Hello all, I am designing a microphone preamp with some odd conditions. The microphone is dynamic. The impedance of the microphone is around 4 to 8 ohms (very odd mic, M-87/AIC). The goal is to interface the mic with a PC sound card which is designed to operate with an electret type. I have designed a circuit utilizing an op amp and an audio transformer. The circuit provides the desired gain and interfaces with the sound card appropriately, however the circuit has an annoying noise floor that I am trying to get rid of. The circuit features both high and low pass filters so it should eliminate any noise outside of the audible range which it seems to do when I put it on a scope. I also understand that a transformer will inherently pick up noise. However even with the transformer removed from the circuit there is still a white noise present. I have done a lot of reading and reduced my resistance values to do my best at eliminating resistor noise. I cannot quiet this thing down. I'm hoping you geniuses can guide me in the right direction. Some specs on the circuit; The op amp is a OPA2134PA VCC is +9vdc (currently a battery) I have added bypass capacitors to the op amp and the 'power supply' The gain is set to 201 (the mic is very low level) Here is the circuit Hopefully I didn't forget any pertinent information. Thank you for looking! any advice is appreciate.