Powercab USB output overload

[rwandering]

I picked up a used PC112+ the other day and have been playing around with it.  This plus the Helix creates a crazy number of permutations! 

 

I tried to record the USB output to compare the speaker emulation out of the cabinet with the emulated output.     

 

The weird thing is that the USB output is redlining. Where I am only getting an occasionally yellow LED on the PC, I am getting frequent digital clipping from the USB.  

 

I have tried both normal and processed output, no difference.  I then connected an XLR cable from the PC to my audio interface (and set for mic level output), and I'm seeing a more moderate signal.

 

This is the firmware 2.00.1, but it seems like a firmware defect to me.  

 

Anybody else have this experience?   Am I doing something wrong (I hope)?

[rd2rk]

In Powercab System Settings, set Input 2 = Monitor; USB Mode Normal.

In your DAW, turn OFF Input Echo (track Monitor), and monitor your recording direct.

 

Edited December 4, 2020 by rd2rk
bad info

[rwandering]

Thanks for the suggestions. 

 

Playing with the Input 2 mode only makes a difference this if I set it to USB, in which case I get no signal.

The USB Mode of Normal/Processed makes no difference.

 

I guess the question is: should I expect the USB output to be usable if I follow the guidance on the input signal (i.e., targeting that the LED gets to yellow)?

 

I just did a simple test comparing the XLR output (using line level and no gain in my interface) to the USB output (with the USB in Processed mode). 

 

At -12 DB on the XLR output I get a 0 DB on the USB. 

 

At this point, I'm guessing this is intended behavior, but I can't for the life of me figure out why it would be desirable.

 

 

 

 

[rd2rk]

Having had time to RTFM (BAD RD@RK! RTFM FIRST!) I've edited my initial post to reflect that.

 

Attached is a screenshot of the settings required to NOT redline.

 

I recorded tracks using the Powercab ASIO and the Scarlett ASIO.

 

The only changes I made were in LIVE when I changed the ASIO from PC to Scarlett, to reflect the different cable routings.

 

The only way I was able to get it to redline was to change the USB Mode to PROCESSED and activate the Input Echo (Track Monitor) in LIVE. The USB MODE PROCESSED setting causes the return from the DAW to be re-processed (which is not what you're after) and fed back to the DAW which, when the Input Echo is ON results in a feedback loop, which is what the redlining is. In any case, you don't want the Input Echo on, as you're monitoring direct through the Powercab.

 

Input 2 MONITOR takes signal from an ouput on the Scarlett (when using the Scarlett ASIO) and feeds it directly to the PC power amp/speaker without re-processing it.

 

One thing that confuses some people is recording Input levels. Using USB, with the BIG KNOB on Helix maxed or disabled, gives a recording level of approx -18 to -12db. This is as it should be to allow headroom to accomodate peaks and for further processing within the DAW. When using an external AI, USUALLY if the Channel Level on the AI (Scarlett in this case) is set to 0 (all the way left/off), that's Unity, 0.0db INPUT level to the AI. You can increase that to record a stronger signal, but the closer you get to 0db in the DAW the more likely you are to get distortion on the track.

 

 

 

[rwandering]

Thanks for your help with this.  My settings are the same as yours except for one major difference -- I'm trying this with a speaker model, not Flat.  When I go Flat, I don't redline.  

 

There is no monitoring going back to the PC.

 

I've captured the waveforms below.  This is kind of meaningless in that I don't expect the XLR out and USB to be at the same levels, but the XLR output is usable, the USB isn't. 

 

 

 

Does using the Vintage speaker model make a difference?  This is how it is set for me (this is just the default).

 

 

 

And with full disclosure, I am increasing the level from the Helix to the PC.  This is so I get some of the yellow LED when strumming the guitar.  From what I've read that's what you need to do to get the best sound out of the PC.   This was all just intended as a test, but when I'm doing recording while playing through the PC, I'd rather record that emulation than use a separate speaker cab from the Helix.  Of course, different blocks and gain staging will of course impact the desirable level to the PC. 

 

Assuming you can reproduce this with a speaker model -- still a question of course -- my conclusion is that the PC isn't designed to sound its best *and* record through USB at the same time.  Perhaps if I turn down the levels to the PC I'll get less desirable sound out of it but get a good USB level (assuming the speaker and mic modeling are linear).    I'll have to test lowering the volume, but my hope was that I could follow the advice on the yellow LED and record.

 

 

If you have other thoughts about this, they are much appreciated.

 

Thanks again!

 

[rd2rk]

I TOTALLY disagree with your conclusion!

 

OK, here's my test. Attached is the preset I used, and below is a screenshot which I'll explain.

 

First, the test preset. Simple - amp, cab, IR. The IR loaded on Helix is the same IR as on the Powercab. All defaults, except I increased the Output Block level till it hit the red on Powercab (+6.0db) then backed off .5db so that hitting big power chords HARD it was in the yellow, but only VERY occasionally hit the red. That's what I recorded, BIG POWER CHORDS hit HARD!

 

In the screenshot:

Track 1 is the Helix cab - 412 Greenback25/57.

Track 2 is the USER IR on the Powercab - OH 412 MBRW GNR/57. Another Greenback 25.

Track 3 is the same IR, but loaded on the Helix.

Track 4 is the Green Speaker at -14db (Powercab default).

Track 5 is the same speaker at -20db

 

Recording was done while Direct Monitoring on Powercab. It sounded exactly the way I'd expect it to sound in every configuration. Different but good.

The recordings, played back thru the Powercab, sound just like the direct monitoring sounded. The overdriven Speaker at -14db (track 4) may have been distorting, but I couldn't really tell, since I was using the Revv Purple? I don't think it was, but at that level, it's pretty useless for a real world recording, and I've spent too much time on this already without repeating the exercise with a Clean Preset. Knocking back the Speaker Level on the Powercab 6db (to -20db) puts it right in the zone.

 

CONCLUSION:

 

It sounds great, it records great, and if the Speaker signal is too hot, just decrease the speaker level on the Powercab.

 

It's late. I'm tired. I work tomorrow. I sleep now.

 

 

 

 

 

 

rwandering.hlx

[rwandering]

Thanks for putting this effort into this.  Track 4 certainly looks overloaded, but assuming there is a lot of compression in the Revv Purple, maybe not.  It does seem that I need to turn down the input into the Powercab.  I'll play with it some more.  Thanks again! 

[rd2rk]

IT'S NOT THE INPUT INTO THE POWERCAB!

Sorry for yelling, but the whole point of my test was to show that it's the OUTPUT LEVEL to the DAW that causes the problem. Track 5 was IDENTICAL to track 4 except that I turned down the USB Speaker Output Level from -14db to -20db. That does NOT change the audible level when direct monitoring, just the level sent to the DAW over USB, or XLR when using an external AI or going to FOH with the XLR Out.

[rwandering]

1 hour ago, rd2rk said:

IT'S NOT THE INPUT INTO THE POWERCAB!

 

No problem, I can take fierce conversation!

 

So clearly I was being dense here, but I get it now.   

 

The PC editor calls it "Level" and the manual calls it "Volume".  My assumption -- and yes, I know what happens when I assume -- is that "Level" modified the signal coming in, but RTFM  makes it clearer that this is output.  I'd love a signal flow diagram for the PC.

 

I expect this Level parameter impacts both XLR and USB output.  That said, I would still expect similar levels between the two.

 

Thanks for your help -- I appreciate your efforts!

[rd2rk]

5 hours ago, rwandering said:

I expect this Level parameter impacts both XLR and USB output.  That said, I would still expect similar levels between the two.

 

 

It affects:

 

The MAXIMUM output of the cab itself. IOW, if, at the default settings (-14db) you max out the VOLUME knob and think "It's not loud enough", remember that you have another 20db in reserve! This tricks a lot of people who think the PC isn't loud enough. 20db is A LOT!

 

It also affects BOTH the XLR and USB outs. "Similar Levels" in this case is meaningless, as what you need depends on the end device being used. The USB level you need for a proper signal in your DAW may not be the same as the level needed for the same result in a DAW being fed through the XLR Out and another AI's preamps. I agree, it SHOULD be, but I also believe that I should be taller.

 

EDIT: I know I said in the previous post when I was yelling, that the level out didn't affect the audible output of the cab. It does, but you can compensate for that with the VOLUME knob, which does NOT affect the USB/XLR outs. That's what makes it useful as a dual purpose stage monitor and FOH feed, you can adjust stage level with the VOLUME knob WITHOUT affecting the level of the XLR Out to FOH. 

[rwandering]

So, Line6 support confirmed my original hypothesis (but aren't calling it a bug):

 

Quote

 

The LED on the powercab is really just for input level monitoring, but it will obviously effect that way the Powercab performs.   

 

Here is what the manual states:

 

"Indicate the overall level of the sound as it is processed through the system. Green indicates the presence of an input signal, yellow indicates that it is approaching the upper limit, and red indicates clipping. If you encounter clipping, try turning down the level of the source device (e.g., your amp modeling device) When the signal LED(s) turn yellow, the Powercab speaker system will have the most realistic non-linear natural breakup characteristics".

 

So if you want the characteristics of the yellow LED signal, then you'll need to turn it down within your DAW. I don't think there is a way around this otherwise. Maybe a output control would be good suggestions for our IdeaScale page.

 

 

Note that the support person said "turn it down within your DAW", but its too late for that . . . its overloading within the PC.  In other words, the levels are all pre-processing.

 

There already is an ideascale item on this:  

 

https://line6.ideascale.com/a/dtd/Level-control-AFTER-the-virtual-microfon-for-XLR-Out-FOH/961037-23508#idea-tab-comments

 

Please everybody vote for it!  It has hardly any votes!

 

Thanks,

Robert

 

[rd2rk]

If you came here from Ideascale, WELCOME!

 

I started this test by creating a simple preset - Princess amp, OCD, stock Helix 412 Greenback 25/57 cab. The only change from stock settings is the Output level on the OCD, to keep the overall output level even. The preset's output levels are optimized to be firmly in the yellow (not Red) on the PC's Input LED when hitting BIG POWER CHORDS REALLY HARD!

 

Using the Looper I recorded 4 tracks over USB with PC as AI -  two tracks using the PC Speaker Emulation Mode (no Helix Cab) and two tracks using the Flat Mode with the Helix Cab.

For each Mode, one track was recorded using the Powercab default Output levels, and one using a lower level to demonstrate the difference that the Output Level setting makes in the final recording. Halfway thru each track I engaged the OCD. That's the first image.

 

The second image is the same procedure using the XLR Out to a Scarlett 18i20 with the input level at 0db.

 

Again, for each mode there's two tracks, the only difference being the Output level set on the Powercab.

 

As you can see from the Track names, the different modes work within different db ranges, but the principle is the same. If the signal is too hot, turn down the Powercab Output Level, NOT THE PRESET OUTPUT LEVEL!

 

TL;DR - Optimize the Powercab's INPUT LEVEL from the PRESET, then use the Powercab's OUTPUT LEVEL settings to control the level sent to your DAW.

 Lastly, the Powercab's VOLUME knob has NOTHING to do with the USB OR XLR Output levels, it ONLY controls the level that you hear from the cabinet.

 

 

 

[rwandering]

The entire premise of my issue is that when the "signal LED" is yellow, the USB can be overloaded.  Reducing the "Level" will impact the USB output, but this also lowers the signal into the speakers.  It should be possible to independently control these.  The fact that you can do this to your liking doesn't mean it isn't a design flaw.

 

My previous acquiescence on this point was based on my being new to the Powercab.  I'm certainly not new to DAWs, modelling, nor troubleshooting.   

 

I do not dispute your ability to fine tune the PC to your liking.  I appreciate your help here, but you seem intent on disputing my desire to have the flexibility to do so to mine.  It doesn't do what I think it should, and its your right to say it shouldn't do it but I can't for the life of me understand the rationale for that.

[rd2rk]

10 minutes ago, rwandering said:

The entire premise of my issue is that when the "signal LED" is yellow, the USB can be overloaded.  Reducing the "Level" will impact the USB output, but this also lowers the signal into the speakers.  It should be possible to independently control these.  The fact that you can do this to your liking doesn't mean it isn't a design flaw.

 

What you're asking for is for changes in the XLR/USB/Mode Output levels to be independent of the Cabinet output level, and for that to be solely controlled by the VOLUME Knob. Yes?

 

OK, THAT is a NEW FEATURE request that you could make on Ideascale and I'd vote for it! 

 

If you read back through this thread, we started out trying to get a proper recording level AND a proper Input level at the same time. We went through multiple issues before we got down to the real problem. It's only now that we've accomplished that, that you've isolated a whole different, but valid, issue. Again, post it, I'll vote for it!

 

FWIW  - Sorry, but the Ideascale link you referenced that I down-voted ( I RARELY do that!) was NOT related to ANY of the issues we dealt with, and was in fact a bunch of confused nonsense. I just re-read it and STILL have no idea what he's talking about!

 

 

[rwandering]

Actually no, I never said I wanted the volume knob on the cabinet to control the output of XLR/USB.  

[rd2rk]

8 minutes ago, rwandering said:

Actually no, I never said I wanted the volume knob on the cabinet to control the output of XLR/USB.  

 

And there lies the reason why it's taking us so long to sort this out. You and I don't communicate in the same languagel!

 

I never said that you ever said that you wanted the Volume Knob to control the output of the XLR/USB!!!!!!!

 

I said that what you wanted was for the XLR/USB Output levels to be independent of the Cabinet Output level, WHICH IS CONTROLLED BY THE VOLUME KNOB!

 

To put it another way - If one changes the USB/XLR Output Level, it SHOULD NOT affect the CABINET OUTPUT LEVEL (which it currently does), so there'd be NO NEED to COMPENSATE for those changes with the VOLUME KNOB. Completely independent.

 

Post it, I'll vote for it!