A gain of 70 db relates to an voltage gain of 3,162. If we take the square root of 3,162. Square root = 56.24. I would think a two stage amplifier with transistors is possible. If you use a common emitter circuit and let the unbypassed emitter resistor versis the collector resistor make the gain about 60 for each stage that should work. As the overall gain to A1 X A2. If the transistors have a minimum hfe of 100, it should work fine. Common transistors like 2N3904 may even work.