Hi, so I've been testing the PWM output with a capacitor on an oscilloscope.
The results are not really what I'd hoped for, it's around 0.83v ripple with a 470uF cap. I've not got many componants so I haven't got much to experiment with, I've got a 0.047uF cap but that never really charges to make much difference on the signal at all. I'm going to get some of those Silonex LDR's (if that's the brand people are using for the lightspeed attenuators) and see what they react like to the normal un-smoothed PWM signal.
Also, I've totally not been thinking. The forward bias voltage on the LED!!!!! There's only around 400 steps that the Arduino can output via PWM that can be used on the LED, and that's not taking into account what the LDR will pick up, I don't know how sesitive the amp is aswell.
Do you know what values of resistors make a discernable difference on volume?