Handle the resistor carefully. The oily film of your hands will easily affect the resistance. The third key component is a metal die cast box. Don't waste your time with sheet metal boxes from Radio Shack, or worse yet, plastic boxes and copper tape. The fourth key component is a pair of 9 Volt transistor radio batteries, mounted inside the box.
Dead bugs are the fifth key component.
OK, I'm having some fun. The operational amplifier can be socketed, but the actual input lead should be pried up and connected so as to float in mid air. This circuit is deceptively simple. The most important parameters affecting it's performance are the construction details.