RME Word Clock Module

WCM

Word Clock Module for DIGI96 Series

Professional Word Clock Input and Output - plus Masterclock and Test Generator!

The WCM (Word Clock Module) adds a word clock input and output in professional quality to the DIGI96 Series. A low jitter optimized PLL circuit, an integrated clock generator and a unique test mode extend the powerful capabilities of our digital audio card in a way many professional users have asked for.

Like with our other products we were not satisfied with the commonly used standard circuits. Instead thanks to a newly developed input stage the WCM gains unsurpassed compatibility and reliability. LED's for power, test mode and LOCK clearly tell what's going on. With this the WCM stands in the same tradition as our other products: easy to use, always reliable, best performance!

Technical Specifications and Features

Module needs no drivers and no socket on the mainboard

Low jitter design: < 8 ns in PLL mode (44,1 kHz)

PLL works without dropouts even at more than 40 ns jitter at input

High sensitive input stage works from 1 Vpp input level

Ignores DC offsets in the word clock net

Overvoltage protection at input and output

Short circuit protected output stage

Integrated clock generator, useable as master clock or for test purposes

Frequency range PLL input: 27 kHz - 100 kHz

Frequency range output: 27 kHz - 100 kHz

Input BNC, high impedance (> 100 kOhm)

Output BNC, low impedance (10 Ohm)

Power supply: from DIGI96 board, 12 V DC, 40 mA

Standard slot, board dimensions 97 x 50 mm

4 internal cables, 1 BNC T-adapter and 1 BNC 75 Ohm terminator included

DIGI96/98 PAD® Settings Windows 95/98/NT

Thanks to the intelligent co-operation of Word Clock Module and the DIGI96 Series their combined usage is very easy. The activation is done by a simple mouse click on 'Word Clock' in the area 'Clock Mode' of the settings dialog. The area to the left, 'Output Status', allows to check whether the word clock is used by the card or not. When a valid input signal is present the third line changes from 'Clock Master' to 'Word Clock'. This display works exactly like the green LOCK LED at the BNC input. Therefore you'll see directly on your screen when a valid word clock signal is received and used by the WCM.

The display of the sample frequency in the second line of 'Output Status' does not represent the actual frequency in this mode, but the channel status set in the digital audio signal.

Unique Technologies in WCM®

Test generator/Master clock

Pushing the switch 'Test Mode' forces the WCM to generate its own quarz crystal controlled 44,1 kHz word clock, and to send it to all connected DIGI's. With this the internal generator provides two functions: Test mode (the internal word clock signal replaces the external at the BNC jack) and master clock. The master clock allows to synchronize all internally connected DIGI's. As the word clock signal of the test generator is available at the WCM's output too it can also be used as house clock, synchronizing the complete network (studio) with its 44,1 kHz signal.

Low Jitter Design

Usual devices using an internal word clock PLL generate up to 40 ns of jitter. The WCM's PLL is jitter optimized and typical lower than 8 ns at 44,1 kHz and 5 ns at 48 kHz. These values are achieved although the WCM's PLL is located on a separate board and stressed by electromagnetic fields inside the PC.

Wide Range

The WCM is propably one of the first devices in the world that supports the whole frequency range of 27 kHz to 100 kHz! With this you get the technology of tomorrow today.

Signal Adaption Circuit

An ideal word clock signal is a 5 Vpp square wave. Usual word clock input circuits are build with simple TTL receivers. Unfortunately often errors appear, caused by wrong impedances (more than one termination resistor), bad cables, connectivity problems or abnormal capacitive load, which lead to a loss of level and signal deformation. Because of this the WCM was equipped with a special AC coupled input circuit, that is able even to accept a sine as input signal, as long as its level reaches at least 1 Vpp. While other devices stop to work at 3 Vpp or at slightly deformated signals the WCM stays locked. Thus the reliability expected from a professional device can be guaranteed.

Protection Circuits

To guarantee a long and successful operation the WCM's inputs and outputs are protected against DC, overvoltage and shorts.