Actually the internal mic preamplifier is adequately quiet enough, but the internal mics themselves are NOT. The noise you hear are from the mics and maybe their power source, NOT the deck's preamplifier as far as I can tell.
See updated review for external input spectal graphs for this deck at: www.sonicstudios.com/r-09revw.htm
Interesting....which ones should I be comparing I'm confused
Regards Scott
You're not the first to find this comparison confusing. All test were done with 1000 ohm dummy load at the inputs of R-09 mic jack and PA-3SX external preamplifier.
Best I can explain, the YELLOW trace is R-09 MIC input at 'HIGH" gain mode with REC level adjust setting at #22 (#30 is maximum) compared to best signal stage external preamplifier I know to design/build set at highest gain selection (PA-3SX external preamp is the green trace). For the deck's preamp set in high mode and #22 REC level, both internal and external preamplifier are applying the same gain to the MIC input with REC adjust set at #18 when external preamp is connected.
Under these conditions, if a mic was connected to either deck's mic input (the internal mic pre), or the external PA-3SX mic pre, the VU would read the same signal strength for identical loudness acoustic sound hitting the microphone, but the electrical input background noise (the electronics) would be at least 20 dB lower using the exteral preamplifier.
Obviously, the external preamplifier is going into the deck's LINE input, while the internal MIC preamp of the R-09 is working from the MIC input on the deck. In other words, for the same applied mic input gain, the green trace shows the recorded background noise with custom designed external preamplifier verses the yellow trace showing the background noise of the internal R-09 mic pre with all input conditions being equal.
Same type comparison is done again with RED trace showing deck's internal preamp now set in LOW mic input mode with REC level adjustment set this time at #30 maximum, and now compared to the VIOLET trace made with PA-3SX pre set at lowest (of three) gain settings with adjusting the deck REC level setting to #18 so input signal gain is again equal for internal/external inputs. This second set of traces (RED vs. Violet) shows at least 12 dB quieter input with the external preamplifier for equal applied mic input signal gain.
Even knowing much lower input noise is possible with special external preamp, the internal mic pre noise of the R-09 deck is NOT bad for general purpose recording with moderately high output microphones.