PAFL level meters

[WolfgangParticipant]

Hello,

I’m sitting in front of a SQ6 and have connected a generator to Input1 (NTi MR-Pro)
This gives me a 1kHz signal with 0dBu level.

At the SQ I set the input-gaim to 0.
The displayed input level is exactly on the small black line in the level meter, so it shows 0dB.
So this is perfect.

All EQ and dynamics in the channel are switched to bypass.
And in each processor block, the level values in the display show exactly 0dB.

But now my question come:
– If I press the PAFL button on this channel, the LED chain next to the screen only shows -6dB.
Why is that?

And then the 2nd question:
– if I send this channel directly to the Main Mix (fader at 0dB) and the Main Mix fader is also at 0dB, then the Master PAFL level shows -9dB.
But the true level value at the output is 1.1dBu (with NTi XL2)
I don’t quite understand that either.

Can anyone help me how to read the PAFL meters or what kind of mistake I am making here?

Translated with http://www.DeepL.com/Translator

[jb07Participant]

I have just done the test, by sending locally on the ST1,a track with a signal set to 0db, the LCD meter is at the same level as the PAFL leds.
Or I read it wrong or translated it wrong.
France here.

[KeithJ A&HModerator]

Hi @wolfgang ,

The first thing to note here is that you are working with a mono input channel and a stereo mix (PAFL is like a very basic mix with no processing), so with some of your testing at least, the pan law could be in effect.
What you could do instead is patch your signal generator input to both sides of a stereo input channel and, as you are thinking only about levels at this point, imagine the whole setup as dual mono, then just concentrate on one side.

There is occasionally a question on average or peak measurement too (we use peak) so you could try the same test with white noise to check for any difference.

The LED indicators illuminate when the signal is equal to or above a value, so the 0dB LED’s show the level is somewhere above 0dB.
To test whether tiny differences in level are affecting your measurement, simply increase the level from your signal generator by it’s smallest increment.

Another thing to look at is your PAFL setup. For this testing, you probably want to switch both inputs and mixes to PFL (to remove faders from the equation) and ensure the PFL trim is at 0dB.

Hope this helps 🙂
Keith.

(as an aside, it would be interesting to know what you’re testing for too, or what you’ll be using the metering/PAFL to measure)

[volounteerParticipant]

@KeithJ A&H

But do you really display peak?
Or could their be real peaks, between the gaps in the times when you display a LED, that are higher.
Our device sure seems to us, at times, have been much higher than the LEDs just showed.

It would be nice to have a second set of LEDs that showed LUFs along with peaks.

[SteffenRParticipant]

But the true level value at the output is 1.1dBu (with NTi XL2)

that’s what I would expect (at least it is very close)
pan law decreases level by 3dB from a mono source to a stereo bus
0dB at the meters is +4dBu at the output

why it would show -9dB on the meters I don’t know

[WolfgangParticipant]

Hello Keith,
thanks for the quick feedback.

So if I consider the PAFL bus as a stereo mixbus, I can actually explain the -6dB values. If I add two identical sinus signals with the same phase position, I get 0dB.

On previous mixing consoles I could adjust the gain of the preamp by pressing the PFL to see the level at the preamplifier.
This is not possible here, because if you only display a mono signal, the display is 6dB too low.
Did I understand that correctly?
If yes: would there be a possibility to display only one LED chain for mono signals, but then display it with the correct level?

On the other hand, nobody has complained so far, so we can assume that my colleagues and I always leave enough headroom when adjusting the signal levels. 😉

[SmalldevelParticipant]

Hey,

But why does the change from AFL to PFL on the inputs affect another 3 to 6 dB PAFL change, when PAFL Bus is always stereo.

Thanks a lot

[SmalldevelParticipant]

Here a short video of the situation

[Mike CParticipant]

But why does the change from AFL to PFL on the inputs affect another 3 to 6 dB PAFL change, when PAFL Bus is always stereo.

Thanks a lot

Is all the channel processing set to flat and or bypassed?

[SmalldevelParticipant]

Yes, the console is completely resetted. That was the first doing on the console

[Flo84Participant]

Hi,
maybe A&H could add a user option to choose the measure point 🙂
Cheers

[KeithJ A&HModerator]

@smalldevel

But why does the change from AFL to PFL on the inputs affect another 3 to 6 dB PAFL change, when PAFL Bus is always stereo.

Because PFL is pre-pan (pan law not in effect) and AFL includes pan (pan law in effect).
Shown in the block diagram here – https://www.allen-heath.com/media/SQ_ReferenceGuide_V1_5_0.pdf#page=110&zoom=250,-76,585

Note that you will not see the same behaviour if you use a stereo input for this test, because stereo inputs to stereo outputs use balance, not pan.

@flo84
You can already choose what you send to PAFL and the 12 segment LED meter will always follow! 🙂
As well as PFL/AFL you can choose where PFL is sourced from, as described here – https://www.allen-heath.com/media/SQ_ReferenceGuide_V1_5_0.pdf#page=78&zoom=110,-439,18

Thanks,
Keith.

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