The biggest disadvantage of the principle is, that the very slow reaction of the LDR makes it impossible to implement fast attack times. On the other hand this disadvantage is connected to the soft and low distortion signal treatment of this 'Soft Compressor'.
The threshold control has a range from -30 dB to + 20dB. The control for attack and release times have control ranges from 3 to 50 ms for attack and 0.1 to 5 s for release. The ratio setting determines the control characteristic of the device within the range from 1:1 (Off) to oo (which means limit). As the optical regulation device is by far not as linear as a VCA, the operation range of the soft compressor is limited to about 20 dB of gain reduction. Within that range the ratio control works somewhat okay but there is still not a really linear characteristic. Of course, this 'error' contributes its part to the desired sound. As there is no real chance to implement a rather proper working autogain circuit, an additional 'make up' gain control determines the output level of the device.
The display for the gain reduction has 8 LED's and a range of 20 dB.
The I91 soft compressor fits into a 4U high INTEGRATOR mounting frame.
Balanced and floating inputs and output