Sending AxeFX input to Plugins - what's the correct input level?

[MirrorProfiles]

Thanks - I'll try a MM measurement. Wrt Amplitube, that's what I was afraid of as mentioned above: their individual models might be varying wrt to reference input level, and if that's the case and they've lost track, it makes me lose confidence in their level of diligence with respect to accuracy - IK fixing and/or clarifying would be a confidence rebooster to me.

Yep, same here. There is quite a lot that IK get right and then they seem to shoot themselves in the foot. I’ve tried a LOT to make progress on this and it’s fallen on deaf ears. I suspect they won’t acknowledge this until it’s fixed rather than publicly admitting anything. Which sucks for users but it’s how IK want to do things, and it is what it is.

I've always just used USB 5/6 on the Axe FX III as the input into NDSP plugins. I have the signal/noise ratio on my Axe FX so it isn't clipping (10% in my case with active pickups). Is there something else you should be doing in addition to these steps?

If you want the most accurate gain response from the plugins, then yeah, you’ll want to know exactly what headroom this reaches the DAW with. I can try and measure later, essentially it’s a case of running a known voltage sine wave into the DI input at given settings and noting what level it appears in the DAW as. It’s likely that it’ll need some amount of boost or cut to match precisely.

 

[Orvillain]

His whole premise seems to be "we were all told to set the gain on our interfaces as high as possible without clipping," but I've never heard that advice in my life. Everything I've heard has been to shoot for -18 to -12 or so.

Actually, it gets said a lot by guitar centric people who believe themselves to be audio engineers of some kind. I've heard it countless times over the last 16 years since I started in the industry.

The other thing people often say is to aim for -18dBFS to -12dBFS, as you've just said. But there isn't actually very much behind that other than the assumption that old analog ways of working apply to the digital realm. It isn't always true.

a lot of plugins normalize on -18 dB FS nominal level

Please reword this. Because it reads poorly. Plugins do not normalize to a specific input level. They might expect a nominal input level, but they don't actually do anything to your signal until you turn the knobs to tell it to do so. Or at least they shouldn't. If they do, they're probably a poorly implemented plugin.

 

[sprint]

However, there has always been the problem in the digital amp modeler world that it's difficult to share presets among people with different guitars. I may have a nice high-gain preset that I want to share with you, but if your guitar has different output pickups or setup than me, it may sound weird to you, no matter how we calibrate our audio interfaces. In other words, in order to facilitate preset sharing, it would be better to normalize on the plugin input level, not the audio interface. The goal here is to get our presets to sound similar, not our rigs. That way you can play your guitar through my preset and get the same kind of gain in the tone that I intended when I created the preset. Some plugins have a built-in normalization feature for just this reason. In this scenario, audio interface input gain is adjusted solely to optimize S/N.

IMHO, I wouldn't say anybody is missing the point. There are just two different things one might be trying to achieve when normalizing input levels.

+1 that preset sharing with different guitars is a different and separate consideration from input calibrations. Imo, the way to deal with preset sharing is to always share a DI also as I've advocated for here many times. As we know well, guitars (even different instances of the same model guitar) don't sound the same, and even the same instance of a specific guitar won't sound the same in different hands. If all shared presets were always accompanied by matching DI and output clip samples from the preset sharer, the "why don't I sound the same on the same preset" issue could pretty much be resolved since the preset sharee would always have the tools to reproduce locally, the exact sounds they heard from the sharer, and be able to work out the exact reasons for the delta in sound (not the least of which might be that the sharee's similar guitar has differences (electronics, pups, setup ...) or, that he/she simply doesn't have the skill level yet to play the material in exactly the same way) - the only remaining equalizer, would be making sure the input calibrations as discussed here, are matched (easier to do when sharing hardware based modeller presets than when sharing plugin based presets due to the reference calibration uncertainties mentioned above). What I see happening here over and over again is preset sharees' immediately latching on to suspicions of modeller hardware or firmware problems as the likely reason for the differences they hear - they latch on to that, when i'd bet, in most cases: guitar/hands (+ maybe input calibration in the case of plugin presets) is the actual culprit which gets largely ignored in sherees' quests.

 

[weird guitar person]

Please reword this. Because it reads poorly. Plugins do not normalize to a specific input level. They might expect a nominal input level, but they don't actually do anything to your signal until you turn the knobs to tell it to do so. Or at least they shouldn't. If they do, they're probably a poorly implemented plugin.

Fair enough. I've reworded it. I'm sure there will be issues with the rewrite. Set your normal levels, then start pushing into the model if you wish. Not dissimilar to the way the Axe-Fx is set up. The main point was don't assume that plugins model a particular input level. In Cordy's vid, the problem was that folks were hitting things super hot, and the levels talked about were still relatively hot compared to what a lot of plugins expect.

 

[GuitarGuy316]

Yep, same here. There is quite a lot that IK get right and then they seem to shoot themselves in the foot. I’ve tried a LOT to make progress on this and it’s fallen on deaf ears. I suspect they won’t acknowledge this until it’s fixed rather than publicly admitting anything. Which sucks for users but it’s how IK want to do things, and it is what it is.



If you want the most accurate gain response from the plugins, then yeah, you’ll want to know exactly what headroom this reaches the DAW with. I can try and measure later, essentially it’s a case of running a known voltage sine wave into the DI input at given settings and noting what level it appears in the DAW as. It’s likely that it’ll need some amount of boost or cut to match precisely.

Sure, I think a lot of us use the USB inputs so I’d be curious to know what you measure. Are you changing the output inside of the Axe FX or the plugin itself?

 

[MirrorProfiles]

Sure, I think a lot of us use the USB inputs so I’d be curious to know what you measure. Are you changing the output inside of the Axe FX or the plugin itself?

I dont use the Axe FX as a DI input for recording, I normally use a different chain. But I'll measure anyway. But yeah, you can adjust levels wherever you like, the main thing is knowing how much headroom you have so you are able to accurate adjust it based on what you are using. You could record at 16dBu and boost 3.8dB in the plugin, or you could record 3.8dB hotter, or you could run a trim plugin in front of the amp sim boosting 3.8.

 

[MirrorProfiles]

for USB recording via Input 5/6

0.707V RMS into instrument input 1 gives me:

10-95% A/D Sensitivity=-18.2dBFS=17.4dBu
100% A/D Sensitivity= -20.1dBFS=19.3dBu

Between 95% and 100% it moves towards 19.3dBu. Presumably the signal that reaches the DAW will generally be 17.4dBu except if you have it in that range.

 

[Chromatizm]

I was always wondering why my Zoom interface allows sound through when the Input gain knob is at 0. I though it was some kind of weird bug but didn't care cause I always used to set the knob to be "close to clipping", and never bonded with any plugin at all.

Now I understand this is exactly the position I should use to get proper input level from software plugins when plugging directly into the interface. This seems like the "-12dB" position or something close to it
I'm using NAM while waiting for FM3T to arrive, and only once I set the Input gain on Zoom to zero, someone's Shiva's profile started sounding close to what I'm used to with Fractal (with CabLab as IR loader, cause build-in loader sounds like garbage can).

 

[sprint]

Yep, same here. There is quite a lot that IK get right and then they seem to shoot themselves in the foot. I’ve tried a LOT to make progress on this and it’s fallen on deaf ears. I suspect they won’t acknowledge this until it’s fixed rather than publicly admitting anything. Which sucks for users but it’s how IK want to do things, and it is what it is.

Regardless, Amplitube is still my preferred amp sim overall. Even if the "reference level" is varying by model, just publishing the that reference level for each model would provide what's needed to match what the author intended / what's most authentic.

 

[MirrorProfiles]

Regardless, Amplitube is still my preferred amp sim overall. Even if the "reference level" is varying by model, just publishing the that reference level for each model would provide what's needed to match what the author intended / what's most authentic.

Yeah, if they could just give the information then at least you’d have an idea of what their reference amp sounds like and how the model is supposed to behave. A lot seem to be 0dBu or -3dBu, so definitely be prepared to boost a lot in AT. The slash boost is just a clean level and is quite handy as it goes beyond the input slider (which is needed). Also means you can blend amps with different calibrations

 

[TGM]

for USB recording via Input 5/6

0.707V RMS into instrument input 1 gives me:

10-95% A/D Sensitivity=-18.2dBFS=17.4dBu
100% A/D Sensitivity= -20.1dBFS=19.3dBu

Between 95% and 100% it moves towards 19.3dBu. Presumably the signal that reaches the DAW will generally be 17.4dBu except if you have it in that range.

Glenn Friecker has occasionally mentioned that AXE FX DI level is low(compared to what, I have no idea). I also tried AXE fx with many plugins and I always had to increase the input gain on the plugins. So is this the primary reason? Man, I've been wondering about this for a long time now.

If I got it right, for NDSP plugins, I need to apply around 5.2 dBus of gain. Where is the best place to apply this, on the plugin itself? Or is it better to do it via a parameter on the AXE?

By the way, I've been a fan of your youtube content for a long time now @MirrorProfiles. Great great work.

 

[MirrorProfiles]

Glenn Friecker has occasionally mentioned that AXE FX DI level is low(compared to what, I have no idea). I also tried AXE fx with many plugins and I always had to increase the input gain on the plugins. So is this the primary reason? Man, I've been wondering about this for a long time now.

If I got it right, for NDSP plugins, I need to apply around 5.2 dBus of gain. Where is the best place to apply this, on the plugin itself? Or is it better to do it via a parameter on the AXE?

By the way, I've been a fan of your youtube content for a long time now @MirrorProfiles. Great great work.

Basically yeah. I wouldn’t say it’s low but it’s also going to be a good few dB below clipping so probably more dynamic than what a lot of people might dial in with a preamp.

But yeah. Just add the amount of gain you need in the plugin. That’s exactly what the input adjustment is for - to remove the variable of different converter reference levels

and thanks!

 

[MackieFX]

If the DI on the Axe is low, does that mean its a really bad idea to track a DI with the Axe???

 

[MirrorProfiles]

If the DI on the Axe is low, does that mean it’s a really bad idea to track a DI with the Axe???

It’s an ideal level already, just boost in the plugin. It’s an excellent choice to use as a front end for plugins.

It’s not “Low” it’s just “lower than some people might record with even though there is no benefit to recording hotter”

 

[weird guitar person]

If the DI on the Axe is low, does that mean its a really bad idea to track a DI with the Axe???

No! It's a great idea to track a DI with the AxeFx!

If you know the [reference level] of the guitar plugin use a trim control or plugin in the box to bring it up [to that].

 

[MirrorProfiles]

expected average input level of the guitar

this is a little misleading - the signal level of the guitar isn’t actually relevant, the goal isn’t to compensate for different guitars being different levels.

The gain adjustment is so that the amount of headroom is calibrated. If we’re measuring the average level of guitar, then quiet pickups get normalised to the same level as loud ones and we end up in this bad situation where amp sims sound wrong.

A sine wave is used for that reason (and why things like dBu and voltage are mentioned in these discussions) - it’s a constant voltage that can apply universally to measure stuff. Guitars fluctuate loads in level and frequency so aren’t really a good way of measuring anything.

 

[scarbodave]

this is a little misleading - the signal level of the guitar isn’t actually relevant, the goal isn’t to compensate for different guitars being different levels.

The gain adjustment is so that the amount of headroom is calibrated. If we’re measuring the average level of guitar, then quiet pickups get normalised to the same level as loud ones and we end up in this bad situation where amp sims sound wrong.

A sine wave is used for that reason (and why things like dBu and voltage are mentioned in these discussions) - it’s a constant voltage that can apply universally to measure stuff. Guitars fluctuate loads in level and frequency so aren’t really a good way of measuring anything.

I think the complete phrase was "average input level of the guitar plug-in". Maybe not the best choice of words but I took this to mean the reference level of the plug-in (eg. 0 dBFS = 12.2 dBu). If the FX3 has 0 dBFS= 18 dBu then use the gain/trim in the plug-in to adjust for the difference.

 

[weird guitar person]

this is a little misleading - the signal level of the guitar isn’t actually relevant, the goal isn’t to compensate for different guitars being different levels.

The gain adjustment is so that the amount of headroom is calibrated. If we’re measuring the average level of guitar, then quiet pickups get normalised to the same level as loud ones and we end up in this bad situation where amp sims sound wrong.

A sine wave is used for that reason (and why things like dBu and voltage are mentioned in these discussions) - it’s a constant voltage that can apply universally to measure stuff. Guitars fluctuate loads in level and frequency so aren’t really a good way of measuring anything.

I've a 64 input interface and 45 years recording experience. I'm simplifying because some of this discussion is arguably in the weeds.

 

[MirrorProfiles]

I think the complete phrase was "average input level of the guitar plug-in". Not the best choice of words but I took this to mean the reference level of the plug-in (eg. 0 dBFS = 12.2 dBu). If the FX3 has 0 dBFS= 18 dBu then use the gain/trim in the plug-in to adjust for the difference.

Yeah, I'm just being slightly nitpicky because the biggest hurdle for people seems to be that they're thinking in terms of the guitar signal rather than the headroom of what they're plugging into.

Its been amended now so its much clearer so all good

 

[MackieFX]

Im just thinking in terms of tell me what f*&^n knobs to turn and stop posting the maths