Topic: I managed to overload my FR-AV2 mini-jack mic input with a pair of Clippy mics

[TheJez]

Just to share my experience...
Earlier this year I got a Tascam FR-AV2 and a pair of Clippy microphones (EM272M capsules) with 3.5mm mini-jack connector. The main goal was to get less-noisier recordings for more quiet shows than I was able to create previously with an Edirol R09HR with a pair of Core Sound Stealth Cardioids.
I was very pleased with the result, regarding getting rid of noise as well as the richness of the sound. I was very impressed with the sound of the Clippies v.s. their price.
Next up: A loud rock show! Because I was pleased with the result of the more quiet recording, I wanted to give the Clippies a chance. As I knew these were less suited for very loud music, I knew there would be a risk. But how loud is 'very loud'? It is not 'Extremely loud', right? 'Just to make sure to be able to deal with the high SPL, I built my own 9V battery box to power the mics. (Just in case the 5V PIP of the Tascam wouldn't be enough.)
I was standing about 2m (~7ft) from a filler speaker at the side of the stage, 'record level' to 0dB so I would see the real levels of what comes out of the ADC's on the VU meters without any digital amplification. Very soon into the first song, I noticed that the VU-bars on the recorder were completely red, which means that the analog input is overloaded. The bars still went back and forth a bit, though, so not constantly pushed to their max. Anyway, not good :-(. I had to move away from the PA quite a bit to make the VU bars color 'normal'. Unfortunately, there I picked up far more crowd noise than I wished for, so all in all it turned out to be one of my worst recordings ever.
Back home, I decided to do some math (which I could have and should have done before instead of after the show), with some help of AI, as I'm not very good at that and always find the dBV's, dBU's, Pa's and whatever very confusing...:
- The Clippies / EM272 have a sensitivity of ~40mV/Pa
- Max SPL of the EM272 is ~122dB
- Max input of mini-jack mic input of the FRAV2 is +1 dBV, which is apparently ~ 1.122V
With 40mV/Pa sensitivy, we would need about 123 dB SPL to get a voltage of 1.122V. So apparently I had to deal with a SPL of more than 123 dB as the analog input was overloaded! To be honest, this surprises me. I was thinking that the SPL at the show was lower. Yes, it was loud (especially near the speaker), but was it that loud?? Or did I miscalculate somewhere?
Anyway, I have been thinking of ways to deal with this better in the future, e.g.:
- Use/build an attenuator of e.g. -6dB or -10dB), so I can make sure that the output of the mics won't overload the analog input?
- Build a 3.5mm-to-2xXLR connector so I can connect my (unbalanced) Clippy mics to the XLR inputs? Not sure if this as such would help, though, as the max input of the XLR input (when configured as mic-in) is +4 dBU, which is apparently 0.975 V, which is lower than the 1.122V of the mini-jack input! (). Or maybe set to line-in, so the max input would be +24V, which is apparently 12.3V, which would be way too high for the Clippy mics.
And, regardless, apparently loud concerts can easily reach the max SPL of the mics themselves anyway, so whatever tricks done after the mics will not prevent the distortion by the mics themselves.
So the bottom-line is that I just need some less sensitive mics for loud shows. I may revert to the Core Sound's or try to get some other mics.
Maybe someone more math-savy can double-check my observations and conclusions. Any comment is welcome.
Otherwise I just put this here to share my experience, so others won't make the same mistake as I did...

[Joop]

I was standing about 2m (~7ft) from a filler speaker at the side of the stage, 'record level' to 0dB so I would see the real levels of what comes out of the ADC's on the VU meters without any digital amplification. Very soon into the first song, I noticed that the VU-bars on the recorder were completely red, which means that the analog input is overloaded.

This is the first strange thing in reading. Why set record level to 0dB? In your case -20dB would do perfectly.

Yes, it was loud (especially near the speaker), but was it that loud?? Or did I miscalculate somewhere?

Yes,unfortunately lots of stage folks still think that loud is some kind of quality. It is not, next; how about your ears? That kind of volume is good for only about 1.5 second per day listening before damaging your ears! (based on 80dBspl 8hours, 3dB up half that time).

There is almost no difference between XLR or 3.5mm with mic use, except that XLR is phantom power and 3.5mm does have PIP. So your calculation is wrong. The maximum input on XLR is +4dBu and that is 1.227652988V (site Sengpielaudio), so its a little more than max. 3.5mm input. Setting things to line will switch off phantom power or PIP,  because there are not such equipment which need that.

Clipping is still possible, the marker is the +4dBu which seems to pop up in every spec with double ADC's. Yes, it is possible to overload the input with the Clippy's.

So start with a record level of -20dB (-18dB (Default) recommended in the manual), the noise floor is sufficient low for getting that in the way.

[datbrad]

The FR-AV2 manual lists the max signal for the 1/8" unbalanced input to be +1 dBV, so you definitely need a lower sensitivity microphone. You might want to consider the DPA 4099s, they are only 6 mv/PA, and I think they have a version coming out soon that is only 2 mv/PA.