Volume drop connecting Helix to PC Plus via L6 Link

[soundmodeler]

 

I recently bought a Powercab 112 Plus, which I use with a Helix. Although for a while I was using an XLR cable to connect the two, I decided to buy a Line 6 Link cable as a substitute, mainly so that the Helix could control the Powercab without using Midi – something that I realize can’t be done right now, but which might be possible down the road.

 

Unfortunately, when I connect the L6 Link to the Powercab, there’s an approx 30% volume drop compared to the XLR cable. I connect the L6 Link from the Helix “Out” to the Powercab “In,” as I’ve read that I should, so I don’t think I’m using the wrong outlets/ports.  Both cables are 20 feet long, so the volume drop can’t be due to distance changes. I’ve turned off/on both the Helix and the Powercab and reconnected them a few times to see if that made a difference, but nothing. The L6 Link could be defective, but I can’t see any obvious signs of physical damage.  

 

The sound quality is unaffected - no pops, hum, hisses, or intermittent connection.

 

Any suggestions about what the problem might be? Thanks.

[gtr1]

I did the same thing a few months ago, I was using XLR and bought the L6 link cable for my powercab plus just to be ready for Midi in the future and I CAN confirm the same results. The sound quality is not effected but the volume did drop off quite a bit. I have switched back to Xlr. I hope they will fix this in a firmware update.

[soundmodeler]

Thanks for chiming in, gtr1. Just after I posted here, I decided to send Line 6 a support ticket about the issue. They responded with some advice that helped a little, but didn't really solve the problem. It turned out that I wasn't using the "digital out" from the Helix output block to the Powercab, which meant that I couldn't adjust the "level" parameter to raise the signal. When I did this, as Line 6 suggested, I got an increase in volume, but even at maximum level it still wasn't nearly as high as when using XLR. So I'm switching back, like you did. 

[SteveFrance]

I had the opposite.

I had a lower volume with XLR than L6 link.

The reason is that there's a volume parameter that you can setup on the XLR input, you can't on L6 link.

To be concrete, my input 1 was at -18db, so when i was plugging on the L6 link, it was louder.....

I think your input 1 & 2 are set to 0dB (default), so when you go on the L6 link the volume drops.

You should tweak this parameter to be equal between inputs (press the house icon). 

And you have to increase the volume db per speaker (when you press the big knob on the model speaker you use).

 

[soundmodeler]

SteveFrance, thanks for your comments, although I'm not sure that I follow you. Both XLR and L6 Link (digital) outputs have a volume/level parameter, as far as I can see. I've boosted both to 20db and the XLR is louder.

 

I'd be grateful if you would say what you mean by adjusting my Inputs 1 and 2. I'm only using 1 input (set to Multi), where the Helix receives my guitar signal, so I don't yet see why making adjustments there (Input Gate/Guitar In-Z) would influence the volume coming out of the Powercab. 

 

Are you talking about channels 1 and 2 on the Powercab itself?

[soundmodeler]

SteveFrance, I now understand what you're talking about. I didn't realize that there's a global 2-channel XLR gain parameter in the Powercab 112+. I thought you were talking about the Helix outputs, XLR or digital (L6 Link), both of which have gain parameters. Thanks for shedding light on how the Powercab can be tweaked, including that fact that each speaker model has a volume level adjustment of up to 6 dB.

 

Like you said, the Powercab inputs are factory-set rather low,  0dB or lower. Naturally, since yours was at -18db, your XLR cable connection was NOT as loud as the L6 link. So you increased the XLR input gain until the volume from that cable equaled the volume you were getting from the the L6 Link. Makes sense. 

 

Maybe you noticed this too. If you increase both Input Gains - and especially Input 1 - to 12 dB (their maximum), the XLR volume greatly exceeds that of the L6 Link. At least, that's what happens when the Powercab is connected to a Helix. So why use L6 Link with a Helix? I'm getting less bang out of the L6 Link in terms of volume and it doesn't offer any other functionalities, like control of Helix presets, etc. This is a "lose, no-win" proposition, especially for a $60 dollar cable (the medium-length L6 Link). 

 

 

 

 

[SteveFrance]

This is  little bit tricky to explain things by posts (and if you don't know exactly where to go in device's menus) but you've understood what i wanted to tell ;).

 

On the PC+, there are three ways to pump up the volume with XLR (the big knob, of course, the db level per input and the db level per cab model) and only 2 with L6 link. The only add for the L6 link today is that it can split automatically the signal into two path for stereo if you have another PC+. I hope that tomorrow, it will possible to change the cab model with that cable. For the definition, it would be better but i don't find a big difference between them.

 

 

[soundmodeler]

Okay, thanks for pointing this out. Since I don't plan to get another PC+ anytime soon, the L6 Link won't help me there. But I see the convenience for stereo users. 

[somebodyelse]

Okidoki, I'm still pondering taking the plunge in to Helix/PowerCab+ world, BUT...

 

The point of the L6 link is that being a digital link, it saves the Helix and PC+ from having to convert the signal from digital to audio and back again 'in between units'. This saves processing power in both units, keeping latency low.

The other, better reason for linking the two 'units' digitally is 'that harshness' that a lot of people complain about in digital processing and recording is usually the result of 'inter-modulation distortion' caused by AD and DA converters - a good reason to use the high cut filter on the PC+.

Whilst I'm aware of how and what causes this distortion, I'm afraid if I try to explain it, I'll get it wrong somewhere along the line. There are plenty of explanations out there, suffice to say, the less to-ing and fro-ing between digital and audio the better.

 

EDIT: Of course, everywhere I've said "digital to audio", I should have said 'digital to analogue' - it'e pnly audio after it leaves the speaker.

[PaulWilliamson]

 I have the same issue, using the L6 Link connection there is a considerable volume drop to my Powercab+

 

It just seams odd that using the supposedly optimum connection method, there is such a drop in volume. 

 

I too want the ability (when the next update arrives) to control the Powercab+ speaker models through the L6 Link.

 

But why should it mean having to run the Powercab+ at a much higher volume setting to get the same output as either Line or XLR.

 

A factor that makes this slight issue worse, is the inability to alter the L6 Link output independently from the Helix.

 

I appreciate that the Line 6 Link reduces digital to analog conversion, but the lower output negates any benefit from this.

 

I'm hoping it's an oversight that can be rectified, because I have gone back to using an analog XLR connection. 

 

To me it sounds fuller and more convincing than the slightly feeble digital L6 Link output signal I was getting.

[soundmodeler]

PaulWilliamson - totally agree with your assessment. My issues exactly!

[PierM]

On 4/16/2019 at 9:13 PM, PaulWilliamson said:

A factor that makes this slight issue worse, is the inability to alter the L6 Link output independently from the Helix.I

 

You could raise the Level acting on the output block

 

 

[soundmodeler]

Thanks PierM

[PaulWilliamson]

Thanks, I appreciate your advice, but unless I'm missing something, that is sort of a work around rather than a fix. It means editing each preset individualy. 

 

I would have thought the digital output using L6 Link at any given setting should be gain matched to the other outputs. Line, XLR analog at say zero dB should be the same volume as L6 Link at zero. 

 

I know its not a major issue, but its just puzzling and I wonder if its by design or just some anomaly of the firmware.

[somebodyelse]

On 4/19/2019 at 6:08 PM, PaulWilliamson said:

...I know its not a major issue, but its just puzzling and I wonder if its by design or just some anomaly of the firmware.

 

No, it's not an anomaly.

The difference between a digital signal and an analogue signal is like the difference between sending an email and making a phone call.

 

 

[yrebrac]

On 4/21/2019 at 6:18 PM, somebodyelse said:

 

No, it's not an anomaly.

The difference between a digital signal and an analogue signal is like the difference between sending an email and making a phone call.

 

 

 

I fully agree with this, however I think there is a good point buried in the post.

 

In helix we have a multi-output block that ties the output of the modeller to a single volume control knob, and then ties the output of the volume knob to the output jacks.

 

The AES output jack simply takes the digital signal from the output of the volume knob and sends it. This signal has already been transposed by the volume knob (i.e. all 24-bit numbers adjusted up or down by the same amount).

 

The XLR output takes the same digital signal but has to convert it to an analogue signal prior to sending it. There is no fixed way to convert the digital signals volume, however - it can be mapped to anything that conforms to the standard for that analogue signal. There's a lot of wiggle room there (but even at this point, there is no inherent "volume" in the signal. Both the analogue and the digital signal are only encoding differences in volume).

 

So we now send both a digital and a converted analogue signal to the same device - a powercab in this example. The powercab does the reverse operation on the XLR signal and converts it to digital. Again it has a choice about how 'loud' it interprets the XLR signal in digital terms. It then does it's modelling thing and the modified signal is sent to the speaker for another round of analogue conversion in the form of moving a speaker. For the digital input it does nothing before modelling (assuming no input gain change), no conversion required.

When the signal hits the speaker is the first time there's an inherent volume to the signal. Prior to this we were only encoding differences in volume.
 

Now, all things being equal - all the volume settings on the helix, and all volume settings on the powercab - we SHOULD get roughly the same volume at the speaker whether we use the AES output or the XLR output on the Helix. Not for a technical reason but for a practical reason. But we don't.

 

It doesn't make sense to have different signal transport methods produce wildly different results with all other things being equal. I agree with OP to an extent - I wouldn't expect the volumes to be totally matched but I wouldn't expect them to be totally different either (say by more than 6dB).

 

So is this the fault of the helix or the powercab? It could be either, it's not possible to say as there are two places the signal is being converted where there's a somewhat arbitrary decision about how to translate a signal's volume from one form to another - before it's sent by the Helix and after it's received by the Powercab.

 

But certainly it's fixable in the firmware of either.

 

It's also totally fixable by the user. By adjusting the 'Digital Output Level' setting up or down to match to the level of Helix-XLR + Powercab-XLR conversion. Unlike all other volume controls, this setting will ONLY affect the AES output. I think this is the wrong way of thinking about however, I view this setting more as on offset for the XLR output, where there is some interpretation of volume going on.

 

In short, I agree with OP that there's a questionable aspect of the implementation, but not that it needs to be fixed by Line 6. You figure out the difference once, you adjust the setting, then you forget about it. Now you can switch between digital and analogue outputs to your heart's content.

 

 

 

[SteveFrance]

Your powercab is badly adjusted.

You can/should have exactly the same level between the XLR and the L6 link.

 

The method would be this one :

- Helix out on multi - Volume knob on the position you have the habit to use.

- link the Hx and the PC+ with L6 link

- Play a preset and remember the dB level

- Plug all in the XLR/Jack input and go in the main menu (house icon) on the Input 1/2 gain, decrease the value to obtain the same (low) volume as the L6 link (you can setup the input 2 lower if you want to play at home for example)

- Select each model/FRFR speaker while turning the LED knob, press it and increase all the dB parameters. You can do so with a same preset (except for the FRFR) to have the same volume between speaker models (I know i have many dB of difference between the jarvis and the greenback). Increase it and play to see if the light don't blink in red. If that's the case decrease a little to prevent it.

 

Play with the Helix/PC+ volume knob to obtain what you want following the conditions....

Enjoy !!!

 

[amsdenj]

Turning the patch output up or the PC+ XLR input down certainly can be used to achieve similar levels between the XLR and AES outputs. But it would be convenient if Line6 normalized these so the typical 0dB settings on Helix output and PC+ XLR input were the same. This would simplify patch management when using different FRFRs.

 

I also find the AES PC+ input volume a little low. I have to run the PC+ and Helix output knobs up pretty high to get sufficient stage volume. Its enough, and there’s plenty to spare, but it just seems the knobs have to be up pretty high.

[yrebrac]

On 5/9/2019 at 7:04 PM, SteveFrance said:

Your powercab is badly adjusted. 

 

 

 

But see my post above and show that it's not the helix that is badly adjusted - there's two points where a digital is converted to analgoue of vice versa. Someone with another digital cab would need to compare to be sure.

[SteveFrance]

Well, i had another look at  the PC+ to see all the setups i've done and retried the different input. 

I've changed between the L6 link and the input 1 and didn't notice any volume difference.

Here are my setups (only on the powercab, the idea is to have the same volume whatever the link you use) ;

_Input1 Gain : 0dB

-Input2 Gain: -10dB (to play lower quickly if i wanted to) I don't use those two inputs now but only the l6link

-Flatlevel : 3dB

- Vintage : -9,5dB

- Green : -9,5dB

- Cream : -10,5dB

- Jarvis : -7,5dB

- Bayou : -10,5dB

- Essex : -8,5dB

- Natural : -9,5dB

I've done this setup if i want to change the speaker model, then, they have the same volume.

 

The last thing, that wouldn't have any incidence on the sound but i've found it had, i've defined a mic/position/high & low cut for all model speakers : the high and low cuts are at 65/70Hz and 13KHz. The mic is the 160 or 121 Ribbon at 2" or 3" distance.

 

 

 

[yrebrac]

I agree it's roughly 10dB difference between the models and the Flat modes, but it will depend on the amp as well. I have to adjust slightly for different helix presets

[SteveFrance]

In flat mode, i use an acoustic guitar or i add a cab modeling that drops the volume, this is the reason why, in this mode, i need more volume.

In speaker model, i've tried to go to 0dB for many of them to increase my volume but the red light appears in continue, i would say those values per speakers are the limit with amps parameters by default. If you turn up, the gain, the volume and the master it generates digital clipping too.

[feffa86]

On 5/25/2019 at 12:13 PM, SteveFrance said:

The last thing, that wouldn't have any incidence on the sound but i've found it had, i've defined a mic/position/high & low cut for all model speakers : the high and low cuts are at 65/70Hz and 13KHz. The mic is the 160 or 121 Ribbon at 2" or 3" distance.

 

 

 

That only affects the XLR output on the Powercabs, not the sound in the speaker. If it does for you, I don't know the explanation, but the conceptual idea is: when you play through the Powercab with speaker models used, it is supposed to sound like an actual amp or cabinet in the room. So no mic or preamp in the signal. But if you want to record that sound, instead of using a regular mic and a mic preamp, which is the go-to solution the powercab simulates those on the XLR output. It's part of the "amp in the room, all in one stage rig" thing they're going for. Helix straight into PC+ is all you need. That is how it is intended and advertised to work.

 

As for your question about levels, I just figured I'd chime in. You may all be right, or wrong for that matter, I don't know, but I haven't seen anyone talk about why there is a volume difference. Bear with me here, but so if you imagine the internal sound signal inside the Helix, one can easily imagine that internally, it is at its "natural" volume level. When that signal is fed into an output, different outputs have different properties. 1/4" unbalanced line level is louder than XLR balanced line level.  Don't mistake that though, if you have an amp with an unbalanced 1/4" & a balanced XLR output, and an active speaker with an unbalanced 1/4" input and a balanced XLR input, so long as you go from balanced to balanced and unbalanced to unbalanced, there is no difference in volume. But if you feed a balanced XLR output into an unbalanced 1/4" input, the unbalanced input will likely clip. It will be louder "than intended" or however I should put it. You will be above unity gain. You could say if you were landing a rocket, you're way out to sea. That  is another thing no one mentioned. Unity gain. For the inputs and outputs to be matched and for the units to be gain staged so that there is no artificial boosting of the volume to get you were you want to be. You don't want that. It's not a matter of taste, it's a matter of what is correct and what is wrong. If you (not just OP, anyone reading) care about tone but don't know about unity gain, you should wrap your head around that before you do anything else. Especially if you got a complex rig.

 

So when you use digital, with the volume control at 100%, you are sending the full signal that is inside the Helix to the outputs. If that's lower than before, that suggests to me that before, you were actually feeding it a signal that was "too loud". You were possibly slightly overloading the Powercab input. Considering it's not an amp, but an FRFR speaker, I can only imagine that that distorted your signal (but possibly so little that you wouldn't notice it unless you did actual A/B tests with recorded clips in headphones). I could be wrong, but it sounds like your volume isn't too low now, it was too high before. What you are now getting is the entire internal signal, with its headroom. Maybe what is actually the case is, because you were feeding the Powercab a signal that was too loud for the input, you've dialed in your patches accordingly. Now that you are at unity gain, maybe you can increase the channel volume on the amp without clipping, where you would earlier clip. You should look into that. Or connect an XLR into the PC output and record to your computer. If your signal is peaking, then I'm wrong, but I'm pretty sure if you do that, you'll have loads of headroom to go on. That's not a bad thing btw, but if things aren't as loud as you want (percieved loudness) that also means there's something you can do about it. I'm curious though, are you actually unable to get the PC to be as loud as you want when you turn it all the way up, or was it more the difference from before that was bugging you, leading you to think something wasn't right?

 

In my rig I have two Powercabs. I run a Kemper in an FX loop on the Helix and some pedals in the other loops. There's a lot of cables and I've gain staged every unit. I run my computer sound through the Helix so when I watch Youtube videos on evenings I have my PCs' volume controls set to 30% and I still have to lower the Windows volume to between 12-20% so as to not keep my neighbours up. What I mean to say is, that volume is louder than regular living room TV volume, at 15% of 30% (so what, 4,5% of max volume). I am physically afraid to go past 50% because when I get close I can feel my ears start to hurt. Like, gunshot loud hurt.

[SteveFrance]

On 5/31/2019 at 11:53 PM, feffa86 said:

That only affects the XLR output on the Powercabs, not the sound in the speaker. If it does for you, I don't know the explanation, but the conceptual idea is: when you play through the Powercab with speaker models used, it is supposed to sound like an actual amp or cabinet in the room. So no mic or preamp in the signal. But if you want to record that sound, instead of using a regular mic and a mic preamp, which is the go-to solution the powercab simulates those on the XLR output. It's part of the "amp in the room, all in one stage rig" thing they're going for. Helix straight into PC+ is all you need. That is how it is intended and advertised to work.

 

As for your question about levels, I just figured I'd chime in. You may all be right, or wrong for that matter, I don't know, but I haven't seen anyone talk about why there is a volume difference. Bear with me here, but so if you imagine the internal sound signal inside the Helix, one can easily imagine that internally, it is at its "natural" volume level. When that signal is fed into an output, different outputs have different properties. 1/4" unbalanced line level is louder than XLR balanced line level.  Don't mistake that though, if you have an amp with an unbalanced 1/4" & a balanced XLR output, and an active speaker with an unbalanced 1/4" input and a balanced XLR input, so long as you go from balanced to balanced and unbalanced to unbalanced, there is no difference in volume. But if you feed a balanced XLR output into an unbalanced 1/4" input, the unbalanced input will likely clip. It will be louder "than intended" or however I should put it. You will be above unity gain. You could say if you were landing a rocket, you're way out to sea. That  is another thing no one mentioned. Unity gain. For the inputs and outputs to be matched and for the units to be gain staged so that there is no artificial boosting of the volume to get you were you want to be. You don't want that. It's not a matter of taste, it's a matter of what is correct and what is wrong. If you (not just OP, anyone reading) care about tone but don't know about unity gain, you should wrap your head around that before you do anything else. Especially if you got a complex rig.

 

I know how it WOULD work and i was estonished too. In fact, i've read that on a thread on "the gear page" website....After trying that at home, i really noticed a difference with and without those setups....

 

For the connection, the OP had a problem between XLR/1/4" input and L6 link. The only way to equalize those inputs is to play on the input gain parameter, you can tweak it between 

–95.5~+12.0dB, i think it's enough to find the same loudness....

[heashon2000]

I just bought the Powercab 112 plus and am reading through this information. It sounds like the only reason to buy the L6 link (for the time being) is to eliminate processing (and possibly noise?) for recording.

 

Without buying another 112 plus, I would say it is probably not worth the $60 cable for now.

[phil_m]

2 hours ago, heashon2000 said:

I just bought the Powercab 112 plus and am reading through this information. It sounds like the only reason to buy the L6 link (for the time being) is to eliminate processing (and possibly noise?) for recording.

 

Without buying another 112 plus, I would say it is probably not worth the $60 cable for now.

 

The latest Helix firmware update allows you to control everything in the Powercab remotely via L6 Link now. It’s well worth the cost of a cable. You don’t have to buy the Line 6 version. Any AES/EBU cable will work.

[HonestOpinion]

On 8/9/2019 at 7:10 PM, phil_m said:

 

The latest Helix firmware update allows you to control everything in the Powercab remotely via L6 Link now. It’s well worth the cost of a cable. You don’t have to buy the Line 6 version. Any AES/EBU cable will work.

 

And while you're waiting for your AES/EBU cable to arrive you can probably use any decent XLR cable. Best not to use a long one.

[HonestOpinion]

On 12/4/2018 at 9:09 AM, soundmodeler said:

 

I recently bought a Powercab 112 Plus, which I use with a Helix. Although for a while I was using an XLR cable to connect the two, I decided to buy a Line 6 Link cable as a substitute, mainly so that the Helix could control the Powercab without using Midi – something that I realize can’t be done right now, but which might be possible down the road.

 

Unfortunately, when I connect the L6 Link to the Powercab, there’s an approx 30% volume drop compared to the XLR cable. I connect the L6 Link from the Helix “Out” to the Powercab “In,” as I’ve read that I should, so I don’t think I’m using the wrong outlets/ports.  Both cables are 20 feet long, so the volume drop can’t be due to distance changes. I’ve turned off/on both the Helix and the Powercab and reconnected them a few times to see if that made a difference, but nothing. The L6 Link could be defective, but I can’t see any obvious signs of physical damage.  

 

The sound quality is unaffected - no pops, hum, hisses, or intermittent connection.

 

Any suggestions about what the problem might be? Thanks.

 

 

On 5/9/2019 at 2:52 AM, yrebrac said:

 

...

It's also totally fixable by the user. By adjusting the 'Digital Output Level' setting up or down to match to the level of Helix-XLR + Powercab-XLR conversion. Unlike all other volume controls, this setting will ONLY affect the AES output. I think this is the wrong way of thinking about however, I view this setting more as on offset for the XLR output, where there is some interpretation of volume going on.

 

In short, I agree with OP that there's a questionable aspect of the implementation, but not that it needs to be fixed by Line 6. You figure out the difference once, you adjust the setting, then you forget about it. Now you can switch between digital and analogue outputs to your heart's content.

 

 

 

 

Seems like yrebrac's suggestion is the way to go. Has someone discovered a better method? Still waiting for my PC+ to arrive. From what I have read here so far it seems like adjusting Global Settings > Ins/Outs > 'Digital Out Level' (I am assuming this was the parameter yrebrac was referring to) would be the way to deal with the volume differences as it is a global option so it does not require a separate adjustment in every preset. As he stated, set it once and forget it.  I know this global setting can control the AES/EBU level so I am assuming it is also able to control the L6 Link output level? Does it? Can't test this myself until it arrives.

 

Also agree with yrebrac's last point which is that all other things being equal and set equivalently, ideally the digital, XLR, and 1/4 outputs should have output levels in the same ballpark but as long as raising the 'Digital Out Level' doesn't degrade the sound in any way the volume disparity seems easy to work around.

[HonestOpinion]

Now that I have a PC+ and can test it, It appears that on the Helix the Global Settings > Ins/Outs > 'Digital Out Level' does not control the level out via L6 Link to the PowerCab+. It has no effect on the PC+'s volume. Is everyone else seeing the same thing? Maybe it works with AES/EBU but not with L6 Link. At least not for me. Is this as designed or is this a bug in the Helix 2.82 firmware? I'm on PC+ firmware 2.00.1.

[yrebrac]

Hmm, are you sure L6 link is even a different cable? I thought it was just referring to the line protocol being slightly modified. Pretty sure I'm just using an AES cable, controls everything perfectly, but digital out still works. I'd have to doublecheck on the current firmware though.

[HonestOpinion]

1 hour ago, yrebrac said:

Hmm, are you sure L6 link is even a different cable? I thought it was just referring to the line protocol being slightly modified. Pretty sure I'm just using an AES cable, controls everything perfectly, but digital out still works. I'd have to doublecheck on the current firmware though.

 

Thanks for checking this out. I think I see the confusion. I was trying to say that perhaps the Helix's Global Settings > Ins/Outs > 'Digital Out Level'  might work properly if you had the AES/EBU connection going out to some other device but does not seem to work when connected via "L6 Link" to the PC+.

 

The L6 Link cable is just a standard AES/EBU cable. I am using an AES/EBU cable. My understanding is that L6 Link is some kind of Line6 proprietary customized variation of the AES/EBU protocol. So the protocols may differ(?) but both use the same type of cable. Are you saying that the Helix's Global Settings > Ins/Outs > 'Digital Out Level' is able to raise and lower the volume on your PC+?  It is definitely not working on mine. I'm talking about using the Helix's global setting and not the level that is available from the preset.

[HonestOpinion]

Think I figured out what is going on. The Global Settings > Ins/Outs > 'Digital Out Level'  does not work with L6 Link (neither does the 'Sample Rate') and at least for now this appears to be by design. They imply it in the Helix manual by saying it is not "necessary" without spelling it out explicitly. The manual also doesn't mention the PC+ 'cos that device hadn't been released to the public yet when the Helix manual was written. The Global Settings > Ins/Outs > 'Digital Out Level'  setting will probably work with other AES/EBU connected devices. Haven't had a need for AES/EBU myself so haven't tested it, but I can confirm it doesn't work with L6 Link. At least for me and as per the manual.

 

From the Helix Rev.D manual pg. 22:

L6 LINK Output

Alternatively, the digital XLR connector can be used for L6 LINK output (use of a 110Ω XLR cable is recommended). L6 LINK provides easy digital audio connectivity between Helix and Line 6 StageSource speakers and/or DT-Seriesamplifiers. Two StageSource speakers or DT amps can also be connected in series via L6 LINK and your stereo Helix signalis intelligently split,with the left channel going to the firstStageSource/DT and the right channel to the second. If you have one StageSource/DT connected, the Helix output is collapsed to mono and fed to the StageSource/DT. Connecting an L6 LINK device to Helix automatically disables S/PDIF out and routes audio out the digital XLR connector - no adjustments of the Global Settings > Ins/Outs > Digital Audio or Sample Rate options are necessary.

[soundmodeler]

I, too, couldn't change the volume via 'Digital Out Level' when using an AES/EBU cable. Thanks, HonestOpinion, for the explanation.