE DS) or 192 kHz in Quad Wire format (RANGE LED QS). Therefore, the

range has to be configured manually.

8.3 Clock Decoupling using the SRC

Master-slave problems occur at the latest with the use of a digital mixer. For 'normal' use of CD-

player, DAT and hard disk recording, the tasks are clearly defined. The device playing back is

the master in each case, the recording device the slave. The CD-player delivers the clock and

the DAT synchronizes to it.

When working with a digital mixer, the CD-player would be the master and the mixer the slave.

This model breaks down with a single stroke, if a DAT is also being connected, which is not

recording, but also playing back. Every digital device can only synchronize to one source, the

audio data of the other sources is processed with errors due to missing synchronization. Clicks

and drop outs are the consequence.

Normally, the mixing console works as master and delivers a reference signal (word clock) to all

other devices. But this is only possible, if the other devices have a sync input, i. e. are capable

of being slaved. In a studio with digital tape machine, digital effects and hard disk recording,

common CD-players and DATs cannot be connected to the mix section of the console, simply

because they cannot be synchronized.

This is no problem, if a sample rate converter is being used. It synchronizes any input signal to

the desired sampling rate, re. the desired clock reference.

By this, any device can be connected via the ADI-192 DD to any other device in a studio with a

central clock, independent from its original capabilities. Instead of the CD-player or the DAT, the

ADI-192 DD is the slave now.

8.4 The SRC as Signal Conditioner

DAT tapes often show little formatting errors between the various recorded takes. There can

also be tiny snippets with other sample rates between the recordings. An SRC converts this

patch-work reliably into a continuous permanently valid data stream with a fixed sample rate.

Even if there are unformatted spots on the tape, or the DAT is being stopped or switched off,

the ADI-192 DD delivers a constant signal (which does of course not contain audio information

in this case).

The use as supplier of an uninterrupted data stream is also helpful for applications that would

otherwise suffer from functional errors or automatic switch-off of devices. Thanks to the SRC,

the ADI-192 DD always delivers a constant output clock, no matter if the inputs are not being

used at the moment, are just being connected or have been used all the time.