[quote author="PRR"][quote author="jdbakker"]from a noise POV any resistance between IN- and 'ground' will appear in series with the impedance on IN+. The 2k resistor will also boost the effect of current noise[/quote]
2K
in parallel with the microphone. The mike will short-out the base current noise and the 2K's thermal noise. Or more accurately: it couples one input's noises into the other input as a Common Mode noise, which will be rejected.[/quote]
For the 'regular' circuits linked upthread with just one THAT1510 that's true, but I was talking about the two-1510 design that was linked to the first post of this thread (
http://www.tenmilecreek.net/DC_Preamp/DC_Preamp.pdf). In that circuit, the noise voltage of the 2k resistor between the negative input of each THAT1510
will be added in series with the microphone's signal.
Or am I missing something ?
[quote author="mediatechnology"][quote author="PRR"]I'm also thinking that fairly simple discrete circuits ought to eat 0V-48V input without the flying-rail contraption, but might be just as much trouble.[/quote]
Show me one.[/quote]
If you don't care much about power consumption or DC-offset on the outputs, how about a Cohen/Green front-end topology with hi-voltage discrete op-amps (like the SGA-SOA) subbed for the '5532/072 ? Have a look at everything up to and including IC1ab on
http://mhumhirecords.org/DIYpics/Green/gren_pre_cct4.gif , for example; there's no real reason that can't be made to work on a higher supply with the use of a good DOA.
JDB
[working on similar, but still trying to find a way to get rid of the output coupling caps]