SPL Iron V2 Two-Channel Tube Mastering Compressor (Black/Silver) - Manual (Page 16)

16
Control Elements
Tube Bias
The Tube Bias switch allows you to determine the bias of the tubes according to three set-
tings: Low, Mid, and High. The bias of a tube is the voltage present on the tube‘s grid. The
higher the voltage, the less signal makes it from the cathode to the anode of the tube,
which means the compression is stronger.
Cathode
Grid
Bias voltage
Audio signal
Audio signal
Anode
The modulation of the bias is the sum of the Threshold, Rectifier, Side Chain EQ, Attack
and Release parameters.
Attack
Attack determines the response time of the compressor. Put simply, it is the time that the
compressor needs to respond once a signal is above the threshold. It indicates how long
it takes the compressor to perform 63% of its work. The Attack time can be adjusted in
six steps, from Fast to Slow.
The IRON does not offer the possibility to set an exact Attack time, since it is not a con-
stant value and it depends on the rest of the parameters.
Medium Attack times
To get an inconspicuous compression, set a middle-of-the-road Attack time and then
reduce it carefully until you can hear some distortion. Right at that moment you should go
back a bit and you will have reached an ideal compromise.
Longer Attack times
If you want to use the compressor to shape sound and to highlight the attack phase of an
instrument, you should use longer attack times.
Long Attack times and short Release times
The use of extremely long Attack times and shorter Release times is called Leveling,
because the compressor then hardly reacts to to any level changes and always keeps the
signal at the same level. That way, short dynamic changes in the music are not affected,
only long-term volume variations are processed.