Any mods for XLT?

[derick]

I tried increase +5V TX section to higher voltage.Maximum for stability was around 6v,but I had no deeper effect.(Air test)Also I tried change value R1 825ohm resistor in RX section to 680ohm.XLT was little deeper,but I heard every stone as "hot rocks".Next step I change OPAMP MC33078 to LME49720,maybe better stability,but no noticeable better depth.After this mod audio discrimination tone is going higher.