"Input clipping"-like Issue When Picking Hard

levipeto said:
With only an input and an output block on the grid, I get + 7-10 dB clipping

I have turn the instrument input level almost all the way down.
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Where? At out 1? Input to Output block Does clip for me always. It shows a healthy level is being fed into the amp block typically there.
 
To the original poster. I posted about the same thing a while back. On my real Fender amps if the amp is set clean and I hit the strings harder it just gets louder. It doesn't go into distortion like the Axe FX. I found the only way I can get totally clean sounds with the Fenders in the Axe FX is to turn the input trim down about half way, and not have the amp set any higher than 3 or 4. Only then I can get totally clean sounds when digging in with the pick. I am using an Eric Johnson Strat with stock pickups, and a 54 Strat with stock pickups, so the pickups are not real hot. I'm playing through Yamaha HS8's also.
 
Moke said:
Hmmm. That doesn't sound anything as extreme as what I am getting. But in my case it is most likely exaggerated because of increased treble in my Acoustic Sim presets.
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Even in the AX8 days, I sometimes had this issue with acoustic sims (both yours and my own - and even worse presets for acoustic with piezo). If there is not amp block, and the IR is boosting some frequencies a lot, I often hear some crackling going on. I always thought, it was the very dynamic transients that clipped somewhere.
 
chris said:
Where? At out 1? Input to Output block Does clip for me always. It shows a healthy level is being fed into the amp block typically there.
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Whaaaat?? That shouldn't be like that?? I never tested this - I have to try for myself :)
 
shorerider said:
I managed to record a snippet of what I'm talking about.
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this actually doesn't sound abnormal to me. simply lowering the gain slightly, or putting a compressor in front of the amp to tame the dynamic peaks would probably sort it. do you normally pick that hard when playing?
i have my deluxe gain set to 4 for use with single coils (which are actually stacked humbuckers) and it's right on the edge of distorting when i pick as hard as i can, or play chords with a bridge humbucker. in the normal run of things, i never hit it that hard.
 
trancegodz said:
To the original poster. I posted about the same thing a while back. On my real Fender amps if the amp is set clean and I hit the strings harder it just gets louder. It doesn't go into distortion like the Axe FX. I found the only way I can get totally clean sounds with the Fenders in the Axe FX is to turn the input trim down about half way, and not have the amp set any higher than 3 or 4. Only then I can get totally clean sounds when digging in with the pick. I am using an Eric Johnson Strat with stock pickups, and a 54 Strat with stock pickups, so the pickups are not real hot. I'm playing through Yamaha HS8's also.
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I wonder if this has to do with the fact that we're adjusting our input sensitivity to "tickle the red"? Because some single coils need the input sensitivity pushed up to 100, and hot humbuckers end up being down around 10%, and we're optimizing for strong signal with low noise maybe what we're also doing is ensuring that the guitar signal is always "loud". On a real rig you don't have this level adjustment step so when you go to single coils into your fender in the real world you're sending way less signal, but in Axe land it's being normalized in volume compared to high output humbuckers.

So maybe the issue is just this: your guitar in the Axe is acting like an idealized super guitar that outputs a loud clear signal no matter the pickup output level. And if you want to hit the front of the amp with a low signal turning down input trim is actually the right way to do it.

simeon said:
yup. mine peaks at 7db. i wouldn't neccessarily call it "clipping" though."level" might be a better word. yes, it's in the red, but i don't hear any distortion
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I wonder if this is also related to the input SNR adjustment. Since your signal is supposed to "tickle the red", does that actually mean your signal will go above 0dB and into the red portion of the meters inside the axe too. It kind of makes sense.
 
IronSean said:
I wonder if this has to do with the fact that we're adjusting our input sensitivity to "tickle the red"? Because some single coils need the input sensitivity pushed up to 100, and hot humbuckers end up being down around 10%, and we're optimizing for strong signal with low noise maybe what we're also doing is ensuring that the guitar signal is always "loud". On a real rig you don't have this level adjustment step so when you go to single coils into your fender in the real world you're sending way less signal, but in Axe land it's being normalized in volume compared to high output humbuckers.

So maybe the issue is just this: your guitar in the Axe is acting like an idealized super guitar that outputs a loud clear signal no matter the pickup output level. And if you want to hit the front of the amp with a low signal turning down input trim is actually the right way to do it.



I wonder if this is also related to the input SNR adjustment. Since your signal is supposed to "tickle the red", does that actually mean your signal will go above 0dB and into the red portion of the meters inside the axe too. It kind of makes sense.
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You're fundamentally misunderstanding the way the input sensitivity works.
 
FractalAudio said:
You're fundamentally misunderstanding the way the input sensitivity works.
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Very possible. To try and say it another way, my idea right now is this:

You're standing in front of a Fender amp with a low output single coil strat, and a high output humbucker-loaded Les Paul. If you measure the transient sizes of either you get (made up values) 1.5V on the strat, and 4.5V on the LP.

When you plug into your fender, you are either sending it 1.5 V or 4.5 V depending on the guitar, for heavy picked transients. The amp's topology, gain staging, and settings configure how that behaves, but you're lilkely to start clipping (overloading one of the tubes, and getting distortion) sooner with your higher output pickups. As they are outputting about 3x the voltage swing.

Now you plug into your Axe Fx III, and you adjust the input sensitivity. Here you're adjusting the range that the ADCs listen at to get the largest signal compared to noise. For your LP, you adjust it so that it can read +/-5 V, to tickle the red on your transients, and in the strat you adjust it to +/- 2 V to do the same.

The end result is that inside the Axe FX III, both guitars, after adjusting sensitivity, are outputting a signal of about unity gain (0 dB, or maybe higher/lower in practice, but similar to each other for the purposes of this thought process). And now both of these signals are entering the Fender amp model at unity gain, and where before your 3x amplitude voltage swing lead to some sort of decreased headroom, now both signals are sending at a similar amplitude.

But I do remember reading that the input sensitivity is configured in such a way that it doesn't increase input signal, it just reduces noise floor, so maybe that is my fundamental misunderstanding.

And if that's the case, my question becomes: does that mechanism still preserve was was originally a 3x difference in transient amplitudes, or does it equalize them to a degree, and therefore start feeding the amp models with larger signal than they get in reality, leading to people getting preamp distortion at levels lower than they're used to getting in the real world.

Or are they just not used to being able to hear the sound clinically through headphones and recorded because normally they'd be at stage volume.
 
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IronSean said:
But I do remember reading that the input sensitivity is configured in such a way that it doesn't increase input signal, it just reduces noise floor, so maybe that is my fundamental misunderstanding.
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Correct; the pre-AD level changes are countered by an inverse gain adjustment immediately post-AD. Lower actual output level from guitar = lower level entering grid from input block.
 
My understanding is that as long as you are not clipping at the DA or AD converters, there's pretty much no way to clip the signal on the grid unless it's designed to do so like in the amp block, drive block, etc. Calculations on the grid are floating point so there's pretty much unlimited headroom between blocks. The 24 bit, 114 dB dynamic range only applies at the converters and over USB and SPDIF.
 
IronSean said:
Or are they just not used to being able to hear the sound clinically through headphones and recorded because normally they'd be at stage volume.
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I think this is a lot of it. Cranking something like a Twin Reverb up to the point it starts to break up is usually painfully loud. Unless you have your Axe FX cranked up that loud as well, the experience is going to be quite different. You might find yourself noticing a lot more subtle detail in the sound because you are not as distracted by the sheer volume rattling your teeth.
 
IronSean said:
And if that's the case, my question becomes: does that mechanism still preserve was was originally a 3x difference in transient amplitudes
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Yes, actually fractal devices afaik are the only ones doing this right in preserving the original guitar signal level.
If you boost by, let's say, 6dB pre-conversion it automatically attenuates it by 6dB post-conversion.
Every other modeler or digital device I've tried only has a normal input gain adjustment which just boosts/attenuates the signal pre-conversion, that tends to make you set every guitar roughly at the same level.
That's not necessarily a con though.
 
The litmus test for any modeler is whether adjusting that input level has any noticeable affect on the tone produced. If the amp models clip a lot more when the input trim is turned up, that's bad. You are losing much of the dynamic character of the instrument. Vintage single coils and high output humbuckers should absolutely not drive the amp with the same level. That is a deal breaker.
 
IronSean said:
Now you plug into your Axe Fx III, and you adjust the input sensitivity. Here you're adjusting the range that the ADCs listen at to get the largest signal compared to noise. For your LP, you adjust it so that it can read +/-5 V, to tickle the red on your transients, and in the strat you adjust it to +/- 2 V to do the same.

The end result is that inside the Axe FX III, both guitars, after adjusting sensitivity, are outputting a signal of about unity gain (0 dB, or maybe higher/lower in practice, but similar to each other for the purposes of this thought process).
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You have indeed re-stated your misunderstanding in a different way. ;)

I think you're missing the fact that as you pad the input to the converter, the output of the converter is boosted accordingly, so guitars of different levels -- even with different input settings -- reach the grid/amp model at different levels, with results just as if you plugged them alternatingly into the same patch cord connected to the same tube amp.
 
The Input sensitivity control works like a see-saw. On one side you have your input padding and on the other side you have your inverse cut/boost that happens immediately after AD conversion.

Turn Input Sensitivity up: BOOST your guitar's analog signal going into the Axe, WHILE ALSO CUTTING IT an equal amount after AD conversion.
Turn Input Sensitivity down: CUT your guitar's analog signal going into the Axe, WHILE ALSO BOOSTING IT an equal amount after AD conversion.

This means the Axe will always see the the correct actual volume of a guitar, while also allowing you to adjust for the best guitar input signal-to-noise ratio.

One potential opportunity for misunderstanding is that you only see one value of the two values you're actually changing with a single control. I wonder if it would be more clear to people if the value read something like "Input -5 db, internal compensation +5 db" or something like that.
 
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IronSean said:
Or are they just not used to being able to hear the sound clinically through headphones and recorded because normally they'd be at stage volume.
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THAT, is the right answer. I challenge anyone to prove that the models don't clip the same as the real amps. Put your amp in isolation or use a load box and then do an A/B test with the model. You'll be surprised. It's a far different experience playing through an amp when it is right next to you. Our hearing is nonlinear and logarithmic so when playing very loud all these fine details are masked.
 
FractalAudio said:
...Put your amp in isolation or use a load box and then do an A/B test with the model. You'll be surprised. It's a far different experience playing through an amp when it is right next to you. Our hearing is nonlinear and logarithmic so when playing very loud all these fine details are masked.
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There it is, the inconvenient truth.

Amp Purist: Why is the Axe-Fx with FRFR different from amp-in-the-room/at-the-gig?

Fractal Audio: It's different because...(pauses, contemplates the billion frikken conversations about this)...because it's different!

Some players achieve the difference-leap on day one. Some take years to do so. And some are biased and/or bewildered forevermore.
 
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