Nemesis Audio
8
active receiver, so it should be hoped that a manufacturer has taken some care into implementing
some muting algorithms if the data is corrupt.
The period of corruption can also be minimized by ensuring the switch happens as fast as possible by
using high speed switching cores which will ensure that any clicks or pops will be isolated to as few
channels as possible, and by controlling when and where the switch happens, can also result in some
predictability about any unwanted noise. This can be achieved by matching the switching point to
the device word clock signal which gives the switching core a signal frame position reference.
By decoding the data into a workable stream of digital audio, a more robust method of switching
from one source to another can be developed, akin to switching an analogue signal and this is the
basis of Option 2.
This does however require a much larger amount of circuitry, higher processing power, and a core
that is able to understand the digital data being fed to it.
This could result in the loss of any proprietary control data being sent along with the audio data. It
also requires the unit to regenerate a MADI stream, and the switcher would then have to
understand any current formats but also any future formats that may arise, as well as the ability to
re-encode the afore mentioned proprietary data and function at any and all sample rates expected
by the receiving and transmitting equipment. It would also have to be able to generate its own
stable word clock and on-board highly accurate bit clock to avoid any data degradation from clock
jitter or misaligned bits.
Nemesis MADISW
A refined switching and routing solution based on Option 1 of the discussion above. The unit is
tailored to provide flexible switching between 2 MADI sources into a receiving input, whist also
taking care of redundant system connection, word clock distribution and format conversion between
optical and co-axial MADI connections.
Inputs and Outputs are provided on both 75 Ohm BNC connectors and SC-Fibre Optical Connectors.
The BNC links are rated for maximum travel of up to 60-100m, dependant on cable loss. The SC fibre
connections will allow links of up to 2km with appropriate fibre cables. Channel inputs are auto
sensing with optical taking priority and will fall back to the BNC connections when the Optical signal
is not present. This ensures input selection is not necessary and also provides a redundant input link
if cabling reliability is a potential issue.
The switched output appears at both the BNC and Optical outputs, and redundant links are again
available for connection to multiple destinations, such as mixing consoles with multiple engines (e.g.
DiGiCo SD7), or for use a distributor/split. 2 further AUX connectors allow programmable routing of
either additional output feeds, or input splits e.g. for connecting multitrack recorders.
A 2-channel world clock distribution amplifier ensures that a single word clock feed from a console
can drive the 2 MADI sources. The word clock signal is also used as a frame reference in the
switching core.
2 internal power supplies are wired together in a redundant configuration to improve reliability.
The switching core has been developed to switch as fast and cleanly as possible, and this helps to
minimise the period of corruption as discussed earlier. The word clock signal is also fed to the
switching core and the unit will schedule the switch from A to B on the rising or falling edge of the