What you'll see in the graphic below is that the Juno-G(and all Fantom Engines for that matter) actually filter the output of samples. It's came up in quite a few threads that Roland adds preemphasis to their internal samples. If you are using external samples, or resampling, preemphasis is required if you want to hear the same sound using the audio outs.
The conclusion I've come to is that the output filter is very close to a 6db lowpass @ 12khz. It's slightly less nearing 20khz and drops off progressively more above that, but I don't have a filter less than 6db to test.
The interesting, and slightly troubling, thing I discovered is that adding preemphasis, while virtually restoring the frequencies perfectly(7-10k), does inadvertently create a high shelf almost 5db higher @ 20khz when compared to the original. It most likely would be EQ'd out in production, but without that and multiple samples could add up to quite a sheen in those extreme frequencies.
The filtering below 30hz can also be noticed, but is mostly beneficial.
(Note: These tests are certainly not the most scientific. I did not go to the extent of precisely aligning levels and the graphic is a composite of many takes, but the general idea should be clear enough.)
