I'm considering getting my 70D modded, but I want to get an idea of at least the self-noise of the stock unit. So, I did a quick test today, the best I could without any actual test equipment. If anyone with a modded unit would be willing to try the same test, I'd be curious to see the results.
All 4 channels recording at 24/48 BWAV, which is my normal recording format. Input set to MIC, but nothing connected so I would be recording silence / noise. Running off internal AAs.
I first recorded 3 sets of files (LOW, HIGH, and HIGH+ ranges) with the gain knobs at max for the worst-case scenario. I ran the resulting files through the Dynamic Range Meter plugin in Foobar to get the Peak and RMS values.
DR Peak RMS Duration Track
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DR7 -78.30 dB -85.82 dB 0:11 ?-01_LOW_MAX_150525_0016S12
DR7 -77.85 dB -85.97 dB 0:11 ?-01_LOW_MAX_150525_0016S34
DR10 -52.69 dB -64.63 dB 0:11 ?-02_HIGH_MAX_150525_0017S12
DR11 -53.17 dB -64.47 dB 0:11 ?-02_HIGH_MAX_150525_0017S34
DR10 -40.91 dB -52.64 dB 0:11 ?-03_HIGH+_MAX_150525_0018S12
DR10 -41.11 dB -52.51 dB 0:11 ?-03_HIGH+_MAX_150525_0018S34
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Next I did the same thing, with the knobs at zero:
DR Peak RMS Duration Track
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DR6 -80.13 dB -86.43 dB 0:11 ?-01_LOW_MIN_150525_0021S12
DR6 -80.25 dB -86.56 dB 0:11 ?-01_LOW_MIN_150525_0021S34
DR6 -80.38 dB -86.43 dB 0:11 ?-02_HIGH_MIN_150525_0020S12
DR6 -80.38 dB -86.56 dB 0:11 ?-02_HIGH_MIN_150525_0020S34
DR9 -74.87 dB -84.26 dB 0:11 ?-03_HIGH+_MIN_150525_0019S12
DR9 -75.58 dB -84.44 dB 0:11 ?-03_HIGH+_MIN_150525_0019S34
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I verified these numbers visually watching the meters in iZotope RX, and I took screenshots of the Channel 1/2 files which are below. (Channel 3/4 files essentially looked the same, and you can see from the numbers above they are within 0.5dB of the other two channels.)