DAW digital peak and VU meters not matching analog realm meters, maybe?

[cashhewn]

Hi,

I’ve calibrated my hybrid system so that a sine wave in a DAW track that peaks at -14dBfs comes out of the converter and hits the LED meter of a channel on my analog console at just below the red, and I’ve labeled that with P-touch tape as -14dBfs on the console meter and it corresponds to 0VU on the mix bus measuring about 1.23Vrms…all well and good I think.

However, when I send a non-sinudoidal signal, say a kick drum, in this same way the peak tick mark in the DAW meter might get up to (making these numbers up now) -10dBfs and the body of the signal/VU bar stays down around -20dBfs, the corresponding LED meter in the analog console channel does not match either of these figures…if I recall correctly it might read another 10 dB lower.

I know that my console channel meters can be set via internal jumpers to either peak or VU, and I haven’t pulled them out to check the jumpers yet, but I figured I could deduce what they’re set to probably without doing so.

Is it that the “ballistics” of these LED analog meters are simply different so that they respond identically to the digital realm with a sine wave but very differently to a transient rich signal?

Thanks for your help.

[Wonks]

The VU meters can only be accurately calibrated across different outboard equipment with a sine signal. Analogue VU meters all respond slightly differently to other signals, so you should expect some variation in meters on different units.

And the meter itself is averaging the signal over a short period of time, so it’s indicating an average power level, not a peak one like a standard DAW meter.

A sine wave has a constant power level, a few dB below the peak value, (so it’s great for calibration purposes) but a dynamic music signal can have an average power level a lot below the peak level. Or very heavily compressed music might have an average value only just less than peak.

So don’t expect a VU meter to tell you the same thing as a DAW peak meter.

[Hugh Robjohns]

I’ve calibrated my hybrid system so that a sine wave in a DAW track that peaks at -14dBfs comes out of the converter and hits the LED meter of a channel on my analog console at just below the red...

"Just below the red" isn't a meaningful signal level.

...it corresponds to 0VU on the mix bus....

Ah! That's a little more helpful. 0VU is intended to indicate the standard operating level (or alignment level... ) Let's assume "just below the red" also equates to the operating level through the channel — 0VU, again.

...measuring about 1.23Vrms…all well and good I think.

Indeed. So you calibrated your analogue/digital alignment for -14dBFS = +4dBu (0VU). Why didn't you just say that?

However, when I send a non-sinudoidal signal, say a kick drum, in this same way the peak tick mark in the DAW meter might get up to (making these numbers up now) -10dBfs and the body of the signal/VU bar stays down around -20dBfs, the corresponding LED meter in the analog console channel does not match either of these figures…if I recall correctly it might read another 10 dB lower.

Yes... they would do that. These are perfectly normal meter behaviours. You need to read up on what an analogue VU meter indicates compared to a digital sample peak meter.... or an analogue peak meter.

I know that my console channel meters can be set via internal jumpers to either peak or VU, and I haven’t pulled them out to check the jumpers yet, but I figured I could deduce what they’re set to probably without doing so.

Well, the required information is certainly there in your post.... I'll place my money on VU.

Is it that the “ballistics” of these LED analog meters are simply different so that they respond identically to the digital realm with a sine wave but very differently to a transient rich signal?

A constant steady sine wave makes differing meter ballistics irrelevant and, being a sine wave, the crest factor is known so the level will indicate the same on both peak and rms (VU) meter scales. This is obviously essential for system line up calibration.

But on varying music signals the meter type and ballistics will give very different dynamic readings, especially with transient signals and with different frequency content. This is completely intentional.

[cashhewn]

Thank you Mr. Robjohns.

Indeed. So you calibrated your analogue/digital alignment for -14dBFS = +4dBu (0VU). Why didn't you just say that?

Probably because my insecurity due to my relative inexperience has me still doubting even the fundamental foundations of my setup! So I kind of waffle on hoping that my explanation will reveal whether or not I’m “doing it right”.

Right, so in summary we can deduce that the console meter jumpers are not set to peak since they are not hitting the same absolute level as the DAW peak meters, and since the console meter is reading program material lower than the DAW VU meter then we can deduce that there are different ballistics laws at play between the DAW VU and the console VU meters.

Hope that’s about right. Thanks Hugh!

[Hugh Robjohns]