Omni C - IC1 Replacement Audio Mod

(addapted from posts to Ten-Tec reflector June 2005 by AB0N)

Consider changing the IC Op Amp in the AGC circuit. This is not a 100% cure for the AGC popping but I found it to help on all but the strongest signals. I used a Burr Brown OPA2604AP Dual Op amp in there. I did the experiment several years ago. As memory serves the TI TL072 or 82 chips were good but I liked the Burr Brown chip mentioned above. Burr Brown was aquired by TI. These parts are still available from DigiKey. I think the reason this chip change works so well has to do with it's low distortion and faster slew rate. I tried some faster Analog devices chips but found little was gained with them. My suggestion is to install a high quality socket (8 pin). And try a few parts under listening conditions as I did. Power rig down for swaps. You will still need to adjust the RF gain for the stronger signals but the popping to my ears is less annoying. As always your mileage may vary. I hope this helps.

(although suggested in the context of improving AGC popping, this chip replacement should provide a noticeable improvement in the overall audio quality)

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