VU meter noises entering the master output
Here's a clue: -

If you read the data sheet for the 1968 vintage dinosaur op-amp aka the 741 you would see this: -

If you converted to the μA741 you can run on supplies as low as +/- 5 volts: -

But, the 741 is a crock of sh1t poo really and you should be using something a little more modern.
Reasons not to use a 741 op-amp?.
However, if you want to resolve this methodically, remove D1 here: -

And see if the problem you get is still present. If the problem is still there at least you know it's something to do with the 741 circuit.