RME OctaMic II handleiding
Handleiding
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User’s Guide OctaMic II © RME
21
12.2 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. Actually you will find all the necessary
components (T-adapters, terminators, cables) in most electronics and computer stores. The latter
usually carries 50 Ohm components. The 75 Ohm components used for word clock are part of
video technology (RG59).
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. If the voltage is too low, synchronization will fail. High frequency reflection effects can cause
both jitter and sync failure.
Unfortunately there are still devices on the market which provide 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. In some cases 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 (such a device is generally recommended for bigger studios).
Therefore it seems of advantage to design outputs of word clock as low impedance types, but all
word clock inputs as high impedance types, in order to not weaken the signal on the chain.
The OctaMic II's word clock input can be high-impedance or terminated internally, ensuring max-
imum flexibility. If termination is necessary (e.g. because the OctaMic II is the last device in the
chain), push the switch at the back (see chapter 9.1).
In case the OctaMic II resides within a chain of devices receiving word clock, plug a T-adapter
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 T-adaptor and terminator plug.
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Productinformatie
| Merk | RME |
| Model | OctaMic II |
| Categorie | Niet gecategoriseerd |
| Taal | Nederlands |
| Grootte | 3434 MB |
