OK dumb question…I just put a SuperVision instance set to VU on my master. Before that, I have a UAD Ampex tape plug in. So I see VU levels on the Ampex, and Supervision. The Ampex is reading normal levels (actually they were a bit hot and I trimmed the input to the AMPEX back a bit). Problem is as you can see in this screenshot, the VU meters in SuperVision are barely moving. Why is there a discrepancy between the two sets of VUs?
Different calibration of the VU meters. In supervision you can configure different scales for the display, and the default is “VU db”. If you set that to “VU dbFS” (with an “offset” of “-18”), it should be similar to the meter on the plugin, assuming that it is calibrated to 0VU=-18dbFS, too.
Is the signal going out of the track with the Ampex unchanged? I mean, you didn’t accidentally change the level between the output of the plugin and the input to supervision? And you are measuring the output in Ampex, right?
The default scale in Supervision is “VU dB”. Tbh, I am not sure what that even is, I mean, “dB” what? What reference level? The supervision manual just states “the scale allows you to select a scale according to different broadcast standards”., no more explanation. Maybe someone knows that the “VU db” scale in broadcast standards is.,
Switch the scale to “VU dBFS”, et voilà, same behavior as VUMT:
Interesting. I think the labeling is likely not very good here. It looks like the meter when set to default basically just makes -20VU the ‘reference’, and it then shows absolute level measured as VU. So it’s a 1-to-1 situation: an input of -6dBFS average will read -6VU on the meter.
When switching to VU dBFS the reference level is what you set using “offset” and it ‘shifts’ the entire scale accordingly, so that if you set it to -18 for example that same input signal of -6dBFS no longer “fits” on the scale. Since our “-18” = 0VU a signal of -6dBFS is far higher than the additional 3dB we have available above 0VU on the meter (because -6 is 12 hotter than -18).
So I suppose it’s a somewhat useful default if you want the ballistics of a VU meter but also want to see more of the signal. By this I mean that if you’re mixing a TV show for example and you need to hit -24LUFS (which is a sort of (average’) then using a ‘normal’ -18dBFS = 0VU calibration your meter headroom is only 9dB. Because you have 3dB above 0, and then you have (-24)-(-18) below that . So if your average is -24LUFS then all peaks at or above -15 will peg the meter far right. And if you have a loud passage where the average is about -18 for example then any peak 3dB louder than that will peg the meter. Not very useful. But if you’re using default the peaks all fit up to 0VU because that’s 0dBFS practically speaking. On the other hand your average signal will be below what the meter is showing since the lowest part is -20VU, not -24VU. Mixing for streaming with an average of -16LUFS for example might make sense though. You’d see that average and all peaks within the meter range.
But anyway… it makes sense but isn’t really labeled or explained that well.