Corsair Opamp Hiss Reduction

Between the product detector output and the AF amplifier input on the Corsair's IF/AF board, there are between 7 and 11 RC4136 opamps in the audio signal path, depending on whether you have the BP Filter engaged. The RC4136 is a relatively noisy opamp by today's standards and has non-standard pin-outs. Cimarron Technology makes an adapter specifically intended to replace RC4136 with modern opamps, specifically the OPA2134 in SMD packaging. Note that when you're soldering the SMD chips to the BrownDog carrier boards that pin #1 for the SMD soldering is denoted with a silk-screened circle and pin #1 for RC1436 plug-in compatibility is the square pad.


I removed the RC4136 DIP-14 chips from the IF/AF board and installed DIP-14 sockets. I then plugged the BrownDog carrier boards into the sockets. Here's a photo of the IF/AF board with the new opamps installed:


Below is the audio spectrum taken with minimum RF Gain for the Corsair with RC4136 opamps (aqua) and OPA2134 opamps (yellow). Please ignore the spikes. Generally speaking, there is about a 15dB reduction in noise (hiss) with the new opamps.