I need a preamp with 50 Million OHMS

[eatyourguitar]

I sold someone a contact mic shaker and he doesn't have a HI-Z preamp with enough gain so now he is all

I need to build something ASAP or at least suggest something to him thats a cheap solution. I really need something with 50m Ohm input impedance but most stuff only goes as high as 3m Ohm




here is what google has brought me, I like the first one cause its a TL071 and it seems to be simple and good design. I dont think these transistor designs are less than 20 years old.