I bought yet another one; and it cost me £10.95! This one again is marked BM-800. I took it to pieces (of course) and spent a happy hour tracing the circuit. It’s clever and not at all ‘cut price’. It contains a respectable FET head amplifier and some circuitry to work correctly from a conventional 48V phantom system via a regulator and impedance converting transistors. So I have done some more scientific testing and compared it to one of my own old JM47 mics….. The ‘ten quid’ mic is very good, and in terms of ‘quality’ it has the ‘big condenser’ sound but the noise level is a couple of dB higher than my old faithful. It does have that indefinable character that electret mics possess; it’s a slightly ‘cooler’ sound than the old fashioned expensive mics that cost about 50 times as much.
So once again I would recommend the cheepo mic, particularly as the current models work perfectly well direct with a phantom powered mic pre.