I realised as I was going to bed that if I wanted to drive 600 Ohm loads with the NE5532's I couldn't put a 50 kOhm pot in front of it.
So, today I'm experimenting with reversing the last op-amp and the pot. My biggest concern is that the power supply noise that was previously driven down by the 5:1 attenuation in the pot will come back up. If the noise looks low enough, I'll just make this one final change and have the board made. Otherwise I'm going to have to consdider adding more power supply filtering, and perhaps some RF filters on the input to the buffer and final stage.
Stay tuned!
Erik
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