- The VIN pot's value doesn't actually matter that much. It's a potential divider. All the value will affect is how much the volume will roll off. I stuck in a 4.7K linear pot and it's feeble but enough.
- I can't stress this enough: check your grounds! I got a LOUD buzzing noise the first time I powered it up; transpired my input ground (hanging off the 10K pot in the schematic) had come loose. Oops.
- This thing is noisy. Like, tube amp noisy.
- That Pin 7 bypass cap is not optional. Well, it is, but it shouldn't be. If you omit it the 386 will motorboat (oscillate) like a washing machine with a bad brick habit.
- The pot I have seems to be dying a slow death, not only is it stiff, but there seems to be a short in there somewhere, because the op amp starts slamming into the rails with quite some force - acting as a voltage comparator instead of an amplifier - if you so much as knock the pot a little bit. I think I lost high frequency hearing in one ear and a heaphone driver finding this out...
- I added a series RC filter between 1 and 5 for bass boost; I didn't have a .033uF capacitor to hand - of course, TI had to choose the one value I didn't have - but I did have a .047uF polyester cap, which seemed to work just as well. Doing the math it will push the bass boost down from 190Hz to around 140Hz (frequency decreases as capacitance increases) but that's not a problem for me.
These are the values I used for the lowpass:
(I'll post a pic of the finished project as soon as I get the camera back...)
Oh and finally, the eagle eyed among you will notice the change in design - I was getting sick of grey and orange, so I've gone for something a bit more minimal. Hope you like!