Baffled - Turning up Powerstage volume is lowering Helix LT XLR out....

[gabeausiello]

Hello everyone. Coming here for help. I have a Helix LT. I love it. Started having this really odd issue that leaves me completely baffled. My patches run dual paths so that I can run to front of house with Cab IR and also into my Seymour Duncan Powerstage 700 for my cab (non-IR). The Powerstage gets the left/mono 1/4" out, and the mixer gets the left/mono XLR out.

Now, here's what started happening.... when I turn up the volume on my Powerstage, it is lowering the signal coming from the XLR out in the Helix. It is visible on the meter in the mixing board. I discovered the issue because I have guitar coming to me into my in-ears and when I was turning up my amp, it was being lowered gradually as I turn up my Powerstage.

So, how is this even possible? How would the Helix even know or detect what the volume is on whatever poweramp the 1/4" out runs to? Initially thought it could have just been phase cancellation but again, you can visibly see the volume going down on the mixer meter(s).

Hopefully I've described my issue well enough and with enough details.

Few more details:

-If phantom power was being sent, and I confirmed it is not (I've read Helix does weird things with phantom power)
-I don't know when this issue started
-I have not reset the Helix or anything yet
-It occurs on all of my banks/patches

Thank you in advance for your help.

[rd2rk]

The only way I can see that happening is if there's a channel compressor on the mixer channel.

If the LT was lowering its output, then that would be visible on the LT's Output Block meter.

 

[gabeausiello]

Thanks. I need to check again, but if IIRC I did check that and it was not visibly lowering the output on the Helix meter.

No compressor on the mixer channel.

I did also unplug my speaker output from the Powerstage and test, and it did NOT lower the XLR volume as I turn up the PS volume. It only occurs when the Powerstage is pushing hard. Does the Helix have some sort of way to measure current draw through the 1/4" output? Even if it did, I still don't understand why it would lower the signal to the XLR out.

 

[rd2rk]

Not sure if it applies to the powerstage, but most amps will compress when pushed.

[gabeausiello]

Yes. For sure. I just don’t see how that has any effect on the signal volume from my XLR out when it’s on a completely separate path and output. It’s so strange.

[Schmalle]

Fun stuff. I doubt that the Helix changes level on the XLR because I also don't see a plausible explanation. But I love to learn and be proven wrong.

 

To investigate this further:

Does it also happen when you crank the Power Stage without a connected speaker (it's class D so you can safely do that)?

 

This test excludes the mixer and your perception from the list of possible causes:

Put a patch with just a Synth -> 3 Note Generator block in it and record the XLR Out with an external interface while increasing volume on the Power Stage. Is the level decreasing in the recording?

[silverhead]

You could also experiment with the LT volume knob. In Global settings you can assign it to control only one of the 1/4" or XLR outputs. Can't imagine this would affect anything but we're into seemingly inexplicable territory here.

[gabeausiello]

On 10/15/2024 at 3:24 AM, Schmalle said:

Fun stuff. I doubt that the Helix changes level on the XLR because I also don't see a plausible explanation. But I love to learn and be proven wrong.

 

To investigate this further:

Does it also happen when you crank the Power Stage without a connected speaker (it's class D so you can safely do that)?

 

This test excludes the mixer and your perception from the list of possible causes:

Put a patch with just a Synth -> 3 Note Generator block in it and record the XLR Out with an external interface while increasing volume on the Power Stage. Is the level decreasing in the recording?

Exactly! There is no plausible explanation. I'm good with things like this, as well as two of the others in my band (one is a sound engineer) and we were all completely stumped as to how it's even possible.

To answer your question, "yes", I did disconnect the speaker cable and all was fine when I turned it up.

I will attempt your test idea and report back. Thank you for the suggestion! It's going to drive me nuts until I figure it out.
 

 

On 10/15/2024 at 7:07 AM, silverhead said:

You could also experiment with the LT volume knob. In Global settings you can assign it to control only one of the 1/4" or XLR outputs. Can't imagine this would affect anything but we're into seemingly inexplicable territory here.

Yes. I was going to mess with that more as well just for testing purposes. I believe I did set the volume knob to only control either the XLR or the 1/4" and had no change, but I was also flustered and frustrated when testing so I can't fully remember. lol! Thanks for your input.

[theElevators]

Something is wrong with the power amp.  It probably sends the current back to the Helix somehow, and that causes the XLR output to malfunction??  Or maybe it's taking up so much juice that there is not enough power left for the Helix.  You know how when you turn on your AC at home, your lights get dimmer?  lol

 

As a software developer would, test out all the following:

1. change the 1/4" cable

2. try using a regular guitar combo amp instead of a power amp, see if the same thing happens. 

3. Try ground lift.

4. Try having power amp and Helix be on different power sources, or different rehearsal space. 

 

[gabeausiello]

On 10/15/2024 at 11:10 AM, theElevators said:

Something is wrong with the power amp.  It probably sends the current back to the Helix somehow, and that causes the XLR output to malfunction??  Or maybe it's taking up so much juice that there is not enough power left for the Helix.  You know how when you turn on your AC at home, your lights get dimmer?  lol

 

As a software developer would, test out all the following:

1. change the 1/4" cable

2. try using a regular guitar combo amp instead of a power amp, see if the same thing happens. 

3. Try ground lift.

4. Try having power amp and Helix be on different power sources, or different rehearsal space. 

 

Thank you for all those suggestions. I haven't tried changing the cable yet - in fact, there is a short "L angle" cable that I am running directly into the PS that I connect my longer cable to. I need to remove that as well. I will try another amp. I did use the ground lift on the Helix (not sure if the PS has one but I'll check). I was running the Helix out of the same power conditioner, and did try going straight to the outlet, BUT both devices were technically still on the same outlet. I'll try changing that as well.

I will keep this thread updated with my findings. Thank you all for the information.

[gabeausiello]

OK. Did more testing last night. I initially chalked it up to phase cancellation, but it's definitely not.

-It's not the cables (used different ones)
-It's not the PowerStage (I tried a Quilter we have)
-Power sources were different
-We can see the volume gradually dropping 15-20 db on the meter in the mixing board when I crank the amp all the way.

I ran my in-ear module straight from the XLR out of the Helix, and the issue was definitely occurring. At this point, I have to say it's the Helix. I'm going to backup/factory reset after my next round of shows. We'll see if that fixes the issue, but I'm not hopeful. Still going to experiment with a couple of small things, such as the power cord I'm using from the Helix to my SKB PS-45 power supply (it's in a 120v socket, NOT the pedalboard onboard pedal power connections which obviously don't have juice to power a Helix). Definitely going to test the sockets with a multimeter though, just to rule that out too. Even with that, I still can't see how the issue would be caused by it. I also forgot to try the synth patch mentioned above. I will try that as well if the reset doesn't resolve it.

Thanks again, everyone. I'll keep the thread updated.

[rd2rk]

Again, what about the Helix Output Block meter? That really is the best way to tell if it's the Helix.

What do you mean by "when I crank the amp all the way"?

If you're cranking the amp's MASTER, then you could be hearing the natural compression of the amp's power tube emulation.

Although, 15-20db does seem a lot. Does it do the same thing when you use the Channel Volume or the Output Block Level?

I'm really just spit balling here. This is a behavior I've never seen anyone else report before.

[amsdenj]

Your initial diagnosis may be correct, the overall volume is going down because of phase cancellation. That would show on the mixer meters and in your IEMs if your backline is out of phase with your FHO speakers. Flip the phase in Helix or at the mixing desk and see if the problem goes away. 

[datacommando]

On 10/18/2024 at 2:03 AM, gabeausiello said:

I ran my in-ear module straight from the XLR out of the Helix, and the issue was definitely occurring.

Hi,

 

This seems to be baffling all the usual forum gurus, and personally I’m also baffled by what you are describing. Thus far, most focus has been put on the SD Powerstage, mixer and the Helix LT. 

 

Although, I don’t use them (hate the things), and have no personal experience of IEM, I have seen them mentioned in a couple of the posts in this thread. There is no mention of any specific brand, and/or how they are connected to the signal flow. It’s my understanding that, generally, IEM are fitted with some sort of limiter to protect the user’s hearing.
 

If the IE monitors are the single common factor and have been in use throughout all your tests, then I would be tempted to check out if those are the culprit? It’s the only thing that comes to mind, as the more you crank the input the more gain reduction would be applied to protect your hearing.

 

Hey - just throwing it out there. Possibly as far off the mark as everyone else!

 

Hope this helps/makes sense.

[Schmalle]

I think the power amp is not connected to earth and by this is able to shift ground with power.

 

Check the rehearsal room's power sockets for a proper earth connection and all power cables for proper ground connection.

[gabeausiello]

On 10/17/2024 at 9:40 PM, rd2rk said:

Again, what about the Helix Output Block meter? That really is the best way to tell if it's the Helix.

What do you mean by "when I crank the amp all the way"?

If you're cranking the amp's MASTER, then you could be hearing the natural compression of the amp's power tube emulation.

Although, 15-20db does seem a lot. Does it do the same thing when you use the Channel Volume or the Output Block Level?

I'm really just spit balling here. This is a behavior I've never seen anyone else report before.

Sorry, I mean the volume of the powerstage. No tubes. 

[gabeausiello]

On 10/18/2024 at 6:20 AM, amsdenj said:

Your initial diagnosis may be correct, the overall volume is going down because of phase cancellation. That would show on the mixer meters and in your IEMs if your backline is out of phase with your FHO speakers. Flip the phase in Helix or at the mixing desk and see if the problem goes away. 

I did try on the Helix when in-ears were directly connected. No change. 

[gabeausiello]

On 10/18/2024 at 6:31 AM, datacommando said:

Hi,

 

This seems to be baffling all the usual forum gurus, and personally I’m also baffled by what you are describing. Thus far, most focus has been put on the SD Powerstage, mixer and the Helix LT. 

 

Although, I don’t use them (hate the things), and have no personal experience of IEM, I have seen them mentioned in a couple of the posts in this thread. There is no mention of any specific brand, and/or how they are connected to the signal flow. It’s my understanding that, generally, IEM are fitted with some sort of limiter to protect the user’s hearing.
 

If the IE monitors are the single common factor and have been in use throughout all your tests, then I would be tempted to check out if those are the culprit? It’s the only thing that comes to mind, as the more you crank the input the more gain reduction would be applied to protect your hearing.

 

Hey - just throwing it out there. Possibly as far off the mark as everyone else!

 

Hope this helps/makes sense.

Totally get it. It's not specific to the in-ears. Just more obvious. When running from the xlr straight to the mixer, it also drops in the mains (directly in front of the speaker to confirm). It's absolutely bonkers. 

 

I still have more testing to do though. 

 

Thanks all for your responses. 

[gabeausiello]

On 10/19/2024 at 1:11 AM, Schmalle said:

I think the power amp is not connected to earth and by this is able to shift ground with power.

 

Check the rehearsal room's power sockets for a proper earth connection and all power cables for proper ground connection.

Thinking about this further, and we have had ground loop issues in the past there. They also just had a power outage (I was told not a surge) that was suspect in frying one of their computers. Everything else was fine so maybe just a coincidence. And for the record, none of my equipment was plugged in. I always pack it up after every practice. 

 

Definitely going to try this in a different space as well. 

[rd2rk]

On 10/19/2024 at 2:18 PM, gabeausiello said:

Sorry, I mean the volume of the powerstage. No tubes. 

I meant the Helix emulation of the amp’s power section which is controlled by the MASTER parameter. This is probably not the problem, but at this point I’m out of ideas. Good Luck!

[gabeausiello]

On 10/20/2024 at 2:11 PM, rd2rk said:

I meant the Helix emulation of the amp’s power section which is controlled by the MASTER parameter. This is probably not the problem, but at this point I’m out of ideas. Good Luck!

Ah. Got it. Yeah man. This is a weird one.