This passage is from Ron Dethlefson's book "Edison Blue Amberol
Recordings, Volume 2, 1915-1929", ISBN 0-9606466-4-4, page 417:
"The following document [4-27-1929 memo - W.H. Sullivan to C.S Williams
Jr.] shows that Blue Amberols were electrically dubbed, probably in an
attempt to make them sound as good as other low priced electrical records
offered by dime stores and other record makers. [. . .] Just when
electrical dubbing began is unclear. I have noticed a marked improvement
in fidelity in my Blue Amberols beginning about record No. 5600 in late
1928, but electrical dubbing could haven begun as early as November 1927,
when the first electrical Diamond Discs were dubbed to cylinders."
I personally haven't heard any of these 5600 or 5700 series Blue
Amberols. Edison NHS has a good set of the electrical Edison discs, but
not any of the 5600-5700 series Blue Amberol dubs.
At a certain point, both Edison and Columbia companies redesigned their
wax cylinder dictation phonographs to use microphones rather than speaking
tubes for recording. David Morton's "History of Recording Technology"
website, referring to wax cylinder dictation phonographs,
states: "Electronics and microphones, both well-advanced by the 1920s,
were not used at all in dictation until the late 1930s, and even then
the "acoustic" models were still in use for many years." [See:
I have heard electrically recorded dictation cylinder experiments. One
test that survives at Edison NHS is actually a microphone comparison.
It would take some searching, but it probably would not be too difficult
to determine a more precise date for the Edison Co's switch from speaking
tube to microphone wax cylinder dictation machines. If this would be
helpful, please send an email request directly to my NPS email address.
Edison National Historic Site, West Orange, NJ