I want to design low noise balanced dynamic microphone pre-amplifier, but cheap enough with easily to find component in my country.
I use 2SB737 transistor which have very low rBB, but I'm not sure how much collector current to get lowest noise for 150 Ohm output impedance dynamic microphone.
In this simulation, the collector current is 2.7mA and voltage input noise is 1.7179312nV/Hz½ at 1Khz max. gain.
Simulation used ZTX951 because it have slightly lower rBB than 2SB737. I do not have 2SB737 model.
I use NE5532 op-amp because it is cheap. Dual op-amp is easily to find than single op-amp. In input stage NE5532 parallel, so I can used 560 Ohm feedback resistor.
Gain can be adjust from around 7 dB to 60 dB. Is it enough?
And one op-amp use for clip indicator than use for nothing.
Any suggestion are welcome.
I use 2SB737 transistor which have very low rBB, but I'm not sure how much collector current to get lowest noise for 150 Ohm output impedance dynamic microphone.
In this simulation, the collector current is 2.7mA and voltage input noise is 1.7179312nV/Hz½ at 1Khz max. gain.
Simulation used ZTX951 because it have slightly lower rBB than 2SB737. I do not have 2SB737 model.
I use NE5532 op-amp because it is cheap. Dual op-amp is easily to find than single op-amp. In input stage NE5532 parallel, so I can used 560 Ohm feedback resistor.
Gain can be adjust from around 7 dB to 60 dB. Is it enough?
And one op-amp use for clip indicator than use for nothing.
Any suggestion are welcome.
Good job.
When you go to actually build it you'll find the ZTX951 to be an excellent and consistent low noise performer.
When you go to actually build it you'll find the ZTX951 to be an excellent and consistent low noise performer.