As stated before, the gain of this circuit is (R43+R14)/R26 = 101K/1K. This produces a gain of 101, not 1100. The combination of C34 and R43+R14 makes a low pass filter at about 1/(2pi*R43+R14) = 1/(6.23*1e-9*101e3) = 1.6KHz. The combination of R26 and C14 makes a high pass filter of 1/(2pi*0.1e-6*1e3) = 1.6KHz. There is a low pass filter coupled with a high pass filter at the same frequency, makes a band pass filter at 1.6KHz. Pspice model of the circuit shows a gain of 63 at 1.6KHz. Because the low pass and high pass filters interfere with each other, the gain cannot reach the theoretical value of 101. The "soft clamp" introduced by the back-to-back diodes across R14 does almost nothing because the diodes action across 1K from a total of 101K is a very small effect. If the diodes were across R43 on the other hand, they would have a lot more leverage on the performance of the circuit.
Gil

 

Welcome to the forum Gilbert and I hope you stay active, what an introduction

 

As stated before, the gain of this circuit is (R43+R14)/R26 = 101K/1K. This produces a gain of 101, not 1100. The combination of C34 and R43+R14 makes a low pass filter at about 1/(2pi*R43+R14) = 1/(6.23*1e-9*101e3) = 1.6KHz. The combination of R26 and C14 makes a high pass filter of 1/(2pi*0.1e-6*1e3) = 1.6KHz. There is a low pass filter coupled with a high pass filter at the same frequency, makes a band pass filter at 1.6KHz. Pspice model of the circuit shows a gain of 63 at 1.6KHz. Because the low pass and high pass filters interfere with each other, the gain cannot reach the theoretical value of 101. The "soft clamp" introduced by the back-to-back diodes across R14 does almost nothing because the diodes action across 1K from a total of 101K is a very small effect. If the diodes were across R43 on the other hand, they would have a lot more leverage on the performance of the circuit.
Gil

Thanks Gilbert. R14 is 1M, not 1K. I hadn't noticed the low pass and high pass filters so good to know.
Ron