Distortion characteristic of decaying notes is chattering

[davebode]

I just bought a Helix LT as a replacement for my HR MX5. When comparing amp models with the same IR I am noticing that the Helix has this odd behavior on any overdriven/distorted amp. As the notes decay there is a chattering that happens on the upper harmonics. In other words the higher frequency noise doesn't fade away smoothly as the note does. Instead, it kind of chatters like a gate or noise filter when the input is right at the threshold.

I also compared this to a tube amp and tweaked the settings to sound pretty close. Check out the demo. The examples are Headrush AC HI BOOST (Celestion IR), Helix A30 Fawn Brt (Celestion IR), and Peavey Bravo 112 recorded with a Beta57A. I didn't fuss with the positioning of the mic on the Peavey.

 

I would reckon they sound pretty similar. The thing that is bugging me is the distortion decay on the Helix. It comes on and decays rather abruptly and I think I know why. Going back and forth between the Headrush and the Helix and then the Peavey I noticed something. The Headrush and Peavey have a background hiss when the preamp gain is up and the Helix doesn't. Is this some kind of Magic? No.

I think what is happening is that there is some kind of noise filter that is processing the upper harmonics/distortion noise separately from a lower overdriven amp sound on the Helix. As the input envelop starts to decay, it starts increasing the noise reduction/gate threshold and that's why it chatters. It does the same thing on the attacks of notes to some degree. The decay of the upper harmonics/noise on the Peavey  is a little smoother and I don't hear them cut off abruptly like the Helix does. The Headrush also has a smooth decay of the harmonics. To me the Headrush is a bit smoother than this particular Peavey amp, but it's more preferable than the Helix at this point.

If there is some magic setting I am missing, do let me know. I have experimented with the bias, bias x, ripple, hum, and sag. This chattering distortion doesn't really change. Right not the bias is at 9.

I have tried a bunch of different amps. Some exhibit this chattering behavior more than others.

Example order - Headrush - Helix - Peavey

 

[waymda]

Sorry, my tin ears only hear:

• something weird with the first part of the "Helix" phrase, it sounds like its been played with a lighter touch
• and the Peavey being louder than both

No chatter that these tin ears can hear.

 

If I put all 3 in a mix there's no way I could tell them apart, perhaps other than the level.

[PierM]

Three different machines, any attempt to make them sounding exactly the same is gonna fail.

 

Said that, the second one (that you said it's Helix), sounds thin and muffled to me like if the guitar signal isn't completely available at the helix preamps, and in the attempt to obtain the same "tube" drive - as the other two devices - you are indeed injecting some unpleasant sparkling and harmonic distortion. You sure you don't have the Pad on?

 

Whatever it is, the first and last sounds much better to my ears, so I'm also curious to know what's happening. :)

[DunedinDragon]

Honestly I couldn't tell all that much difference..at least not enough that I'd spend more than a few minutes adjusting things.  The first one was the most overmodulated,  second was the most consistent and smooth and the third was pretty close to the second but not quite as polished/finished.  But then, I'm not really a dedicated cork sniffer when it comes to tone in isolation.  I do most of my final adjustments in the context of the other instruments I'll be playing with.

 

Just for reference I was listening through my Yamaha HS7 studio monitors and I decided to take some db readings on all three which bore out my initial perceptions.  The first was VERY uneven ranging from maybe 86 to 98 or so, the second was very confined within the range of 85 to 89, and the final one was a pretty similar range until the end when it went into the 90 - 94 range.

[davebode]

On 2/1/2023 at 8:52 AM, PierM said:

Three different machines, any attempt to make them sounding exactly the same is gonna fail.

 

 I wasn't trying to match them. I was trying to evaluate the difference in the distortion from all three. I had been going back and forth from my Headrush to the Helix but I know a lot of folks get hung up on how a modeler might compare to a real amp. So I threw a real amp in there as well.
 

On 2/1/2023 at 8:52 AM, PierM said:

Said that, the second one (that you said it's Helix), sounds thin and muffled to me like if the guitar signal isn't completely available at the helix preamps, and in the attempt to obtain the same "tube" drive - as the other two devices - you are indeed injecting some unpleasant sparkling and harmonic distortion. You sure you don't have the Pad on?

The pad was not engaged on the Helix. It's a fairly strong guitar signal. When I check the input levels on the Headrush my Solar comes it at -6dB if I am smashing chords. I like the Helix a good deal of processing power to run just about anything I'd need to do. But I am not sure I can keep it because this amp distortion is driving me nuts. Once you hear it, you can't unhear it.

Thanks for replying.

[davebode]

On 2/1/2023 at 9:34 AM, DunedinDragon said:

Just for reference I was listening through my Yamaha HS7 studio monitors and I decided to take some db readings on all three which bore out my initial perceptions.  The first was VERY uneven ranging from maybe 86 to 98 or so, the second was very confined within the range of 85 to 89, and the final one was a pretty similar range until the end when it went into the 90 - 94 range.

 

I loudness matched all of the items in Reaper to -17 LUFS and bypassed all my master track effects. I think the uneven quality you are describing is what another might call dynamics. It's odd that you would get readings like that when the first example, the MX5, has the lowest True Peak measurement. That MX5 clip also has the lowest LRA measurement, which is loudness range.

 

Those measurements are in mono. The stereo loudness calculations are exactly 3dB higher.



I appreciate you listening to them and commenting!

 

[somebodyelse]

On 1/31/2023 at 6:31 PM, davebode said:

I just bought a Helix LT as a replacement for my HR MX5. When comparing amp models with the same IR I am noticing that the Helix has this odd behavior on any overdriven/distorted amp. As the notes decay there is a chattering that happens on the upper harmonics. In other words the higher frequency noise doesn't fade away smoothly as the note does. Instead, it kind of chatters like a gate or noise filter when the input is right at the threshold.

I also compared this to a tube amp and tweaked the settings to sound pretty close. Check out the demo. The examples are Headrush AC HI BOOST (Celestion IR), Helix A30 Fawn Brt (Celestion IR), and Peavey Bravo 112 recorded with a Beta57A. I didn't fuss with the positioning of the mic on the Peavey.

 

I would reckon they sound pretty similar. The thing that is bugging me is the distortion decay on the Helix. It comes on and decays rather abruptly and I think I know why. Going back and forth between the Headrush and the Helix and then the Peavey I noticed something. The Headrush and Peavey have a background hiss when the preamp gain is up and the Helix doesn't. Is this some kind of Magic? No.

I think what is happening is that there is some kind of noise filter that is processing the upper harmonics/distortion noise separately from a lower overdriven amp sound on the Helix. As the input envelop starts to decay, it starts increasing the noise reduction/gate threshold and that's why it chatters. It does the same thing on the attacks of notes to some degree. The decay of the upper harmonics/noise on the Peavey  is a little smoother and I don't hear them cut off abruptly like the Helix does. The Headrush also has a smooth decay of the harmonics. To me the Headrush is a bit smoother than this particular Peavey amp, but it's more preferable than the Helix at this point.

If there is some magic setting I am missing, do let me know. I have experimented with the bias, bias x, ripple, hum, and sag. This chattering distortion doesn't really change. Right not the bias is at 9.

I have tried a bunch of different amps. Some exhibit this chattering behavior more than others.

Example order - Headrush - Helix - Peavey

 

 

Haven't listened, because at my age, I probably couldn't hear it anyway.

What you describe sounds like a digital thing where the dsp is 'rounding off' the maths. Used to be a common thing back when we were using gear with lower bitrates. I'd be amazed if you were actually hearing it happen at 48kHz, though.

 

If you've got a noisegate going on, switch it off. Perhaps, try a low pass filter?

[themetallikid]

I havent listened to the clip (yeah, I know....why comment then?) but I havent seen anyone mention the Ripple Parameter.  On some amps this can be quite pronounced with other settings.  

[davebode]

Update - After several hours of manipulating all the amp settings in the Helix I returned it. There was no combination of settings that got rid of that brittle sound of the distortion on the Helix and HX Stomp. I like the Helix and it can produce many excellent sounds, especially fully clipped (high distortion) and clean amp sounds. However the sound of the high frequency distortion cutting in and out, rather than smoothly fading as the note decays, was a deal breaker. Once you hear it, you cannot unhear it. And that stanky distortion sound colors the delays and verbs and it was driving me nuts!

I bought an Fractal Audio FM3 to see how deep the rabbit hole truly goes. The FM3 is brilliant and the sound of the distortion/overdrive/breakup is incredibly good. The way that the distortion/overdrive works is very smooth. If you know someone who has an Axe FX III, FM9, or FM3 go listen to it and poke around with the amps.

No Helix hate here. It's a great unit. The amp models are not for me. The modulation, delays, filters, and verbs are outstanding. I considered keeping the HX Stomp to use as a delay and reverb box with my Headrush MX5. It seemed like too much trouble without the use of a Morningstar MIDI controller and Morningstar has no products to sell. Plus, when I added up the cost of everything (MX5, Cali76 Stacked [because nothing really beats that compressor], HX Stomp, and Morningstar controller) it was more than a FM9. So I returned the FM3 (ate the shipping both ways) and jumped on the waitlist for the FM9.

 

Happy trails Helix Crew!

[soerenP]

So I'm going through the threads here and trying to find out people with similar problems and it seems, there is another one. 

THis is exactly what drives me crazy about the breakup tones I get and in some models it even sounds like a bug. I posted an audio file of the combination Colordrive/HiWatt in another thread and I think some of the crackle just sounds ridiculous. Maybe I need to take the same road @davebode took, but that's kind of a last resort. 

Sorry, it feels like I'm already spamming a bit with this issue. 

[Schmalle]

The Essex A30 is the top boosted AC30 in the Helix.

[davebode]

On 2/23/2023 at 3:12 PM, soerenP said:

So I'm going through the threads here and trying to find out people with similar problems and it seems, there is another one. 

THis is exactly what drives me crazy about the breakup tones I get and in some models it even sounds like a bug. I posted an audio file of the combination Colordrive/HiWatt in another thread and I think some of the crackle just sounds ridiculous. Maybe I need to take the same road @davebode took, but that's kind of a last resort. 

Sorry, it feels like I'm already spamming a bit with this issue. 

I am not sure there is a fix for this. It's not a bug, it's a feature. This is how the Helix amp modeling works. There is some fundamental issue that you and I are hearing that has to do with the way the high frequency noise is attenuated. It sounds ok at full signal, but as the signal decays it cuts off abruptly.

The Helix is still worth a chunk of change. Get rid of it and get on the waitlist for the FM9. Or get a ToneX Pedal and the HX Stomp. Use the ToneX for all the amp and cab stuff and use the HX for delays, mod, EQ, and reverb. MIDI from the HX Stomp to the ToneX for amp switching and add an expression pedal. You will lose XLR out, but that's about the best setup if you want to stay in the Line 6 family.

[soerenP]

Hey @davebode,

 

thanks for the suggestions. I don't think this is a feasible solution for me: Actually I'm a PodGo owner (it's still supposed to use the same models, so landed here), and that for two reasons: 1. Simplicity, 2. Budget. I COULD afford another device like the ToneX pedal, but it's supposed to be an exercise home solution, nothing more professional or complicated.

 

Still, I would like to find out about this distortion issue. I still cannot accept this. I mean, in your example it's clear what you mean, but still quite subtle so some people don't hear it. If you listen to any files I uploaded concerning the Colordrive model, I guess nobody can NOT hear it. It sounds more like an insult to anyone with ears or a bad joke than a state of the art model (I know the Colordrive is legacy, but it's not from the 90ies). 

I will start believing that there's nothing to do about it, when people tell me that they can reproduce it on their devices, but noone else would reply to my comments :( ;) 

 

 

 

On 2/24/2023 at 7:59 PM, davebode said:

that has to do with the way the high frequency noise is attenuated

Hmm. I can't really agree (unless you tell me you've got inside knowledge about how line6 builds their models). Taking the Colordrive examples, it pretty much sounds like there is a sharp knee in the characteristic curve, with a very unsubtle transition from linear to non-linear. I don't think they chop of high frequencies, (which are not "noise" in my opinion, but overtones generated by the distortion). The model rather suddenly stops generating them. My interpretation from what I know about how distortion works. (I'm no modeling pro but still a media engineer, after all.)

Edited February 25, 2023 by soerenP

[z3albw1rr]

On 2/16/2023 at 10:05 AM, davebode said:

 I like the Helix and it can produce many excellent sounds, especially fully clipped (high distortion) and clean amp sounds. However the sound of the high frequency distortion cutting in and out, rather than smoothly fading as the note decays, was a deal breaker. Once you hear it, you cannot unhear it. And that stanky distortion sound colors the delays and verbs and it was driving me nuts!
 

Just wanted you to know, when I listened to your clip, I pressed play without reading it.

 

And I want you to know I know exactly what you're talking about.

 

I heard the first one and I was like, "i don't hear it" and then the 2nd example and I was like "oh yeah, there it is".

 

It wasn't until after that I realized the order - and the Helix was the 2nd one.

 

Yep. It sounded like it.

 

FWIW, this is a common problem in a lot of digital distortion models, not just Line 6. The "fall apart" of the clipping is not smooth as it is in real drive pedals. In fact, I learned this decades ago with the early Fender attempts at modelling - and it was what I actually used to determine if drives were any good or not (all other things being equal). I'd check out the "fall apart" at the end of a moderate drive signal, and if it "cracked apart" then I new it wasn't for me.

 

In the past, Line 6 had enough models to choose from that I could eliminate 90% of them for all the issues they had, and find at least 3 of them that would work.

[codamedia]

Some call this "hair", some call it "squirrels", some call it "grit".

 

When I listed to the examples, the only one that didn't have that was the headrush. Even the tube amp had it.... just less of it. What's unnatural is the Headrush, not the others. Isolate your favorite guitar tracks in recordings, and you will find it will be there to varying degrees. 

 

What is it? It's crossover distortion that occurs naturally in a Class A/B (push/pull) amp. It's part of the power amp modeling. If you don't want that to appear in your Helix.... simply use the "pre-amp" version of the amp instead of the full amp models. (it is more prevalent in some amps than others)

 

[soerenP]

@z3albw1rr, @codamedia

https://youtu.be/wT_w9pL9_w4

Listen closely to the comparisons. Sometimes the real amp got more hair than the Helix!

 

Thanks for the explanation @codamedia. I would dare to say I got it even using pre-amp only, but I'll investigate further! I definitely tend to dial low master values in my patches.