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Tutorial
F/B (FEED-BACK) MODE
Although the Bus Compressor side-chain per se has a 'feed-back' topology, the signal feeding
the side-chain is derived from a feed-forward position. Engaging the F/B switch derives the
signal feeding the side-chain from a feed-back position (i.e. after the main gain-reduction
VCA in the audio path). This results in a more 'relaxed' style of compression, in contrast to the
traditional 'grab' of the Bus Compressor.
Usefully, because the MAKE-UP Gain on The Bus+ is implemented using an MDAC gain
stage (post feed to side-chain), instead of via the VCA (pre feed to side-chain)
4K MODE
When 4K MODE is disabled, the main VCA operates in a balanced configuration, optimised
for low noise and distortion. This is the approach of all modern SSL SuperAnalogue Bus
Compressor designs found in Duality & AWS consoles.
Engaging 4K MODE does two things. Firstly, it changes the operation of the VCA from balanced
to unbalanced (matching how the Bus Compressor in a 4000-series console was implemented)
and secondly, it introduces a variable amount of harmonic distortion via the VCA. These two
factors combine to allow for a more 'coloured' sound. Adjusting the distortion amount, you'll
find there's a certain 'sweet spot' (depending on your mix level) in which your material will
become more cohesive, thanks to the added thickness.
Since distortion is not achieved by means of overloading (amplification),
there is no inherent noise penalty from using 4K MODE even at the highest
distortion settings).
4K MODE - ADJUSTING THE DISTORTION SETTING
There are 9 levels of distortion to choose from. The current distortion setting is
indicated by the colour of the switch when 4K MODE is engaged. The Bus+
ships from the factory set to level 5 of 9.
To alter the distortion setting, press and hold the 4K MODE '[SET DIST]' switch
until it starts flashing. Then, use the - and + switches to decrease/increase
distortion. Press and hold the 4K MODE switch to finalise and return the - and +
buttons to their standard functions (LOW THD and F/B).
MIN
DISTORTION
1
2
12
DEFAULT
3
4
Press and hold 4K MODE until it starts to flash
Use the - and + keys to decrease or
increase the amount of distortion
5
6
DISTORTION
7
8
THE BUS+ User Guide
MAX
9
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