OceanAudio The Arc 900 Owner's Manual - More On Levels When Using
Ark - Owner’s Manual - Revision 3 - page 29
More on levels when using
Digital
Audio
Interfaces
The Ark has been designed to operate at standard professional operating levels
‘0’ on the VU meters corresponds to +4dBm (1.225V),
‘0’ on the master bargraph meters corresponds to 0dBm (0.775V).
When connecting a Digital Audio Interface it is important to set the levels of your interface, so it matches correctly
with the console. Digital interface levels are generally calibrated in dBFS (dB Full Scale) and they do not directly
correlate to dBm.
For example, 0dBFS can be equivalent to +24dBm. Since 0dBFS is the maximum level which can be handled by the
Digital Audio Interface, you should not set 0dBFS to be the same as 0dBm.
Setting your interface output to 0dBFS is obviously going to cause severe headroom problems through the console.
Similarly, setting the interface input to 0dBFS means that you are going to require a large output from the console to
drive the interface.
A more sensible approach is to set the interface input and output levels to between
-20dBFS (+4dBm equivalent) and -24dBFS (0dBm equivalent).
Check the manual of your interface for instructions on how to do this.
The way to check that you have the levels set to their optimum for working with the ARK is to adopt the following
procedure:
Set the interface output to between -20dBFS and -24dBFS and connect it to the console channel line input. Make
sure the channel input level control is set to it’s midway (centre detent position) and that the channel fader is set to
maximum. With the channel VU meter set to read the channel direct output, play a signal through the channel. Use
a test oscillator or a synth set to generate a constant sine-wave tone of about 1kHz (two octaves above middle C).
The VU meter should read around ‘0’ on average and maybe peak into the red area on occasional peaks. If the
signal level is not high enough or is too high, adjust the interface output so that the signal gives a similar reading on
the VU meter.
When connecting to the input of an interface, send a signal from the console that again reads around ‘0’ on the VU
meter with occasional peaks into the red and adjust the interface input level so that it reads between -24dBFS and
-20dBFS. This can be reduced (anywhere between -18dBFS and -12dBFS) in conjunction with the manufacturers
instructions for the best operating level.
Make sure to repeat this for every input and output of your interface.
Once the interface is set up to match the console using the above method, connecting to any of the other console
inputs such as channel monitor inputs or sub group returns will ensure that the levels are matched correctly.
Sound on Sound magazine did a very good background article on this subject, which can be freely consulted at the
following link :
http://www.soundonsound.com/sos/may00/articles/digital.htm
While this article dates from May 2000, the information is still valid.
Important Note :
If your Digital Audio Interface features digital D-Sub connectors, DO NOT connect them to the Ark’s D-Sub
connectors. Only connect analogue D-Sub connectors from your Digital Audio Interface to the analogue
connectors of The Ark.