Output distortion solved

[coachz]

I had my output in stomp xl set to +20 and with the cleanest amps it was still very distorted on strums.  I pull it back to 0 and now the distortion is gone.  I'm running into a Digimax FS and have no clipping going in and even pulled it way back to make sure it was not the Digimax FS.  I found 0 is the right level for true clean.  Even +5 on the output has distortion in my unit.  Took me trying lots of amps to realize it was something else.  Anyways,  I hope it helps someone else and I hope Line6 looks into why the outputs have distortion.

[theElevators]

There are so many parameters on the Helix: global settings, preset options, that I recommend starting with a clean slate when things don't make sense....  Rather than figuring out what went wrong, it's faster to recreate the preset from scratch.

 

There's a weird bug for example, that if you copy a block from another preset, the snapshot behavior of that block is completely random and predictable: it's on, it's off, and you can't save its state correctly.  So just delete and recreate it from scratch -- no issues. 

 

That's my approach to life in general, when things don't make sense, start from square 1. 

[coachz]

Yup, that's what I did.  I went back to just the Jazz Rivet 120 & Ventoux with very low drives on them and I still got the distortion with no other fx and the input pad on.  I finally narrowed it down to the Output block and had to go to 0dB until the distortion went away.  Even +5dB had distortion.   It definitely SHOULD NOT be distorting though and I consider this a bug.

[theElevators]

On 10/30/2022 at 1:21 PM, coachz said:

Yup, that's what I did.  I went back to just the Jazz Rivet 120 & Ventoux with very low drives on them and I still got the distortion with no other fx and the input pad on.  I finally narrowed it down to the Output block and had to go to 0dB until the distortion went away.  Even +5dB had distortion.   It definitely SHOULD NOT be distorting though and I consider this a bug.

it's not distortion in the sense of having a boss DS-1... it's just your signal is very very hot and it's clipping...

[coachz]

My signal is NOT clipping the output at 0dB.  As one turns the OUTPUT of the final stage of a device up it should not begin clipping.  Clipping is distortion btw.

[DunedinDragon]

If I were to guess, having your output block that high would most likely cause some level of clipping in the Digital to Analog conversion coming out of the Helix.  I don't know for sure because I've never turned up my output block like that.  Generally I'm reducing my output block to present a more rationally gain staged level to my mixer input.

[MusicLaw]

@coachzWhat firmware version is installed on your Stomp XL?

 

And, why was the Output Block's Level set to other than Zero dB?

 

It never hurts to do a Power On Factory Reset (after first doing a Backup). Then Restore any Customized Presets you may have previously backed up. Then do a Power On Rebuild to be sure everything is converted to the latest Firmware environment. 

[coachz]

Version 3.15 and this is with a new preset with only an amp cab.  It was at +20 because I put it there to test it.  It just seems to be a bug.

[datacommando]

On 10/30/2022 at 3:13 PM, coachz said:

I had my output in stomp xl set to +20 and with the cleanest amps it was still very distorted on strums.

What? 
 

Why?

 

I despair!
 

Truly, I despair!

[coachz]

As an electrical engineer, i test everything so you don't have to.

[PierM]

So, just to recap;

 

you pushed the output to +20dB and were getting signal clipping, so you are letting us know that turning back to 0dB, solved the issue.

 

Output block "level" isnt a last stage volume, it's a boost stage hitting DA, so everything above 0dB is indeed squeezing headroom, and after that there's clipping.

 

The volume you are talking about is the knob on the Helix top/front. That one gives you unity gain when all maxed out, so no boost, no clipping.

 

 

 

[coachz]

So what is the point of having an output that clips the d/a converter. I would have expected the design to have +20DB still have 0 clipping . This is very unusual design.   In what circumstance would anybody push that into a clipping range

[theElevators]

My advice is to use the output block's level as the last resort to level your presets.  Instead of that, simply try cranking the amp, delay level, etc.  Because there's a weird issue where if you switch between presets with different output levels, there's a clicking noise.  Same applies to snapshots if you change that in between snapshots, there'll be an audible pop -- the bigger the discrepancy, the louder the pop.  Same applies to changing your impedance settings between the presets -- same weird glitchy pop.

 

20 db boost is pretty much impractical and unrealistic.  So you can argue whether it's a bug or not, or just accept it as that's how it is.  Helix has a lot of weird quirks and inconsistencies, that you need to just learn to overcome. 

 

From experience, pick your virtual rig, and use the same distortion, amp, etc in all your presets you are planning to use at the same gig, or risk weird noises and other sound guy nightmare scenarios where some presets are way too loud/soft. 

 

Another advice regarding building your preset (courtesy of S. Sterlacci) is to have your actual presets as loud and never louder than a blank preset.  That sounds the most musical, no clipping, no weird digital idiosyncrasies. 

[PierM]

On 10/31/2022 at 2:10 PM, coachz said:

So what is the point of having an output that clips the d/a converter. I would have expected the design to have +20DB still have 0 clipping . This is very unusual design.   In what circumstance would anybody push that into a clipping range

 

That's how dynamic range works, in any audio equipment apparatus.

 

Let's say you have a pedal equipped with 20bit ACs, giving you a good 110dB of dynamic range, with a noise floor sitting at -90dB. Means you have 90dB of range under 0dB (SNR), and 20dB above 0dB (Headroom). That area above 0dB will start clipping as soon as you hit the headroom ceiling (clipping port). Above clipping there is distortion region (transients are all within that area).

 

So, back to helix; that level at the end it's giving you an extra tool to fine tune the gain staging before hitting the DA. If you hit that stage with a good and solid signal (dancing between -18 and +3dB), you are fine, and there is no need to boost that stage over 0dB.

 

It's just a final boost that gives you the opportunity to do little changes on the fly, depending on the situation, without redoing all the gain staging in the preset. Again, 90% of the time, you are good to go with values between 0dB and -/+3dB for adjustments on the fly.

 

There shouldnt be any reason to boost a signal with 20dB, unless you are hitting the output stage at -32/-30dB, which is a very weak and noisy signal (since this is too close to noise floor, and boosting will pull that noise up.)

 

You do your gain staging BEFORE to hit the output block, trying to stay in the headroom zone, or just a tad under it. If you do so, that output level should be fine at zero.

 

 

[coachz]

Thank you for the detailed explanation. That's very helpful

[HonestOpinion]

On 10/30/2022 at 11:13 AM, coachz said:

... Even +5 on the output has distortion in my unit.  Took me trying lots of amps to realize it was something else.  Anyways,  ...

 

 

Although +20db is a fairly radical boost, @coachzalso reported getting distortion at +5db on the output. That generally should not be happening. Many users have a several db boost on the output block because they either want a completely "clean" boost, or maybe because they need to save a block and so don't want to use a gain block. I mention it because perhaps @coachz has surfaced an issue where a "hot" preset causes a raised output block setting to have a more adverse impact than one might anticipate. In which case, good to know. Again, at +20db, all bets are off, but at +5db they shouldn't be unless the signal level in the preset is already too high before hitting the output block per @PierM's headroom calculations.

 

Your signal clipping already further up in the signal chain as @PierMalluded to and the output block just making it more obvious, does seem like a viable theory. Does this still occur when you run a preset that has an intentionally low signal level before the output block? Btw, how were you determining that your signal was clipping after output? Your ears (clearly audible), some other method such as visible in a DAW? Does it clip via headphones directly from the Helix?

[coachz]

This is great information. I was using just an amp cablock like a jazz 120 rivet or a ventoux but I was pushing the level up quite a bit. I think you're right that I need to make sure that I don't have clipping up to about 10DB so I have some room for adjustment down the road.. Also I was using my ears and it was clearly audible. Great stuff and  very appreciated thanks.   The stomp xl is freaking unreal. The sounds I'm getting out of this thing are absolutely incredible

[gbamburg]

I for one (new Helix user) am thankful for this thread.  I was up all night last night dealing with distortion/clipping issues thinking i have a defective unit.  Armed with this info i have high hopes for tonight.  

[MusicLaw]

@coachz There is an excellent book entitled: The Big Book of Helix Tips and Tricks authored by Craig Anderton available as a PDF from Sweetwater Publishing. It has plenty of information about constructing Presets and Gain Staging, plus over 100 sample Presets. Check it out! Many have found it helpful to improve their use of the Helix family of products.

[coachz]

I'll go read the gain staging sections right now.  Thanks !!!

[coachz]

I read the Gain Staging section of the The Big Book of Helix Tips and Tricks but it didn't get me where I wanted to be. 

 

My Stomp XL is set Globals / Input Gain / Instrument (intentionally for more headroom) and the presets have Global Guitar Pad set to Global.

 

From there I needed to find a way to indicate where output clipping is since there is not a meter.  I thought I could use the Green/Red output light on the Stomp XL display but I found that I can push the outputs into clipping and the output clipping indicator is still green (BUG ?). 

 

Using my ears I loaded the clean Jazz Rivet 120 and just strummed a D chord hard on the guitar and started pushing the output level of it and the Main L/R output until I clearly heard clipping of my clean hard strums.  I found that it didn't matter if I pushed up the Rivet amp level or the Main L/R levels, the dB increases have the same effect as expected.

 

I'm running the outputs into a Digimax FS and into an RME9652 into Reaper on a new Tuf Gaming X670E Plus Wifi with a 7950x cpu and 64gb ram woot.....

 

After finding the clipping point and adjusting levels down about 5dB to give some headroom I was able to adjust my Digimax input levels to provide -6dB on my meters in Reaper on the hard strums.  If I keep this level coming out of the Stomp XL then I will have enough headroom to avoid clipping.  Just wanted to share because you can never get the sound you want if you have unintended clipping.  So I saved this as a preset in case I need to get back to checking these levels again.   I hope it helps.

 

 

 

[datacommando]

On 11/4/2022 at 2:46 PM, coachz said:

I'm running the outputs into a Digimax FS and into an RME9652 into Reaper on a new Tuf Gaming X670E Plus Wifi with a 7950x cpu and 64gb ram woot.....

 

Hi,

 

This may sound obvious but have you tried taking the DigiMax FS preamp out of the equation, and use the USB audio out of your Helix directly into Reaper using a USB port on the computer? Now, I'll bet that you're going to tell me that your RME (Hammerfall?) 9652 doesn't have USB. I guess you are taking ADAT Optical out of the preamp into the sound card ADAT Optical in

 

I only want to ascertain if you can, or cannot, get a clean (non clipped) signal out of the HX Stomp XL and into the DAW. I have an awful nagging feeling that somehow you are overdriving the inputs of the PreSonus - although I realise that you keep telling us that is not the case.

 

The reason I mention this is because the Owner's Manual for the DigiMax FS does state:

2.3 Instrument Input

"Care should be taken not to overdrive these inputs with the signals from instruments with on-board preamplifiers.

I would think that your HX Stomp counts as having on-board preamplifiers.

 

Also from the Tech Spec sheet.

Maximum Input Level (Unity Gain, 1KHz @ 0.5% THD+N)  +11dBu

 

If you say that having nothing but a clean Jazz Rivet 120 in the preset is causing this - then this is the only thing that makes sense to me. I just added a clean Jazz Rivet 120 (yes a Legacy amp/cab block) to a path with nothing else, then that goes out it Logic on the Mac over USB. Result - no clipping, no distortion, simply a clean JC tone. Go figure.

 

Hope this helps/makes sense.

[zappazapper]

Why is the setting on the output volume relevant in terms of clipping? If there's clipping, there's clipping, regardless of what the setting is. If it's set to -60 and there's clipping, there's clipping. If it's set to +20 and there's no clipping, there's no clipping. Almost every effect on the Helix is a model of a hardware unit, many of which don't output at unity when supposedly set to unity, so an output volume is essential, and while a setting of +20 means you probably could use better settings somewhere earlier in the signal chain, it's better to have more gain available and not need it than needing more gain and not having it. 

[coachz]

I have been using the RME9652 and Digimax for over 10 years and am very comfortable at setting levels.  In fact the clipping on it corresponds exactly with the 0dB meter on my Reaper tracks.  The Digimax will even flash red before I can even hear any clipping.  I don't use the USB because it doesn't work with the RME9652.  

 

With just the Jazz Rivet 120 I have the level at +10 and still have headroom before clipping so that sets a great reference for me.  I also have Input set to Instrument so that gives me more headroom on the input stage.

 

When I add another 5dB I get clipping whether it's from a Volume block or the Output level.  ATM this is doing exactly what I need and providing me a reference for the output of the Stomp XL.  If it had an output meter like a mixer or if the output green light would turn red like it is supposed to  I would easily be able to tell if it was clipping visually.

 

The reason the output volume is relevant is it lets me have a reference for the output stage as to what level it begins clipping and there is no longer any headroom.  I'm sure there are other ways but since the green light on the Main out isn't going red for me when I hear audible clipping this is what I came up with.  So ....everything is working great here and I just shared this in hopes other could benefit from it.  Rock on !!!

[zappazapper]

On 11/4/2022 at 3:49 PM, coachz said:

...the green light on the Main out isn't going red for me when I hear audible clipping this is what I came up with.

Fair enough. It begs asking what exactly triggers the block going red. Is it a peak meter or RMS (maybe someone with accurate info can chime in)? Signal peaks going past full-scale digital doesn't necessarily manifest itself as audible clipping. I'll second the suggestion to take as much gear out of the equation to see if that changes anything. What you hear might not be the output of the Helix clipping; it might be the input of your interface clipping. AFAIK a DAC isn't simply a ADC wired in reverse, not to mention that even if it was, it's unlikely that both devices have the same brand and model of chip. Different devices behave differently. My recording rig is two MOTU firewire interfaces with 3 Behringer ADA8200s connected via ADAT Lightpipe, and I can say with confidence that audible input distortion happens at different levels on the MOTU gear than the Behringer stuff. And I'm not even sure if that has anything to do with the converters most likely being different brands and models. The preamps themselves are different, as are the anti-aliasing filters. Any of these things could affect what you hear, and taking everything out of the equation besides your guitar, your Helix, and your speakers/headphones is going to tell you more about clipping in the Helix output than the way you are currently connected. 

[coachz]

As suggested I went back and used the direct Stomp XL USB interface into Reaper.  The results were the same.   With my Jazz Rivet 120 at level +10 and Master out at 0, everything is clean.  At +5 Master out level I get clipping in my daw and at +2dB I do not and of course at 0dB I do not.  Also, the light on the output stayed green the whole time and never went red....disappointing.   I hope it helps.    This gives me a very solid level to know when I'll clip the output of the Stomp XL.   

[zappazapper]

On 11/4/2022 at 4:59 PM, coachz said:

As suggested I went back and used the direct Stomp XL USB interface into Reaper.  The results were the same.   With my Jazz Rivet 120 at level +10 and Master out at 0, everything is clean.  At +5 Master out level I get clipping in my daw and at +2dB I do not and of course at 0dB I do not.  Also, the light on the output stayed green the whole time and never went red....disappointing.   I hope it helps.    This gives me a very solid level to know when I'll clip the output of the Stomp XL.   

That leads me to belive that the clip indicators are based on RMS and not peak level. At any point in your test did you hear audible distortion? Because if you didn't, it might be interesting to see whether the clip indicator goes red at around the same level it takes to create audible distortion. Like I said, peak clipping past full-scale digital is not necessarily a bad thing if you don't hear distortion. 

[coachz]

yeah it's very audible distortion at my +5 level on Master out when Rivet is at level +10

[zappazapper]

Would you mind sharing your preset so I can test it myself tonight when I get a chance? 

[coachz]

here.... thanks

-6dB hrd stm Rpr.hlx

[zappazapper]

On 11/4/2022 at 5:13 PM, coachz said:

here.... thanks

-6dB hrd stm Rpr.hlx 3.81 kB · 0 downloads

OK so I tested it on my LT and I'm not getting the same behavior as you are. 

 

The first thing I'll point out is that I had to change the output block from "Multi Output" to "USB 1/2". "Multi Output" sends the signal to the 1/4" jacks, the XLR jacks, the Digital Out (not on your XL), and the USB 1/2 channel, which appears in Reaper as Input 1 and Input 2. The Phones jack by default mirrors the Multi-Output, as well as what is fed into Output 1 and Output 2 in Reaper. In that case you would be hearing both the internal signal in the Helix, AND the signal being fed into Reaper and back to the Helix, which would be 6 dB louder. I'm assuming that you are aware of this, set the output properly to USB 1/2 when doing your Reaper test, and that the preset you sent me was the original preset that you were using when you had your Stomp plugged into your interface.

 

Anyway...

 

I did not get audible distortion with the output volume set to 0.

I did not get audible distortion with the output volume set to +5.

I did not get audible distortion with the output volume set to +10.

I DID get audible distortion with the output volume set to +20, and the distortion was 100% correlated to the output block turning red to indicate clipping. 

 

There's an almost 100% possibility that the output circuitry in the Stomp is different than the output circuitry in the LT, although it would surprise me if L6 didn't optimize the clip indicators in the Stomp to turn red when it's own specific circuitry clipped.

 

I still maintain that there is some aspect of your setup that is adding gain and causing you to hear audible distortion that the unit is not causing itself.