Opto Compressor :-

This opto compressor is based on the silver faced Urei LA-4 compressor that uses a 4136 op-amp in it's detector circuit. You can find more information in the data section of this site.

If you want to see information on the black faced Urei LA-4 you can find a schematic at Waltzing Bear's web site: see links.

The basic idea was to take the detector and attenuator part of the Urie LA-4 circuit and put it into the unbalanced section of the balancing box. The balancing box is a well proven and tested design that relies on the qualities of the SSM2142 and SSM2143 special purpose ICs and the trusty LM833s for op-amp duties. We could have used a more modern chip like a TLO74 in the detector but chose to use the original 4136 as in the Urie LA-4 since it was still available.

The new twist on an old idea provides all the flavour of the old design but with less noise and distortion due to the qualities of the SSM chips.

To look at the circuit of the Urie LA-4 , that this compressor is based on see the data section. LA-4 schematic.