Total posts : 45366
The Vmid signal is a bit confusing. Are you limited to a single voltage power supply? If you are not then it would be better to connect U1 pin 3 to the power supply common and use a + and – supply.
The gain for U1 is likely too high.
There is a better op amp circuit for rectifying low level signals. Search on op amp precision rectifier. This will work down to millivolts so you won’t need much gain at all.
On the 4066’s you need to keep the audio signals between VDD and VSS limits, preferably midway between them. If you used a dual supply (+ and-) then the audio signal can be kept centered around ground and referenced to ground. Some CMOS switches are subject to latch-up if this isn’t done. This would be another advantage to using a dual supply.
It is not obvious but trying to use a single supply for an op amp circuit can cause all sorts of problems, for example the input impedance may not be constant.