dCS 904 User Manual

Manual for Software Version 1.5x and 1.36

dCS Ltd

June 2000

 

 

The overload indication given by the dCS 904 is comprehensive. The detection circuitry monitoring the digital filter does not simply check the final output word but all the data from which the output word is formed. If any of these overload (this may not be apparent from the output data), an overload is flagged.

The filter itself has sufficient numerical accuracy that if the input data is not overloaded, the filter computations cannot generate an overload - only a raw data overload can cause an error. The overload indication is thus much more accurate than any external meter based indication - for this reason it is stored in the AES/EBU validity bit for later reference.

ADC/Data

Menu

Set

The ADC/Data button is dual function – on its own (blue type on the front panel) it sets the input mode (analogue or digital). With the other menu buttons ( white type on the front panel) it is the menu Set button.

As an input mode switch, it switches between the analogue inputs (ADC mode) or a digital input on the AES Reference input (Data mode).

Data mode routes the digital input through to the outputs, and makes noise shaping, word length reduction and some reformatting available to it. For normal operation, this is set to ADC (LED off). In Data mode, the ADC/Data LED lights and the data stream on the AES Reference Input is output on the AES1-4 outputs. If the Reference Input sample rate is 88.2 or 96kS/s and the Output Format is Dual AES, the input will be converted to Dual AES on AES1 & 2 and AES3 & 4.

Data mode also affects the SDIF connectors (BNCs) in any DSD mode. The data lines (two of the four connectors) become inputs, and DSD fed into these is packed and re-formatted into the output format selected. No DSP is carried out.

For Menu operation as the Set button, see the section “The Software – the Menu” on page 18.

Master/Slave

Menu

Down

The Master/Slave button is dual function – on its own (blue type on the front panel) it sets the clocking mode (master or slave). With the other menu buttons ( white type on the front panel) it is the menu Down button.

In Master mode, the calibrated voltage controlled crystal oscillators (VCXOs) inside the unit generate an accurate sample rate. The LED labelled Master will be lit to indicate this. If a Master Clock is available, this may be connected to the Reference In connector (for AES/EBU reference) or the 75R In connector (for SDIF-2 Word Clock). To slave the unit to the Master Clock, press the Master/Slave button. The unit will attempt to lock to the Reference - this will take a few seconds. If lock is achieved, the Slave LED will light up brightly and the Master LED will turn off. To return to Master mode, press the Master/Slave button again.

If both AES Reference and Word Clock are connected, pressing the Master/Slave button cycles through the sequence:

Master ... AES Reference ... Word Clock ... Master ... etc.

Manual part no: DOC135904 iss 2B2

Page 14

135904ma2b2.pdf file available from website

Contact dCS on + 44 1799 531 999

email to: more@dcsltd.co.uk

(inside the UK replace + 44 with 0)

web site: www.dcsltd.co.uk