Topic: Microtrack TRS input levels and metering questions

[raddygast]

Ok, I bit the bullet and bought two high-end (well, high-end for me, but basically low-end broadcast grade) microphones.

I got two Audio Technica AT-831b miniature unidirectional cardioid lavalier mics. These come with a battery pack so I don't need to deal with phantom power issues.

Anyway, the mics seem to sound great for my application (interview-type, but both my voice and the speaker's voice need to be high enough fidelity for me to do speech and accent analysis afterwards).

The only problem is the levels. I'm using some heavy-duty XLR-to-balanced-TRS cables, and I thought these mics would be "hot" enough that I'd be able to use the "M" switch on the Microtrack recorder, with some fiddling of the levels.

Unfortunately, everything is quiet. Even with the levels set to max, and the switch on the side set to "H", the recording is still quiet. I can yell at the top of my lungs and not get clipping, and speaking at a clear but normal volume the levels only ever get a bit past "half", judging from the LCD meters.

I have had to resort to using the 27dB TRS boost from the "Record Settings" menu. With that option on, I set the switch to "M", and set recording levels to be just slightly over halfway. That gives me decent levels, though it still sounds quieter than most of the music/audio/etc. I play back on my computer (i.e. when I transfer the WAV to my computer and play it back with the same computer volume settings, it's quieter).

I'd like to raise the levels a bit but then I start to get clipping when someone speaks loudly.

My mic question is, am I doing something wrong? Aren't these mics supposed to be good? Why would they be so quiet -- is it a mic preamp thing? Is the Microtrack recorder just not very good at amplification? Is the 27dB "digital boost" an extremely horrible thing to resort to?

Also, regarding the LCD level meter. What is it supposed to mean? I understand the triangles, and the level bars, but what are those little notches that appear and then disappear? Judging from my experience with graphic equalizers, that should probably show peaks, esp. since they seem to disappear after a few seconds of no signal. BUT... the level bars and the peaks seem totally out of sync or at worst unrelated. For example, I sometimes see the levels reaching up to about halfway, and sometimes going healthily over, but the peak notches are usually another third of the way up. When I get clipping, for example (red LED), I notice the peak notches are at max, but the levels at that instant are quite a bit shy of the maximum.

Is it just a lag problem? Because I think the microtrack isn't even showing them on the same scale. I've never seen the level bars all the way up, but I've seen plenty of clipping and maxed out peak notches. What's going on?

[Nick Graham]

Nothing you do at home (yelling, stereo, etc.) will come anywhere close to the SPL of a concert, you should be fine.

Have you updated to the latest firmware? That fxed most known problems with the levels/metering.

[keepongoin]

My mic question is, am I doing something wrong? Aren't these mics supposed to be good? Why would they be so quiet -- is it a mic preamp thing? Is the Microtrack recorder just not very good at amplification? Is the 27dB "digital boost" an extremely horrible thing to resort to?

i don't think you are doing anything wrong.   the mics are probably designed for higher volume sounds than talking.  the preamps in the microtracker are not that great, but i don't think the 27 dB boost is horrible to use either... it gets you levels, right?  it is better than no levels.  you should aim to have them as high as you can without clipping - you can always add gain later with software, but you can't really fix clipping-related distortion.

Also, regarding the LCD level meter. What is it supposed to mean? I understand the triangles, and the level bars, but what are those little notches that appear and then disappear? Judging from my experience with graphic equalizers, that should probably show peaks, esp. since they seem to disappear after a few seconds of no signal. BUT... the level bars and the peaks seem totally out of sync or at worst unrelated. For example, I sometimes see the levels reaching up to about halfway, and sometimes going healthily over, but the peak notches are usually another third of the way up. When I get clipping, for example (red LED), I notice the peak notches are at max, but the levels at that instant are quite a bit shy of the maximum.

Is it just a lag problem? Because I think the microtrack isn't even showing them on the same scale. I've never seen the level bars all the way up, but I've seen plenty of clipping and maxed out peak notches. What's going on?

not 100% sure what you are asking... they are level meters... and they go haywire after some period... as nick mentioned, the new firmware does wonders for this part of the functionality.

[raddygast]

Ok, thanks for the info.

But to clarify what I meant by the levels -- first off, yes, I have the newest firmware.  Second, what I was describing (badly) is this:

The levels sort of work like this:

L: ================-----|--------
R: ==============------|----------

where I'd expect this:

L: ====================|----
R: =================|----------

I mean this only at an actual peak.  Normal level behaviour (from equalizers) is that the meters rise and fall, and the little notch thing represents the most recent level peak over a certain sliding window of time. Some equalizers have the peak notches "decay", and some simply let them exist for a few seconds until replaced by a higher peak notch, or until a delay expires.

On the microtrack, however, I see the peak notches are always consistently higher than where I see the levels rise to. So the diagram on top may be the highest I see the levels go -- but the peak notch acts as if the levels went that much higher.

Does that make sense?

[keepongoin]

makes more sense now.  maybe you aren't seeing it because you aren't watching it the whole time, or maybe it goes up that far for a split second, long enough to register on it, but not long enough for the peak meters to show up.

i am just glad that the V3 has good level meters.

[raddygast]

What is this V3 I keep hearing about? Is it a preamp?

[keepongoin]

pre-amp and analog to digital converter. 

http://www.gracedesign.com/products/V3/lunatecV3.htm

[Zaphod Beeblebrox]

Raddygast,

On my Sound Devices 442 the top mark on the scale denotes the peak level and the lower marks are the VU levels.  I don't know if that's what M-Audio intended or not.

Also, could someone please point me to the appropriate thread if this question has already been answered, but I'm wondering if anyone knows if M-Audio has any intentions of numbering their meters with a typical digital scale so that we know where -20dB or -12dB are on their segmented scale?  I think it would be a nice feature so that we know how much headroom is available as well as when calibrating with other devices.

-Zaphod

[udovdh]

See this for dB values.

[Zaphod Beeblebrox]

Thanks for the info.  It helps a lot.

-Zaphod

[branas]

I wondered the same thing about the level peaks and the indicated levels below it. I assumed that it displays the peaks accurately, but the current levels are less accurate because it is an lcd display and I'm not sure, it may be a processor speed limitation or something. I went with the assumption that the peaks were correct and everything came out fine.

[raddygast]

Yeah, that's exactly my point. Everyone seems to be saying the metering is fixed now on the MT, but it isn't. I don't think it's an LCD updating thing, because the peaks are displaying rapidly. It's just the actual meter isn't sampled fast enough, perhaps, to catch the peaks.

OR maybe the meter bars represent averages, not a dynamic real-time account of the level. So if they are sampled every 0.25 secs, they display what the average level was in that interval, whereas the peak will display any and all peaks that come along.

It's annoying though.

[Craig T]

OR maybe the meter bars represent averages, not a dynamic real-time account of the level.

bingo.

[cmoorevt]

raddygast-  that site udovdh linked is very helpful with metering issues. it takes a little bit of time to get thru it all, but there is a lot of good info there.

re: the averaging, see the attached image.

fwiw, I've had very good luck watching the average level and ignoring everything else.

[raddygast]

Well, the behaviour of the meters now makes sense, but not of the engineers. Isn't it abnormal to have the bars represent averages? On every mixing board or graphic equalizer I've seen before (even on computer media players), the peaks are what's left behind by the bar in realtime. The bars oscillate wildly, and when a peak is left if you watch carefully it is always left by a bar that just went beyond the previous peak.

Maybe they designed it this way because the LCD is too slow? But then how come the peaks are fine?

Anyway, I'm just going to try and set levels so the peaks get as close to the edge as possible without clipping.