TF3MA, Fös Mar 29 10:18:32 GMT 2002
The TF3MA dynamic mic preamplifier
Þessi síða hefur verið heimsótt 
sinnum síðan 7. Júní 2003
Based on the N0MF preamp I made a preamp for my K2 to be able to
use it with an old Sansui dynamic mic.
The frequency response of the preamp is flat from 60Hz to 6kHz,
when C1 is 0.22uf.
The gain is +14dB into a 1k load (the mic input on K2). The preamp
draws approx 0.8mA current from the 5V source.
The gain can be increased to +20dB by changing the 10k resistor to 5.6k.
This doubles the current drain.
The low frequency cutoff is controlled by C1, for my old microphone I use
0.022uF (LF cutoff 800Hz) to get a better balanced voice response,
the Sansui mic has to much bass.
By adding a series RC network across C1 the frequency
response of the mic/preamp can be altered to fit the mic.
Assume that the input resistance to the base of the transistor is
25k when designing the RC network.
73 de TF3MA