I agree with Sean, I think an SD MixPre would match well with the NT4 and R09. The hiss you heard when running NT4 > R09 is probably because you were applying gain (amplification) to the NT4 using the R09. The R09 doesn't have a lot of clean gain. Using the MixPre, or another suitable preamp with lots of clean gain, should remove the hiss.
The click concerns me, though. Any chance you can post an MP3 sample? Could be an NT4 battery, cable, or R-09 input connector issue. If the NT4 worked okay with the Zoom, it's probably not an NT4 battery issue (unless you didn't use battery power with the zoom, and switched to phantom power; in which case the issue could still be the NT4 battery power). To narrow it down further, assuming you have access to some additional gear, test running
NT4 > known-good interconnect cable > R-09, and
NT4 > known-good interconnect cable > another recording device that accepts the mini-stereo jack. The goal is to isolate each piece of gear in the recording chain to see if the problem follows a specific piece of gear.
As for the Oade MOD FR-2LE, I think you'd want the Super MOD for nature / ambient (unamplified source) recording. This will provide higher gain than the Basic MOD. But it's also another $150. I can't compare sound quality directly to the MixPre > R-09 / Zoom, but do have a couple general comments:
- The NT4 > FR-2LE combo should prove more robust physically, mainly due to more secure (XLR) cable connections. The R-09's mini-stereo connector isn't the most secure / robust connector in the world.
- Purpose-built devices generally provide better quality. The NT4 > MixPre > recorder option may provide more gain, at higher quality, than the FR-2LE.
There's the conundrum: do you want a setup (NT4 > FR-2LE) that's more robust and still sounds mighty good, or a slightly more purpose-built setup (NT4 > MixPre > R-09) that's not as robust, but may offer slightly more / cleaner gain? Given the wealth of reasonably inexpensive, reasonably high quality gear available these days, I'm inclined to keep it simple. That would lead me to NT4 > FR-2LE, stock, Basic, or Super, depending on your needs and budget.
You might consider calling Doug Oade or sending him an email similar to what you've posted here and pick his brain a bit. I'm a big fan of Oade modded gear, and he may have some good input for you. One thing to keep in mind: at least historically, Doug has allowed me to send back my preamp/ADC/recorder for a MOD upgrade. So, for example, if you don't have the cash up front for the Super MOD FR-2LE, you could go with the Basic MOD (or stock unit) for now, then send it back later and have it upgraded. (
Note: If you buy a stock unit, you must buy it from Oade Bros, otherwise I don't think they'll upgrade it later.) It's a bit more expensive doing it in multiple steps, but it might provide a nice, compact, robust field recording setup now, while also allowing you the option of higher / cleaner gain down the road by simply sending it back for a Basic or Super MOD, without a lot of hassle, changing up of gear, etc.
Oh, and welcome to TS!