I noticed use of the TL074 and MC33078. I’m sure much has changed in IC op-amp design since the VC7 was designed (as well as pricing and availability). I imagine there’s some value in upgrading these. Perhaps with less nose and/or more gain?
Is that feasible? Maybe wishfull thinking.
Or else , just any recommendations based on what you may have learned lately while working on the new voice channel? (Sorry, I do like to tinker