I have just checked and the track peaks at about -9dbs and is generally at about -12dbs when I am talking. I remember reading somewhere that for dialogue peaks at -6dbs were a pretty good level, so I did not feel like the recording was that quiet. I also recorded using 24 bits of resolution, which my understanding is that it allows pulling up quite a bit without too much trouble.
With lower cost consumer grade recorders ( tascam are consumer grade, but you can get good results with them ) the base noise-floor of the recorder is usually in the -50 to -75 dB RMS range, where professional gear usually has a noise-floor of -100 dB RMS or better. When you set a recording level of -12 you are using that top 12 dB to act as your digital "headroom" and anything below this -12 dB is the dynamic range of your recording. If you have to boost your recording in post because the mic was badly placed or the speaker is very quiet, then you are going to lose even more of your recording's dynamic range. When you've run out of dynamic range, all that is left is noise.
There's a simple test you can do with your recorder and lav, and a 3.5mm audio extension. ( assuming your lav has a 3.5mm plug on the end )
1- Place your lav in the spot you want it ( i.e. middle of sternum ), plug it into your recorder and then adjust your recorder's level until your normal speaking voice is peaking at -12 dB.
2- Unplug your lav mic and plug in the 3.5mm audio extension ( the extension should be less than 10 feet long, or it may cause it's own audio problems )
3- Start recording at the SAME level you had set for your lav mic. ( you are recording "silence", but you will soon find out how silent this is ) Record for 20 seconds.
4- Transfer your "silence" audio recording to your computer and using your audio editor's level meter ( I use the Sound Forge RMS level meter ) see what the audio level is for your "silence" recording. With a good recorder you should be seeing a noise-floor of -70 dB or better. ( pro gear is often around -100 dB RMS )
This will give you a clear idea of the noise-floor of your recorder when set to the recording level you would use with your lav mic. You can't make a noise-free recording if your recorder is already pretty noisy.
My old Canon 60D camera had a noise-floor of -52 dB when tested this way, and it sounded like there was a sand-storm in the background.
Where my Panasonic GH5 shows a noise-floor of -73 dB RMS and is very quiet when set up correctly.
I own five Tascam recorders, and all of them show a noise floor between -70 dB to -75 dB RMS.
Consumer recorders have pretty noisy pre-amps, so you want to match them with "hot" mics that put out a strong signal, so you end up using as little gain as possible.



