I'm working on a record that has me puzzled. It's a Gennett record from
1923. The authorities say that Gennett didn't take up electrical
recording until 1926 or so, so I had this pegged as acoustic.
But it has *hum* on it. Significant hum; at this stage in processing the
signal (two channels combined, no EQ, iZotope de-clicking applied) the
hum signal is at about -38dBFS (about 24dB below my nominal 0vu level).
There's also an intermittent signal at 40Hz. The lowest signal frequency
seems to be about 150Hz
If this is an acoustical recording, how did those low frequencies get
onto the record? If there was a mechanical rumble in the room, I would
not expect the recording horn to respond significantly at 57Hz, let
alone 40Hz. (Heck, 150Hz is surprising.)
And the thing is, it doesn't *sound* like an acoustical recording --
there aren't the typical horn resonances coloring the sound. It sounds
like a good early electrical recording.
But the 1923 date is reinforced by several sources -- well before
Gennett is believed to have gone electric.
Could this have been an experimental electrical recording (perhaps using
the GE Photophone process) that somehow escaped into the catalog? Could
it be turntable rumble during cutting? If so, why does the record sound
electrical rather than acoustical?
By the way, the flip side has virtually identical hum, though a cursory
glance doesn't show the 40Hz component.
Anyhow, I'm mystified. I know that record companies were experimenting
with electrical disk recording before the majors adopted the Western
Electric system, hence my speculation that this could have been one of
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