routed to ground via capacitor 226 which can be a a 0 01 microfarad capacitor output pin 6 is the gain setting pin which is routed back to pin 2 via variable resistor 228 which can be 1 megaohm low noise multiturn trim pot pin 7 is connected to the plus 12 volt input switch and is also routed to ground via capacitor 230 which can be a 0 01 microfarad capacitor the signal then travels from output pin 6 of amplifier 220 into output jack 232 after having been processed by an output switching network which is part of the input output switch shown in fig3 and 4 it is important to note that as the signal is passed through the various amplifiers in the low pass circuit the signal is initially inverted and finally returned to normal phase in amplifier 150 the signal entering through pin 5 is normal phase the signal entering pin 2 of amplifier 170 is inverted 180 degrees the signal entering pin 3 of amplifier 190 is not inverted and remains 180 degrees out of phase and also remains this way when it enters pin 3 of amplifier 214 the signal is returned to normal phase when it entered pin 2 of amplifier 220 this phase shift is necessary for the apparatus to work properly amplifier 220 has a gain of approximately 21 times the input signal the signal then passes to the gain setting network or attenuation circuit 32 the details of this attenuation circuit is shown at.