Guarda qui:
formatting link
da cui faccio copia & incolla. In pratica i due transistor prelevano la Phantom con gli emettitori e alimentano la capsula dai collettori; il segnale audio, viceversa, dalla capsula arriva bilanciato sulle basi ed esce dagli emettitori. L'ho provato, è perfetto.
Ciao Gianluca
-----------------------------------------------------------------------------------------
Better electret microphone phantom powering circuit This circuit provides lower impedance output than the circuit above:
+-----o---------------------330R--------+ | | | | 2k2 +---10k----+ | | | | | | | | | E--o---|--------------- COLD | o---------||----o--o-------B | | | 1u0 | C | | |+ +-100k-+ | | | CAPSULE |---o------o | |- +-100k-+ | | | | | C | |+ o---------||----o--o-------B | 10u | 1u0 | E--o---|--------------- HOT |- | | | | | | +---10k----+ | | | o----+ | 2k2 +| |+ | | 12V 10u | | -| |- --o-----o---------------------------------o----o---------- GROUND Component EBC is a PNP bipolar transistor (for example BC479 [o BC557, BC558 o altri a basso rumore]). Ideally these should be hand-picked for low noise and matched gain. Bear in mind that VCE can be up to about 36V. The 1u0 capacitors should be high quality plastic film types. The circuit may benefit from the addition of 22pF capacitors in parallel with the two 100k resistors. For minimum hum pickup the two 2k2 capsule bias resistors should be accurately matched.
Source: PZM Modifications web page by Christopher Hicks.