Hi All,
This is a good discussion relevant to my current project also. I can add that I have used a single channel RESP file from another station and easily modified it for my instrument. There is a web page at http://ds.iris.edu/ds/nodes/dmc/data/formats/resp/ explaining the format and also the relation to SAC pole zero format. Depending on the situation, I found I could roll the sensitivity numbers together and end up with only one or two stages comparable to a SAC pole zero format. If you do not need the decimation filters the end result can be quite simple with only poles and zeroes, AO normalization, and the final sensitivity.
I am currently creating a read function for PSN format files. The format can contain poles and zeros and sensitivity in various header sections. My goal would be to gather the bits and load them directly into a usable structure such as the station inventory but I am also struggling with deciding if it is worth all the code to create the entire inventory object or just allow a user to load a simpler format dictionary as shown using poles and zeros in the simulate or pazToFreqResp examples.
Randy