The Melodium model 93C is a small diaphragm condenser measurement microphone that was on the market in the 1970s. Although the data sheet is not dated, the frequency plot is marked 03-73, which pins down the measurement, if not the manufacturer, to March 1973. The specimen on the bench was actually stamped with model number 530C, but seems to be the same microphone.
|Melodium 530C measurement microphone|
The 93C / 530C needs a 13V to 18V supply to operate, and a battery pack was available.
|Melodium 530C with battery pack|
The mic is not compatible with phantom power, but a simple converter can be built. In this case it was built into the old battery pack, with an indicator LED replacing the on-off switch.
|Melodium 530C with modified supply to convert from phantom power|
|Frequency plot for Melodium 550C, referenced to Beyer measurement mic|
When I wired this one up according to the manufacturer's data sheet, I found that the mic was out of phase with our reference mic, and indeed the data sheet claims that the 'Angle of phase rotation 180C to tension'.
Here is the manufacturer's data sheet for the Melodium 93C.
Thanks to Santiago Calvo Ramos for sharing.