These are (in my opinion) failures (out of spec) on the production line. I tested 10 of these before I found one that worked satisfactorily. The main problem seems to be that the gain is way out of spec; somewhere too high, somewhere too low. A few pieces wouldn't even miss the right signal. All were tested at minimum gain (Av=20). I followed the datasheet with the recommended schemes for testing. Most of them had "popcorn noise", although I was able to tame it by adding a 10kΞ© or less resistor on the signal side of the input coupling capacitor. Some had sustained vibrations of 5.5MHz. The recommended output suppression (0.05uF in series with the 10 ohm resistor) wouldn't suppress it (and in some cases cause motor boating), but 0.015uF directly at the output did the trick. You MUST tightly bridge the power wire with at least 10uF. Also, when used in a circuit where the load is sometimes removed (e.g. a speaker jack) it would be advisable to connect a load of around 22-47 ohms to the output. Some of the issues mentioned may be exacerbated by the fact that I need to drive a 16 ohm load (32 ohm headphones with elements connected in parallel). The scoring is because as mentioned some of the chips were dead on arrival but if I get 5 good chips from the stack the price is still fair. Just be prepared to go through and find the ones that work properly.
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