User manual RME HDSPMADI

[. . . ] Preliminary User's Guide (see page 77) Hammerfall® DSP System MADI TotalMix 24 Bit / 192 kHz ü SyncAlign ® TM ZLM ® SyncCheck TM ® SteadyClock PCI Busmaster Digital I/O Card 64 Channels MADI Interface 24 Bit / 192 kHz Digital Audio Stereo Analog Monitoring 64 x 64 Matrix Router 2 x MIDI I/O MIDI embedded in MADI Quick Boot General Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Hardware ­ Connectors 6. 1 External Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. 2 Internal Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7 Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] This is especially true when extracting the word clock out of a MADI signal. Caused by the MADI format itself, such a signal will have around 80 (!) ns of jitter, which is reduced to about 1 (!) ns by SteadyClock. 23. 3 Cabling and Termination Word clock signals are usually distributed in the form of a network, split with BNC T-adapters and terminated with resistors. We recommend using off-the-shelf BNC cables to connect all devices, as this type of cable is used for most computer networks. You will find all the necessary components (T-adapters, terminators, cables) in most electronics and/or computer stores. Ideally, the word clock signal is a 5 Volt square wave with the frequency of the sample rate, of which the harmonics go up to far above 500 kHz. To avoid voltage loss and reflections, both the cable itself and the terminating resistor at the end of the chain should have an impedance of 75 Ohm. High frequency reflection effects can cause both jitter and sync failure. Unfortunately there are still many devices on the market, even newer digital mixing consoles, which are supplied with a word clock output that can only be called unsatisfactory. If the output breaks down to 3 Volts when terminating with 75 Ohms, you have to take into account that a device, of which the input only works from 2. 8 Volts and above, does not function correctly already after 3 meter cable length. So it is not astonishing that because of the higher voltage, word clock networks are in some cases more stable and reliable if cables are not terminated at all. Ideally all outputs of word clock delivering devices are designed with very low impedance, but all word clock inputs with high impedance, in order to not weaken the signal on the chain. But there are also negative examples, when the 75 Ohms are built into the device and cannot be switched off. In this case the network load is often 2 x 75 Ohms, and the user is forced to buy a special word clock distributor. The HDSP MADI's word clock input can be high-impedance or terminated internally, ensuring maximum flexibility. because the card is the last device in the chain), activate the switch TERM between the BNC jacks on the Expansion Board so that the yellow TERM LED lights up. In case the HDSP MADI resides within a chain of devices receiving word clock, plug a Tadapter into its BNC input jack, and the cable supplying the word clock signal to one end of the adapter. Connect the free end to the next device in the chain via a further BNC cable. The last device in the chain should be terminated using another T-adapter and a 75 Ohm resistor (available as short BNC plug). Of course devices with internal termination do not need Tadaptor and terminator plug. Due to the outstanding SteadyClock technology of the HDSP MADI, we recommend not to pass the input signal via T-adapter, but to use the card's word clock output instead. Thanks to SteadyClock, the input signal will both be freed from jitter and - in case of loss or drop out ­ be reset to a valid frequency. User's Guide HDSP MADI © RME 41 23. 4 Operation The HDSP MADI's word clock input is active when Pref. Sync Ref in the Settings dialog has been set to Word Clock, the clock mode AutoSync has been activated, and a valid word clock signal is present. [. . . ] Double Speed Doubles the original sample rate range, in order to achieve higher audio quality and improved audio processing. 64 kHz is practically never used, 88. 2 kHz is quite rare in spite of certain advantages. Quad Speed Controversially discussed way of ensuring hi-end audio quality and processing by quadrupling the sample frequency. 128 kHz is non-existant, 176. 4 kHz is rare, if at all then 192 kHz is used, e. g. [. . . ]