After extensive trial and errors, 20mH primary inductance was found to give a good male voice balance for the Sennheiser MD421 used at distances of less than 1/4in.
A Pleiaades transformer of 1:7 was connected to the grid of an EF183 through a capacitor. Plate, g3, and g2 were connected together. 4MOhms were connected from plate to grid ! And Plate supply voltage was 4.5V!
A load resistor of 15K was used to feed a transistor mic input stage through a coupling capacitor.
Sound was very clear, low noise (even when used in a noisy environment), every voice nuisance can be heard but somehow sibilants or naturalness leave something to be desired. Prior experiments with a Grampian ribbon mic terminated with a Pleiades 0.6mH and feeding an Altec 4722 feeding the EF183 stage gave very promising results of naturalness that you can only listen at BBC voice announcements. Hiss left something to be desired. No free lunch in nature.
A Pleiaades transformer of 1:7 was connected to the grid of an EF183 through a capacitor. Plate, g3, and g2 were connected together. 4MOhms were connected from plate to grid ! And Plate supply voltage was 4.5V!
A load resistor of 15K was used to feed a transistor mic input stage through a coupling capacitor.
Sound was very clear, low noise (even when used in a noisy environment), every voice nuisance can be heard but somehow sibilants or naturalness leave something to be desired. Prior experiments with a Grampian ribbon mic terminated with a Pleiades 0.6mH and feeding an Altec 4722 feeding the EF183 stage gave very promising results of naturalness that you can only listen at BBC voice announcements. Hiss left something to be desired. No free lunch in nature.
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