TL084 being used as an unity gain Amplifier. The second opAmp in half wave recitification configuration. The third opamp is in unity inverting configuration. The second and third opAmp input is obtained from output of the first. The fourth op-amp input comes from the third invertor config opamp output and the fourth is also in half wave rectification mode. The opAmp is powered with linear +12V -12V supply I am completely redesigning my circuit and want to have the following changes.

1. Replace the +12V and -12V linear supplies with some cheaper and less board space alternative. There is another thread addressing this issue.
2. Replace the two half wave rectifier stuff