In the Artscroll biography, Rav Dessler, R Yonason Rosenblums writes:
Rabbi Dessler even sought to tape his shiurim in Ponevezh Yeshiva and send the tapes back to England. The idea of a tape recorder in the beis medresh, however, was still novel in those days, and he was advised not to do so. (Page 312)
I, however, am curious, if anyone out there has ever heard or even owns recordings of Rav Dessler? I was once told that recordings were made at one point. I’ve seen hand written letters and shiurim he has sent talmidim, but it would be amazing to actually hear a recording of Rav Dessler.