Calibrating Input Level for Plugins

[James Freeman]

Wait... -dBFS is Peak.
We need RMS.

Do you have any plugin that will show the average RMS value over time?

dpMeter5 is top notch and FREE.

dpMeter

dpMeter is free and a precise digital audio multi channel meter including RMS, EBU R 128, Dialog gated and TruePeak (intersample) measurement.

www.tbproaudio.de

 

[Orvillain]

Wait... -dBFS is Peak.
We need RMS.

Do you have any plugin that will show the average RMS value over time?

Can't think of a specific plugin off the top of my head, but setting the Reaper channel meters to stereo RMS mode, the figures are:
-108dB at 50% A/D sensitivity.
-104dB at 10% A/D sensitivity.
-102dBFS at 6% A/D sensitivity.

 

[James Freeman]

In most DAWs the meter setting will only change the meter behavior, not the numeric value you see on top of the meter, that's always peak.
For noise floor the Peak and RMS readings should be roughly 12dB apart.

 

[Orvillain]

Huh. Interestingly, I'm not convinced by the Reaper RMS metering. Here are some dpMeter5 screenies...

6% A/D sensitivity.

10% A/D sensitivity.

50% A/D sensitivity.

 

[Orvillain]

In most DAWs the meter setting will only change the meter behavior, not the numeric value you see on top of the meter, that's always peak.

Ahhhh. Well that explains it.

 

[James Freeman]

BTW, if you change mode to EBU you'll see LUFS, very handy plugin.
You also have various weightings (A,C, etc.) on the top right.

 

[Orvillain]

I just use ma ears bro

 

[DLC86]

We will never know until someone puts a sine tone through the Axe3 and give us a dBFS reading in DAW via USB.

I already did that for the fm9 a few pages back

 

[James Freeman]

I already did that for the fm9 a few pages back

Finally my new DMM was delivered so I measured my FM9 input. Feeding it a 1kHz sine wave at 1V rms I read -15.3 dBFS on the DI usb input, so that's what Fractal use as a reference voltage for their models, 6 dB lower than helix.

Oh, yea, you did.

FM3 is 17.7dBu (MirrorProfiles)
FM9 is 17.5dBu (DLC86)
Axe Fx 3 is 12.7dBu (Orvillain)

Which is weird, FM9 and AxeFx3 should have exactly the same input topology as far as I understand from reading the wiki.
Also, do the models sound the same with 5dB of gain difference?

 

[Orvillain]

Maybe I fucked something up.

 

[James Freeman]

Your test signal was a pure sine tone that you measured with a DVM?

 

[Orvillain]

Yep. Thinking about it, can't promise it was 1kHz. But DVM definitely measured 0.5v.

 

[pipelineaudio]

THIS is the type of stuff that needs to be done when people ask technical questions! Sad that the manufacturers never provide it.

 

[James Freeman]

The AxeFx wiki mentions this:

"The inputs can handle up to +18dBu. Use the Input Sensitivity controls to adjust accordingly." [43]

"The instrument input max voltage is about +/- 5.9V (11.8Vpp = about 17.5 dBu)."

But, when compensated digitally you actually have a FIXED internal dBu DI signal that the Models and DAW receive, this is what we are interested in.

The FM9 and FM3 have 0.2dB difference which is probably a small measuring error, but the AxeFx3 is a whole 5dB from the FM9... that's almost double the input voltage and will definitely affect the gain of the models.

 

[DLC86]

Yep. Thinking about it, can't promise it was 1kHz. But DVM definitely measured 0.5v.

You need to make sure your DMM can measure the voltage at that frequency, cuz a lot are made to be accurate only at 50/60 Hz.

AFAIK, the only way to route input 1 to SPDIF is to setup a preset that does this:

Btw, no need to setup up a preset like that, just select INPUT 1 right there

 

[DLC86]

The FM9 and FM3 have 0.2dB difference which is probably a small measuring error, but the AxeFx3 is a whole 5dB from the FM9... that's almost double the input voltage and will definitely affect the gain of the models.

I went from axe fx 3 to fm9 and didn't perceive any difference in tone in my presets, I'd say it's impossible there's a 5dB difference

 

[James Freeman]

True RMS DMV's can read accurately up to a frequency of 100kHz, non-True-RMS will have a limit of around 250 Hz and only accurate for pure sine tones.
Source

 

[James Freeman]

I went from axe fx 3 to fm9 and didn't perceive any difference in tone in my presets, I'd say it's impossible there's a 5dB difference

Ah, you have a Axe Fx 3.
You know what to do.

 

[DLC86]

I re-measured my fm9 via both usb and spdif

 

[DLC86]

Ah, you have a Axe Fx 3.
You know what to do.

Nope, I sold it a few months ago... but I seriously doubt there's any difference in that regard