Wouldn't adding a pre-amp to the chain result in even higher levels at the r09? A simple 1/8 to 1/8 inline attenuator would be inexpensive insurance to have on hand.
You should not have any issue running a preamp into the r-09 when your using the line input. The r-09 can handle very high input levels on the line input.
"Should" doesn't mean much when you come home with a trashed recording. This isn't about high levels but heavy bass. When you take into account that the r09 often distorts below setting 8, it doesn't have such great high level signal handling capability. It is possible that the AT853 bass response is insufficiently low to cause this problem in the r09.
I've run the v3, aerco and eaa psp2 into the r09 many times behind Schoeps (mk21 & mk4) and Gefells. The first time I noticed it was on Geoerge Porter Jr's bass with stage lip mk21's. I don't run any stinkin bass rolloff. I doubt there would be a problem if the bass is neutered before it reaches the r09.
Maybe you have recorded with the r09 at low trim settings in intensive bass situations and had a difference experience. But if you haven't, you should make it clear that you are just speculating.
On the r-09 the distortion percentage changes by maybe 1.50% on frequency.. Meaning its got a pretty liner distortion curve. I would suggest if your having distortion issues its not because your feeding the R-09 with "too much bass" its because your signal is too hot... Anything over 0db when the gain is set to 6 Is going to cause problems. If it was a really bad device we would expect to see more of a change but we do not. Its pretty smooth.
Here are my measurements on frequency based on a unity gain input of 0db in at level setting 6
20hz THD+N = 1.23% THD = 0.64%
30hz THD+N = 1.22% THD = 0.641%
40hz THD+N = 0.9% THD = 0.83%
50hz THD+N = 0.7% THD = 0.62%
60hz THD+N = 0.5% THD = 0.44%
70hz THD+N = 0.19% THD= 0.05%
100hz THD+N = 0.11% THD= 0.03%
1000hz THD+N = 0.02% THD= 0.02%
From this we can conclude that distortion does change with frequency but as I said its very little change and I am not sure anyone could hear it. And that was with the gain control set to 6 and my test analyser set to 0db out.
I suppose someone could argue that this is a distortion test not a listening test, and well that would be true but I would say if you can hear the difference in distortion between 0.04% and 0.9% you have bat ears.
Imo this device is fine feeding it any kind of signal as long as you dont go over 0db at its input. I would suggest running this thing at about -6db total signal input max for headroom. And of course that depends on the setting on the r-09. But I found that at the #6 level setting this product could easily handle 0db input.
I would suggest that using a preamp on the front end is not any more likely to increase distortion on bass or any other part of the frequency response, then using the built in preamp would. If the max input level is exceeded its exceeded and distortion will happen.
When you take into account that most mics ( my CA-11 or AT mics ) even at a very loud concert are going to be producing a level of -29 ( if they have my mod ) or are three wire ) or so and my preamp provides 20db of gain and most people actually only use 75% of the gain from my preamp or 15db. The signal the recorder would be seeing would be somewhere in the neighbourhood of
-15db That means the recorder only has to provide +10db or so of gain to provide a 5-6db of headroom in your recorder more then a safe amount.
BTW there is no speculation going on here. I have measured it and run it with out issues. Its not a frequency related problem its a gain related problem. IF you set the level to high on the r-09 you will have issues. With any preamp.. But if your careful you will not.
Chris