Calibrating Input Level for Plugins

[James Freeman]

You have a "mV" setting on your Multimeter.
Check if it is sensitive to frequency, it should read the same mV of frequencies up to 1kHz, above that the reading is not accurate.

 

[MirrorProfiles]

You have a "mV" setting on your Multimeter.
Check if it is sensitive to frequency, it should read the same mV of frequencies up to 1kHz, above that the reading is not accurate.

just noticed my Signal generator was set to peak rather than RMS. The signal out of the D/A through the reamp box and DI match though. Here it is at RMS. It IS changing Voltage when I change frequency though when set to V or mV



Green is the D/A output, Purple is the DI input



EDIT: Running this signal into FM-3 In1 gives exactly what I was getting earlier

 

[James Freeman]

It IS changing Voltage when I change frequency though when set to V or mV

Alright, just find at what frequency your DVM reads the highest mV value and doesn't drop. My DVM reads the same mV value from 20Hz to 1kHz and drops from there.

+16dBu is 4.887v RMS.
+20dBu is 7.746v RMS.
I don't understand how the FM3 clips with just 0.5v.

 

[MirrorProfiles]

Looks like around 1900Hz I get the highest readings. 1900Hz=637.5mVAC here. Shall I drop that signal down to 500mV and try again?

btw, I just remembered my reamp box has a tone control on it, so that may be why the readings were changing with frequency.

FWIW, I set it to 1900Hz (-20.285dB in PT). This gives an output on the FM-3 of +9dB.

Adjusting these doesn't seem to have any effect either.

 

[James Freeman]

I'm not sure why your DVM is doing that, it supposed to be True RMS.
Nah, no need to change from 400Hz, just keep using that specific DVM with all your measurements of output voltage, we are calibrating to relative -dBFS readings anyway so the actual voltage you use is not very important as long as you keep using it.
But not if we are doing math, when doing math true voltage reading is important.

Found why Output 1 is clipping with only 500mV at input, because you are using Output 1 at -10dBV setting.
If so, use Output 2 mode with "Unity Gain" setting, and turn the panel volume knob to max, to get accurate dB reading.
You can verify that by reading the mV at the Output 2 (Send) of your FM3.

 

[MirrorProfiles]

use Output 2 mode with "Unity Gain" setting, and turn the panel volume knob to max, to get accurate dB reading.
You can verify that by reading the mV at the Output 2 (Send) of your FM3.

Setting Out 2 to Unity Gain and -10dBV gives this.

Input signal:



FM-3 Screen (this is going unbalanced from the reamp box into In1):



Measured output out of Output 2 set to max:



and as an aside, recalibrated the reamp box level for unity with a flatter EQ curve:

 

[MirrorProfiles]

and now, setting my Line Output for 500mVAC going into input 2 gives this:

 

[James Freeman]

1900Hz

24th fret on the E string is 1320Hz (330Hz*4, two octaves).
The average center of frequencies of electric guitar is between 100 to 400Hz, stick to that range.
Anyway.

Measured output out of Output 2 set to max:

Okay good.
Please use a mono cable (unbalanced) if you want to match FX Return to Guitar Input, I don't know if the FM3 compensates for that.
Post the dB difference.

PS.
Gotta say, it is still weird that 500mV is hitting orange at the input LEDs.
Looks like the the Input +16dBu spec is with the 18db Pad enabled, without it you have -2dBu of headroom which is only 0.615v.

 

[MirrorProfiles]

electric guitar is between 100 to 400Hz, stick to that range

Yeah all the above measurements were back at 400Hz

Changing both In1 and 2 pad's to 18dB puts them both at the orange LED. They're both equal at orange at all pad settings except for 0dB where it hits red.

Looks like it automatically compensates the output as that remains at -31.5dB throughout.

 

[James Freeman]

I'm still a bit lost on what to do next .

Both Input 1 and 2 display the same -dB value at the output?
Post the dB readings when you run the signal into Input 1 and 2.

 

[James Freeman]

Changing both In1 and 2 pad's to 18dB puts them both at the orange LED. They're both equal at orange at all pad settings except for 0dB where it hits red.

Weird again, any EMG would clip the shit out of that.

 

[MirrorProfiles]

Both Input 1 and 2 display the same -dB value at the output?
Post the dB readings when you run the signal into Input 1 and 2.

Input 1 (unbalanced 500mV):



Input 2 (same unbalanced 500mV):



Input 2 (balanced 500mV signal):



I'm confused here, because it looks like I have them matched the same when using the line input with balanced cables. If I were to reamp like this, I'm pretty sure it would sound like I'm slamming the input way too hard. My default was to set the Input trim to around 0.5 and then thing would behave more like my amps.

 

[JiveTurkey]

Tag Cliff and see if he can provide some insight?

 

[James Freeman]

I'm confused here, because it looks like I have them matched the same when using the line input with balanced cables.

It appears so, but we have no idea if the balanced signal is further manipulated before an amp block.
The meter shows the same output db but it is still 6db hotter when going into the amp.... a real mystery.

Input trim to around 0.5

If the input trim is linear, 0.5 is -6db, so everything checks out.

 

[James Freeman]

Tag Cliff and see if he can provide some insight?

Where's the fun in that?

 

[MirrorProfiles]

If the input trim is linear, 0.5 is -6db, so everything checks out.

The only thing I don't understand is what you said above - perhaps the amp block is lowering the instrument input by 6dB more than when a line input is used.

I suppose I could reamp a signal through the balanced line input, and input 1 and 2 with unbalanced instrument cables and see if I hear a difference. There's a chance I might have become a full blown alcoholic at that point though.

 

[James Freeman]

The only thing I don't understand is what you said above - perhaps the amp block is lowering the instrument input by 6dB more than when a line input is used.

Use a clean amp with low gain, like a Fender Twin or something.
That is a straight forward answer, you should see the same input sine wave with some 2nd and 3rd tube harmonic.

 

[MirrorProfiles]

Use a clean amp with low gain, like a Fender Twin or something.
That is a straight forward answer, you should see the same input sine wave with some 2nd and 3rd tube harmonic.

will give this a go later on. Nice one for the help, always useful to learn more about how all this gear is working and doing it this way kind of taught more.

Legend.

 

[James Freeman]

My pleasure.

Welp, it's back to trolling for me.

 

[pipelineaudio]

How do you match master volume settings between amps in helix. I have been trying like hell to get Panama to sound like vitriol, as Panama uses piles less dsp but I am totally stuck. I think it’s a master volume or bias or biasx problem but I can’t crack it.