On the recording end, what were the cutting lathes and associated amplifiers say from 1925 to 1935? What improvents were made over that decade? What were their distortion characteristics and specifications?
Also, on the other end, playback during that time ?
That's an enormous question; I suggest you look for "Frequency Response of Grooved Media" by Peter Copeland of the UK's "National Sound Archive". It can be found on the internet. It is very detailed.
