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#9998 - 11/26/14 05:30 PM 2meter VU reads peak not RMS?
Leigh Offline
New Member

Registered: 11/26/14
Posts: 2
Loc: Portland, OR
Hello,

Didn't know where else to post this question. I just downloaded the 2Meters bundle, and I'm demoing it as an AAX on Pro Tools 10/Mac OS 10.8.5.

In short, I'm not seeing the meter read the way I would expect it to. I am seeing peak values on the meter, not RMS values. Is this intentional?

To reproduce, set up a Signal Generator plug-in, for a 1k sine, level -10dB, and the "PEAK" (not "RMS") level setting. That means that the Signal Generator's output signal is hitting a peak of -10dBFS, and the RMS value (for a sine wave) is 3dB lower, at -13dBFS.

However, when I put a PSP VU2 meter on it, and calibrate it to a 0dBFS reference, the VU meter reads -10dB, NOT -13dB.

Again, my question is: is this the intended behavior? Every real-world VU meter out there reads RMS, not Peak, and I thought it was the idea of this plug-in to emulate a hardware VU meter.

Thank you,
Leigh

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#10002 - 11/27/14 04:20 AM Re: 2meter VU reads peak not RMS? [Re: Leigh]
Adam Taborowski Offline
Member

Registered: 11/27/14
Posts: 4
Hello !

The behavior of PSP 2Meters bundle is intentional. VU meter reads the volume units - not RMS.

If the signal generator is set up at -12 dBFS - and the both meters (VU and PPM) have reference level at -12dBFS - the needle should show 0dB.

Best Regards,
Adam Taborowski

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#10003 - 11/28/14 03:41 PM Re: 2meter VU reads peak not RMS? [Re: Adam Taborowski]
Leigh Offline
New Member

Registered: 11/26/14
Posts: 2
Loc: Portland, OR
Adam: Thank you for the reply, but your answer is not completely clear.

Originally Posted By: Adam Taborowski
VU meter reads the volume units - not RMS.


"Volume units" and "RMS" are not somehow mututally exclusive. Indeed, the technical definition of a VU meter is:

Quote:
The reading of the volume indicator shall be 0 VU when it is connected to an AC voltage equal to 1.228 Volts RMS across a 600 ohm resistance (equal to +4 [dBu]) at 1000 cycles per second.


Of course, since this is a digital implementation of a VU meter, we can ignore the "600 ohms resistance" part of the definition. But regardless, "volts" are equivalent here to digital amplitude, and 0 VU = 1.2V RMS, not 1.2V peak.


Originally Posted By: Adam Taborowski
If the signal generator is set up at -12 dBFS - and the both meters (VU and PPM) have reference level at -12dBFS - the needle should show 0dB.


Would this be with the signal generator set for -12dBFS peak or 12dBFS RMS?

Thank you,
Leigh

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#10004 - 12/01/14 09:15 AM Re: 2meter VU reads peak not RMS? [Re: Leigh]
Adam Taborowski Offline
Member

Registered: 11/27/14
Posts: 4
Dear Leigh,

We always calibrate meters to peak sinus in digital world. We have to remember that digital requirements are different from analog world. VU internal level should be -18, but if converter has level lower than +22dBu for 0dBFS - internal level in VU will be different. For converter that is reaching level about+18dBu (for 0dBFS) internal level should be -14dBFS.
You can always change meter calibration on the back panel of plugin to be sure that the meter responds to your needs. The ballistics of the needle is a true simulation of typical VU meters (but even here you can switch between A/B type, because we have found that many analog meters had little differences in the way of needles' motion).

Best Regards,
Adam

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