I'm designing a product using a couple of these preamps. I have them in a custom dev board now and for the most part things are fine. However, I've discovered that need all of the features of this device EXCEPT the noise gate. I understand the concept of having one there, and at first I thought it would be a good thing. My problem is that some of the signal levels coming in from the WL93 subminiature condenser mic are so small that i guess it's close to the noise floor of the preamp. This application requires me to pick up ambient noise in the room, not just high sound pressure levels like I would get if it were being used to mic someone speaking directly into it. I tried 5K and even 10K resistors on the gate pin but they killed the ambient levels I need to get.
I like the expansion/compression performance of the device and when i take the gate resistor completely off pin 7 it lets everything in the background through nicely. I'm concerned because the datasheet advises against using anything over a 5K resistor because "The noise floor of the SSM2167 prevents the noise gate from being lowered further without causing problems". I am also getting some pumping noise presumably from the level detector capacitor at times as well. Is there any way to effectively and reliably turn off the noise gate/level detector of this device? I have not started playing with different values of level detector caps yet.. I have some on order.
Have you looked at the SSM2166? This preamp is similar to the SSM2167, but is a bit more flexible. Specifically, its noise gate threshold can be set to a lower point, between 300 uV rms and 20 mV rms …