Sony ECM-250 electret condenser microphone with Pleiades (R,L) filter

Very interesting microphone.


The schematic shows just a capsule, a FET and a 1.5V battery through an output transformer. Almost exactly like a Pleiades V6 or K117 booster amplifier.


It sounds very nice.


But there is some hiss showing that moving coil mics can be quieter. In fact connecting a Shure SM63 directly to Sony TC-D5 Pro produced more output and less noise without a booster amp.


Signal path:


Make singing voice at 1-4in - Sony ECM-250 - Pleiades filter - Sony TC-D5 Pro - Sennheiser HD580


The ECM-250 can sound even more natural than the SM63. But there is breath noise, poo noise. Sibilants are fine and HF detail very nice.


To improve signal to noise ratio a Pleiades filter of 330mH was connected at the output of the mic. Mic can now be used at 1-2in as proximity effect is compensated and signal output is greatly increased.


The gentle slope Pleiades (130Ω,40mH) sounds very nice too with this microphone.