dmp
Well-known member
I have a 902 de-esser that has distortion when turned up for gain reduction.
I'm trying to understand the circuit a little bit more. A few schematics attached.
My version is the most common that matches these schematics as far as I can tell, with RMS daughter boards and a dbx202x with 8 parallel THATs.
As I understand it so far, the Audio is split into a low pass (LP) and high pass (HP) components (the HP is created by subtracting the LP from the full bandwidth). The user set frequency control adjusts where the HPF is set. The HP and the full bandwidth (FBW) are sent to separate RMS detectors that each produce an average voltage corresponding to the signal levels, which go to a comparator. The difference of the HP to the FBW with the threshold (set by the range control) becomes the GR control voltage (CV), which goes to the VCA. The more high frequency energy relative to the FBW, the more compression.
There have been some discussions on here years back on operation of the 902, but all the images, etc... have been lost.
I'd be interested to understand what the trimmers are doing before I check the calibration.
I'm trying to understand the circuit a little bit more. A few schematics attached.
My version is the most common that matches these schematics as far as I can tell, with RMS daughter boards and a dbx202x with 8 parallel THATs.
As I understand it so far, the Audio is split into a low pass (LP) and high pass (HP) components (the HP is created by subtracting the LP from the full bandwidth). The user set frequency control adjusts where the HPF is set. The HP and the full bandwidth (FBW) are sent to separate RMS detectors that each produce an average voltage corresponding to the signal levels, which go to a comparator. The difference of the HP to the FBW with the threshold (set by the range control) becomes the GR control voltage (CV), which goes to the VCA. The more high frequency energy relative to the FBW, the more compression.
There have been some discussions on here years back on operation of the 902, but all the images, etc... have been lost.
I'd be interested to understand what the trimmers are doing before I check the calibration.
