New Firmware Update 1.21

[Guy Mcloughlin]

I did some quick tests of audio noise last night that I will publish next week once I’ve had a chance to test more cameras and recorders. Here’s how I test for audio noise:

1- Connect a Sound Devices mixer to camera/recorder ( I use a BeachTek passive adapter for devices that do not have XLR inputs ) using LINE level outputs.

2- Turn on the 1 Khz tone on the Sound Devices mixer, and adjust the recording level on the device ( camera or recorder ) so that the 1 Khz tone registers at -12 dB. ( -12 or -20 dB recording levels are standard when using digital devices because these devices do not have any headroom beyond 0 dB, so you are creating 12 / 20 dB headroom by recording at -12 or -20 dB )

3- Record the 1 Khz tone for 5 seconds, then turn off the tone while still recording for another 5 seconds.

4- Open the recorded audio file with a sound editor, and measure the sound level when the -12 dB tone is both on and off. You may need to adjust the volume of the audio file to ensure that the recorded tone is playing back at exactly -12 dB. The audio level measured when the tone is off should represent the actual noise-floor of the recording device under theoretically ideal conditions. ( in reality every mic has it’s own noise-floor, thus measuring in real-world conditions will vary greatly on how quiet the attached microphone is )

5- To test the mic pre-amps of the device, repeat the same steps but this time set the audio mixer to output a MIC level 1 Khz audio tone ( I use a -50 dB in-line PAD with the Sound Devices MixPre mixer ), and then use the built-in mic pre-amps of the device being tested to set the 1 Khz tone to -12 dB. With high quality mic pre-amps the noise-floor will be the same for both LINE level and MIC level tests.

…With my quick tests last night, both my Olympus LS-10 and HMC-150 showed a noise-floor around -60 dB for a LINE level signal, my Canon HG21 showed a noise-floor around -73 dB for a LINE level signal, and the Panasonic HS700 camera showed a noise-floor around -82 dB ( 22 dB lower than my HMC-150 )

I will publish all the results next week ( along with sample WAV files ) once I’ve had a chance to test more recorders. ( I want to add both Sony digital recorders and the Sony EX-1 camera )