On older compressors, quite often there was no threshold. It is actually a fixed value (not the entire range), but it's hard to know what that value is (-1, -5, -10, etc...)
So how do you control it? Adjust the input gain! Increasing the Input Level is similar to lowering the threshold. The two always work hand in hand when they are both available.
Example (using both an input and threshold)
Input signal is at -10db
Threshold is set to -5 db
In that situation, no compression will ever occur, because the signal level does not meet the threshold level. To get around that, you either:
A: raise the input to -5 or higher
B: Lower the threshold to -10 or lower
Since this particular compressor has no threshold to lower, you can only use the input level to raise the signal enough that it hits the pre-set threshold. It's not ideal, and does not provide as much control or transparency, but that is how it fundamentally works - the same as it did on the SSL channel strips the pro channel is emulating
Hope that makes sense. And if I have provided any errors (it's a very basic explanation) I'm sure someone will correct me.
post edited by codamedia - 2011/05/05 15:12:20