The following image is the first of an analysis done on the 25W amplifier. The date, 4.July 1980 indicates that this was done after I left EC (which was in 79, at least on a full time basis. After a short break 80 or something, I returned on a consultancy basis to do some more for them until some time in 1982.)
I will upload the whole analysis. For those technically inclined it should be interesting. Lots of similar analysis were also done earlier. I got the feeling that many people believed we were only some kind of non-serious hippies or something. Well, in a way we were outside the establishment, but we did our mathematics ! Also note the point made at the end of the note, saying that feedback below 20 db is no good idea, when it comes to distortion.