Zenith Cobramatic Stroboscope - Muffled Audio?

[Electronic M]

Haven't seen a photo to know if this was one of the capacitive REAL cobra pickups, but if it is a normal audio signal from a normal audio source won't work.

The early cobras used a variable capacitance cartridge that NOBODY else made (and only wurlitzer bought from Zenith to use). The capacitance carts needed a tube RF osc that was modulated by the cartridge to make sound out of the variable capacitance. Zenith used this from 1948 until the late 50s when instead of making a stereo version they just used the stylized cobra tone arm with a conventional ceramic or magnetic cart.