I don't think there are any gear with 20K input impedance... so I would use the lower value of 560mV at 2K load. That's more realistic.
thanks, that actually jives better with my observations
By my logic, with a close to 900mV output from the mic, the mic would reach its max spl of 134 dB somewhere between FSD and -10 dB
If I understand your sentence right, you're looking at this backwards and equating apples to oranges.
The max SPL of the mic is the loudest level it can be subjected to. (And note that 130dB is 10dB more than the threshold of hearing pain, 120dB. )
134dB SPL is not the output level of the mic. The mic will never "reach" this 130dB SPL.
SPL = sound pressure level. The max SPL the mic can withstand... NOT the mic can reach.
yes i understand that. My point was that the (lack of) gain strategy allows for the full range of the mic, and that the mic would suffer input distortion before the rest of the signal chain.
the noise on your recording will be the same regardless of if you are recording at 0db or -30 dB and post-normalizing.
No, it's not the same.
Normalizing will multiply by a factor of X both the signal and noise. Your overall volume level may be up, but your dynamic range is still the same if you normalize it.
Amplifying the signal while keeping noise down not only increases your volume level but also your dynamic range. This is not something "normalizing" can give you. If it did, all pro recording engineers out there will be normalizing instead of working hard to reduce noise.
i have to disagree with you on this one For this example, im going to refer to the self-noise spec of the mic as opposed to dynamic range, please correct me if im wrong in any assumptions here.) Ok here goes. The signal coming off the mic is what it is. The noise coming off the mic is what it is. These are in a fixed ratio (maybe not ratio, but fixed dBA difference lets say) This is why placement is so important, to get the highest level possible into your mic and keep the noise down. The noise level of the mic relative to the input signal is entirely independent of ANYTHING you put downstream. Lets assume my source has a maximum volume level of 100 dBA (typical not-too-loud concert environment) and the mic noise is 18 dBA . If i use a preamp and record with peaks at 0dB, the self noise of the mic is at -80 dB. If i dont use a preamp, and my peaks are at -30, the self noise of the mics is recorded at -110 dB. When normalizing, you amplify the following three signal (or noise) levels):
1. peaks get normalized from -30 to 0 dB
2. self noise of mic gets amplified from -110 to -80 dB (the same as if you had used a preamp for gain)
3. self noise of the A/D gets amplified from -117 dBA to -87 dBA (inaudible? relative to mic noise)
4. the 'quantization noise'? (digital noise floor, LSB, whatever) gets amplified from -144 dB to -114 dB and subbsequently dithered - absolutely inaudible
With this setup, no matter what you do, i beleive it is impossible to create additional audible noise that wouldnt be masked from the mics in the first place. in other words, regardless of what gain you use, if your having noise problems, its because the volume of your source wasnt high enough and the self noise of your mic is controlling. i have tried to hear the noise floor of he ad2k, i cannot distinguish it from the noise floor of the mics themselves.
Lets take an extreme case: peaking at -70 dB vs using 70 dB of gain in the field - all youre gonna hear is predominantly the noise of the mic, and thats a mic placement issue, entirely independent of signal chain - 'garbage in, garbage out.
Earlier you said, but its only 16bit, and wouldn't have the headroom to pull this off.
I think you meant to say "dynamic range."
As 16 bit will only have 96dB dynamic range, well below the 120dB dynamic range of human hearing.
Headroom has got nothing to do with 16 or 24 bits or dynamic range. Headroom is NOT THE SAME as Dynamic range.
"Headroom" is the maximum voltage level that your gear can work with without clipping, and is measured in dBu (note the "u", it's not just dB). Where 0dBu = 0.775Vrms = 2.45Vpp
thanks, yes i was speaking of dynamic range. i kno wim not the first one to brutally use those words interchangably