zappazapper

Ya, I get that a lot XD but hey, just so you know, part of the reason I'm probably overthinking it IS that I'm interested in the science and engineering part of all this, not just so I can get "good tone" but also just for the sake of knowledge. And if I sound (read?) like I'm trying to find holes in your responses just so that I can win an argument, I apologize, because I'm really just trying to learn about this stuff. That's why I keep asking "why?" every time you answer my last "why?". Hope you understand. Hmm. So ya, that's something that doesn't fit with my own understanding of what a guitar preamp does. I mean, a guitar preamp is not that different than a mic preamp, and a mic preamp (generally) takes a low-level high-impedance signal and amplifies it to a high-level low-impedance signal, right? So I guess I made an assumption that a guitar preamp also does that. And I had to take a look and remind myself what the "Instrument/Line" option is on the Helix: It's an option for the complete loop. There's no separate option for the Send and another for the Return. And assuming that L6 knows that a good percentage of users will be using the loop for 4CM (I mean, it's in the manual), clearly they would have provided separate options for the Send and Return if it was necessary. https://www.zikinf.com/manuels/cornford-roadhouse-30-head-manuel-utilisateur-en-32271.pdf OK so this is where I'm getting confused, and it's not just because the concept of mismatched impedances having an effect on frequency response makes sense to me, but because I have my own anecdotal experience with impedance mismatches having an effect on frequency response: back when I started experimenting with 4CM, I had an X3 Live. http://www.benvesco.com/blog/the-digital-age/2007/pod-x3-specs-revealed/ https://www.soundonsound.com/techniques/understanding-impedance When I connected the X3L and the amp in 4CM, the tone was "screamy", for lack of a better word. It certainly had more gain, but when I tuned the Send Level in the "Loop" Block down to a point that I know had less gain than the amp should have had at that setting, it still had this screamy character. And so after some research I learned about impedance mismatching, and considering the values that I quoted, it made sense to me that the impedance mismatch between the FX Send of the X3L and the front panel input of my amp was resulting in an increase of high frequency content (or more correctly, a LACK of high-end roll off associated with high impedances, which a guitar amp preamp is specifically designed to compensate for), resulting in the "screamy" character I was getting. And so the solution seemed to be a reamp box, since reamp boxes are designed to convert low-impedance "line-level" signals to high-impedance "instrument-level" signals. And lo and behold, after I bought this... https://artproaudio.com/framework/uploads/2018/06/om_dualrdb.pdf ...all of a sudden my amp sounded exactly like my amp again. Now, when I started looking into the Helix line, I noticed this "Instrument/Line" option for the FX Loops and figured that L6 must have had enough feedback about the impedance issue to include circuitry that would deal with it, but when I got my LT and connected it in 4CM with my amp without the reamp box, I got the same screamy tone regardless of what setting I used. Which is why I've mentioned in numerous places on the forum that I'm not sure the "Instrument/Line" option does anything to the impedance of the signal coming from the Send. Now you're saying the impedance of the Loops are 1M, regardless of the setting. Again, not to question your credibility, but I'd really appreciate if you could provide a link to where you got that information because I can't find it. At any rate, if it was 1M, it wouldn't explain why I still get that screamy tone from my amp in 4CM without the reamp box. 1M would seem to be a better impedance match with a front panel input on a guitar than the 100k of the X3L, and certainly shouldn't result in an increase in high frequency content. I'll have to test that out again on my rig. Confirmed. I think what I'm trying to say is that I'm more concerned about the impedance portion of "line-level" and its effect on frequency response. Signal level can be easily dealt with, and it wouldn't even offend me if it were some arbitrary setting on a digital level control in the Helix. But yes, I can confirm that the level coming back from the preamp is about the same as having the Loop block bypassed. Sorry, I just can't see how a compressor between a preamp and a power amp would be such an uncontrollably disastrous thing. In fact, I use one often. In fact, my X3L had a unmovable LA-2A model right after the Loop block in the "Pre" position, which is where I always used it (after gate, wah, distortions, before EQ, before mods, reverbs, delays in "Post" position), which I used often. Again, one has to be careful with a compressor REGARDLESS of where it is in the signal chain. I made sure it worked. Anyway, at this point, I have more questions than answers. That's fine. It usually means I'm about to learn something. Unfortunately, I'm too tired for a night of deep-diving my gear. I appreciate your responses and I look forward to more.

Awesome. I'll have to read that article about 100 more times before I understand it, but ya. That should work. I'd also like to test the Helix's loops and outputs because I've never really seen a clear answer as to whether the Instrument/Line settings actually do anything as far as impedance goes.

If your amp was sending a line-level signal to the Helix and the loop on the Helix was set to receive line-level signals, why would it overdrive the Helix? How did you reach this conclusion? Because the manual for your amp says the loop is instrument-level? What amp are you using?

Fair enough. I don't know if there was a multi-fx in existence that had its own effects loop that would allow you to place some effects before the preamp and some after when this amp was designed (late 80s). I will disagree with you about using compressors in the loop, though, although clearly one has to be mindful of the output level. So from what it says there, would you say it's an instrument-level loop or a line-level loop?

I think I get what you're saying. You want another organization level ABOVE Presets, where a Song could potentially call up any number of Presets, and a single Preset could potentially be assigned to multiple Songs, and making changes to that Preset would carry over to ever Song that uses that Preset. I love it, but... At the risk of insulting the typical user here, I'll say that the kind of control you're talking about is not likely to happen. The features included in the Helix are largely dependant on the collective wishes of the users of this forum, and even more so the "voting public" on Ideascale. I've submitted a few of my own "control-centric" ideas and haven't received nearly as much support as things like "more, better reverbs" and "polyphonic shift" (I will admit I'm glad that got done) and "this amp model" and "that amp model". So those are the kinds of things L6 prioritizes, as they should if they want to keep the majority of the user base happy. What I'm saying is that the Helix is flexible enough to do what you want, it's just not going to happen the way you think it's going to happen. I also play in a cover band that plays a bunch of different songs by a bunch of different artists that often have multiple discrete sounds per song, and we also don't really use a predetermined set list. Your idea would really benefit me, but it's not gonna happen so this is what I do. I have one Setlist that I use for building Presets. In this Setlist the order doesn't matter because I don't use them during a performance, only when I'm tweaking on my own or during rehearsal to make sure they sound the way I want and because I have more time to get from song to song. Now, because of the pandemic I haven't gigged with my Helix yet (got it in November I think?), but the plan is, once I'm happy with the Presets I've built, I copy them to another Setlist that is for live performance. Whether they're sorted alphabetically or some other way (we do 3 or 4 song "mini-sets" of songs by one particular artist, one after another quite often), they're renamed as I copy them to this new Setlist so that they have some context to the actual performance (could be a band name, could be a song name), rather than the name I use as I'm building them, which usually has more to do with what's going on "Block-wise" in the Preset. The Presets in the "build" Setlist will often be copied to multiple Presets in the "performance" Setlist. If I need to make changes to a Preset, I make changes in the "build" Setlist then copy and rename them to the "performance" Setlist. So ya, in terms of what I have to do during non-performance time, what I'm doing takes way longer than what you're suggesting, but in-performance it works exactly how you describe: I have a bunch of different Presets that represent songs that are ordered in some way that makes it easy and fast to find the next Preset I need, whether it's been decided beforehand or not. I think this is the best you're gonna get with the Helix, without some piece of external equipment. You can sign up for an Ideascale account and submit your idea and I'll vote for it (please post a link if you do), but in my experience this kind of "control-centric" idea doesn't get far in the community. Hope this helps.

My question is WHY are you using instrument-level? Do you know for a fact that your amp's loop is instrument-level? Or is it a purely sonic reason? If it is, is there an obvious issue with using line-level, like some kind of audible distortion, or is it a purely subjective choice? "It just sounds better"? Provided you know whether your amp's loop is instrument-level or line-level. Check out the contradictory pile of garbage going on in the manual for my amp. https://mesa-boogie.imgix.net/media/User Manuals/50 Caliber Plus.pdf From page 4: "EFFECTS SEND & RETURN These jacks provide a low-noise patch loop within the 50's preamp for connecting external accessories. Compatibility is quite good with most line-level or rack-mount devices..." Quite good? If it were line-level, wouldn't compatibility be PREFECT?! "...although some will require you to trim down their input attenuators to prevent overload." OK so then line-level signals are too hot, so that must mean the loop is instrument-level. Right? "(Pedal-type effects are designed to handle the low-level signals emanating directly from your guitar; therefore this type of device should be connected “in front” of the amplifier, rather than in the Effects Loop.)" OK, so the loop isn't instrument-level either? Ffs. "Some manufacturers offer rack-mount multi-effects units for guitar which include compression, distortion, overdrive, etc. Although a good-quality compressor can be used effectively in your Boogie's Effects Loop, we do not recommend the use of multi-effect "guitar processors" in the Loop, as their inputs are often too sensitive and their added gain stages will tend to contribute some noise. If you wish to use this type of device with your Boogie, it should be patched in between the guitar's output and the amplifier's input." K wait. You just said that pedals should be plugged into the front panel input because pedals have "low-level" (instrument-level?) signals, and now you're saying multi-fx units should be plugged into the front panel because their signals are too hot for the loop. So ya, there's really nothing I can gleen from the manual on this subject. Which is why I'm after a way to test it myself.

Apologies if I've already asked this question... https://line6.com/data/6/0a020a4112bbf5fb6a519e8b18/application/pdf/HX Stomp 3.0 Owner's Manual - Rev C - English .pdf I don't own a Stomp, but before I got my LT I was looking at all the manuals for the different products in the Helix lineup, and I was reminded of this today when I was checking the Mesa Boogie Board to see if there was any new responses to posts I've made there. From page 9: This is contrary to my own understanding of what a guitar amp preamp does. It seems to me that, besides shaping the signal coming from the guitar, the job of a preamp in a guitar amp is to bring the level of an instrument-level signal to line-level. And so what comes out of an Effects Loop Send on an amp would be line-level, and what an Effects Loop Return would expect would also be line-level. So I have a few questions: Is this a typo in the Stomp manual? Are most effects loops indeed instrument-level? Is there a way to use a multimeter to find out the signal voltage and impedance of different points in the signal chain of an amplifier?

My only conclusion is that this seems to be unity gain on the Helix, with no Blocks enabled and Input and Output Block gains at unity - ... at least, that was the setting that gave me the same level of signal as if the Helix wasn't part of the signal chain at all. The more I think about it the more I wonder if it was worth the effort to include the graphs, as I was really only using them to spot major issues that would suggest a bad connection, etc. At the end of the day, every power amp is going to have its own frequency response and distortion characteristics, and that's part of the trade off with 4CM (which is the same reason I took the speaker out of the equation entirely) and it was never my intention to find a way to counteract that, and I wonder if including the graphs gave the wrong impression of what I was looking for. I was only ever looking for the VOLUME setting on the Helix.

I wasn't necessarily looking for the point at which the input of the power amp would clip. What I was looking for was a level setting that would be the same as not having the Helix connected at all, so that the behavior of the amp would be more or less the same as if I was just using the amp. My basic building block Preset has just the FX Loop 1 block and I wanted that to sound the exact same as just using the amp without the Helix, and then build off of that. You have a point about the range of the response graphs, although I was really just using them to detect MAJOR problems that would show up even at this extreme range. Wouldn't using a sine wave at a particular frequency only tell me about the behavior at that frequency? That's why I used a sweep, so that it would tell me about the behavior at all audible frequencies. Can you expand on that a bit? I have yet to read anything that suggests that it is possible to completely bypass the A/D and/or D/A conversion stages on a Helix. Where does it say that?

I think you misread the OP. He doesn't want to control external devices with MIDI. He ultimately wants to do everything with the Helix, and MIDI only became part of the conversation when it was suggested that an external MIDI controller might be the only way to have things work the way he wants. So yes, Command Center might be the answer, but more for setting up Stomp Footswitch mode to call Snapshots or even other Presets, not necessarily for sending MIDI to control external devices.

Helix Floor manual - https://line6.com/data/6/0a020a4112b165fb6a3fe41663/application/pdf/Helix 3.0 Owner's Manual - Rev E - English .pdf From page 9 - "18. EXT AMP 1/2 Connect to your traditional guitar amp to switch its channels or turn its reverb on and off. Use a TRS cable for dual operation (1=tip, 2=ring)." In order to switch two amps, you need a TRS to dual TS splitter.

I think it's a valid argument that objective, easily defined facts can be useful in trying to find some subjective quality that can't easily be defined. I mean, even L6 didn't boil this stuff in a cauldron. They used science and engineering to create sounds that are pleasing in an artistic way. I don't see why anybody has to be tied to one or the other. I don't think about phase response graphs when I'm playing, but stuff like that can tell you something when you're not hearing what you think you should.

Having each amp controlled by a separate Ext Amp doesn't preclude you from being able to switch both amps' channels simultaneously, just like you can control multiple blocks simultaneously. There's a couple ways you could do it - if you wanted to do it per-Preset, you would use Command Center. If you wanted both amps on clean channel, you leave the Instant Commands blank. If you wanted both amps on dirty, you would assign Instant 1 to ExtAmp 1 and Instant 2 to ExtAmp 2 if you wanted to do it using Snapshots, you probably have to assign each ExtAmp to a separate Stomp Footswitch, since you can't assign multiple ExtAmps to a single footswitch or Instant the same way you can with block bypass or control assign. Once you have the Ext Amps assigned to the footswitches, you use Snapshots to change the state of both footswitches I just think it's an easier, more reliable way to do it compared to having to have the amps on a common ground and all that business, because you never know what kind of disastrous situation you're going to walk into in terms of on-stage power when you go to play a gig. You'd be dependent on something that you can't really control. At least the way I described would work no matter what the venue's power is like.

Ya, a bit of a long read I guess. It really only took a couple hours. Well, that's kind of the whole point. I don't know what your experience with 4CM is/was, but for me it sounded better than it... uh... sounded. I mean, when I first read about it, it looked like the perfect marriage of old school, real gear and next generation technology. But when I hooked it up for the first time, the reality didn't live up to the promise. And there really isn't a ton of really in-depth information on 4CM, so I had to look into myself, with my bargain basement gear, free software, and hobbyist-level technical knowledge. And since whatever I know is what I've learned from reading this forum and others like it, I feel an obligation to pass on what I've learned, even if I have serious doubts as to the veracity of my own conclusions. I really wish someone would come on here and tell me where I'm wrong and why and how to get the right answer.

Sorry. I wanted free credibility :/

Check. You might want to make sure you understand what "Preset Spillover" is, because whether you use it will have an effect on how you build your patches to transition between songs. With Preset Spillover enabled, delay and reverb trails will continue after you have changed Presets, and there will be no audible gaps between Presets, at the cost of only being able to use one Path per Preset (it loads the selected Preset on the free processor while leaving the previous Preset running on the first processor until the next Preset is loaded and all trails have stopped "trailing" on the previous). In your case of nightly changing setlists, it might be advisable to enable Preset Spillover. If you had the same setlist every night, you could use Snapshots to cover a few songs at a time (Snapshots enable and disable Blocks and change Parameters within the same Preset, so there are no gaps and trails keep on trailing), but trying to do that with an ever changing setlist would require essentially building new Presets every night. Check. Each Setlist has 32 Banks of 4 Presets = 128 Presets. Snapshots make it so that you will rarely need more than 1 Preset per song, so 128 should be fine. Check. Press either the ^ or v switch to bring up the Preset menu. Use ^ and v to scroll through Banks. It displays 2 banks at a time. Check. The display stays in the Preset menu until a Preset is selected. Audio is not affected by entering the Preset menu. Check. I can confirm that pressing and holding the ^ or v switch displays, after a short delay, the Preset menu and scrolls through the Banks until the switch is released. Check. The Presets displayed in the Preset menu correspond to the 8 middle footswitches. Check. Pressing the Home button toggles between Signal Flow View and Performance View. Performance View has two Modes, selected by the Mode switch - Stomp Footswitch Mode and Preset Mode. However, in Global Settings > Footswitches > Preset Mode Switches, you can actually set Preset mode to display almost any combination of Presets, Snapshots, or Stomps. Personally, I have them set to display Snapshots, as accessing the Preset menu is just a press of the ^ or v switch away. Check. That's exactly what Snapshots are for. However, keep in mind that if you're going to use Preset Spillover, you only have access to half of the Helix's processing power for each Preset. In most cases this won't cause an issue but if you have a song that has, as you say, 6-ish wildly different sounds that require the Preset to have many DSP-intensive Blocks, you might have to split the song into more than one Preset. On the other hand, since you're using Preset Spillover, you have the ability to seamlessly change Presets anyway, and using Control Panel, you can assign one of your Stomp Mode switches to call up a specific Preset. Stomp Mode is actually really versatile because in addition to the Stomp switches enabling/disabling Blocks, you can also have them modify parameters, call Snapshots, call Presets, send MIDI commands, etc., and many times you can do a bunch of those things at the same time using a single footswitch. Check. You may have to bend over at the beginning of the night to press the Home button to put the unit into Performance Mode, but from there, it's all done with the feet. Performance Mode doesn't display anything about Blocks, routing, etc. It basically tells you what the footswitches will do. That's kind of what's great about Stomp Footswitch mode. Certainly the Helix having 4 Presets in each Bank is tied to the fact that it has two rows of 4 middle footswitches, but with Stomp Footswitch mode you can mix and match what the footswitches do, so you can have, say, 3 switches with Presets, two with Snapshots, and three that control stomps or whatever works for you. And if it makes any difference, you can have the Presets listed numerically (1-128) instead of alphanumerically (01A-32D). You won't have to use a spreadsheet - every Preset is named. Honestly, there are a few shortcomings to the Helix in terms of control (for instance, it's possible to have the bypass state of a block ignore Snapshots using an option called Snapshot Bypass, but if you have a Stomp footswitch set to control a block's parameters, there's no way to have the parameter ignore Snapshots), but I have to say that I think it's the best multi-fx designed yet in terms of in-performance control. I'm not seeing anything in your description of what you want to do that makes me think you can't use the Helix to do the job.

Because I didn't want someone coming at me saying "Q-Clone isn't a measurement tool". I guess I wanted some credibility?

I've seen quite a few questions on this forum about levels when using 4-cable method. Most of the answers that I've seen have been anecdotal at best, so I'm creating this thread in the interest of providing some objective information on the subject. First off, I'm not an engineer. I am an enthusiast, a hobbyist, who knows what he knows from reading articles, forum posts, and watching YouTube videos, like many of you. As such, many of the techniques that I use and conclusions that I come to might be absolutely wrong. I'm not doing this to prove what I think I know, or to prove to anybody that I know something - I'm doing this because I WANT TO LEARN. If you see erroneous information or an incorrect way of thinking about something, please let me know. But also keep in mind that I don't really value the opinions of other enthusiasts/hobbyists any higher than my own - I would love for a REAL ENGINEER to come on here and set me straight (ie. not a "recording engineer"... I'm talking about someone who has a university degree in Electrical Engineering or something... "recording engineers" are actually just technicians - they don't use science to solve problems - they operate devices designed by people who use science to solve problems... rant over). Second, my equipment is not "measurement-grade". I'm using a MOTU 896HD, a "prosumer"-grade sound interface. I will attempt, to the best of my ability, to demonstrate the limitations of this device as a measurement tool. Also, as per @DunedinDragon's advice, I downloaded RoomEQWizard (REW) as an audio testing platform. In all honesty, there's too much going on there for me to really understand completely, but I think I have enough of a handle on it to use it for my purposes. Again, if anybody has any advice on how to better use this program, I'm all ears. So basically what I'm attempting to do is figure out what the correct settings and levels should be when using 4CM. Before I go any further, I'll fully concede that the actual data and conclusions that I come up with are really only ever going to apply to MY AMP - a Mesa Boogie .50 Caliber+ 1x12" combo - for various reasons. First, it's a tube amp, and as we all know, no two tube amps, even within the same model, are really the same. Second, not every amp model is designed the same (duh). For instance, the MASTER VOLUME on my amp is post-EFFECTS RETURN. On some amps, it is pre-EFFECTS RETURN. The major difference between these types of amps as it relates to 4CM is which control is used to set the actual LOUDNESS of the amp. In my case, I would use the MASTER VOLUME on my amp, and the VOLUME on the multi-fx sets the level going into the EFFECTS RETURN of the amp. In the other case, the MASTER VOLUME on the amp (I think?) would set the level of the signal being fed to the EFFECTS RETURN of the multi-fx, while the VOLUME of the multi-fx is what one would use to set the loudness. Anyway, the point is that what I'm really trying to do here is start a conversation about ways that a typical user can use his or her own equipment to do a little investigation into how their equipment actually works, not necessarily provide hard and fast answers, because there's too many variables. Ok, so let's talk about my interface. MOTU 896HD 24 bit... up to 192 kHz sample rate (I've never gone higher than 48kHz) 8 Neutrik XLR/1/4" combo jacks for inputs, each with a sensitivity selector switch (LINE/+4/MIC) and a trim pot 8 XLR jacks for outputs, each with a sensitivity selector (-10/+4) Nothing special. Anyway, I first wanted to test the interface itself, just to see if there was anything crazy bad going on there. I connected an XLR cable between an output and an input and set the sensitivity switches on both to +4. A quick summary of what REW does - it outputs a frequency sweep to the desired output, then analyzes the signal coming back into the desired input, and displays this analysis on a number of graphs. The first step to doing a test is to set levels - REW sends a few seconds of pink noise to the desired output and then measures the level coming back. Anyway, I had assumed that since both the output and input of my interface were set to +4, that the level at the output (-12 dB) would be the same at the input, but at the input I get -14.8 dB. I've tried different outputs, different inputs, different cables, but I always get -14.8 dB. But here's the thing - ultimately I'm not going to use balanced connections in my test, because my amp only has unbalanced jacks. This is only to test the interface in as ideal a situation as possible. And also, even if the levels at the output and the input don't match, it's not important that they do, only that I know what the level coming back to the input should be. So anyway, here are the frequency response, phase, and distortion plots for this first test - The top red line in the first graph is frequency response. I'd say that's pretty flat, especially in the audible range. No issues there. The second red line is the phase. Again, pretty good in the audible range. The light brown line in the second graph is the same as the top red line in the first graph - the frequency response. The dark brown line is the noise floor and the grey line is the distortion (THD). For whatever reason this program doesn't put the legend that I see in the program, which lets you see the value at a chosen point on the graph - the point is, the distortion never gets above 0.005% THD, and at any rate, it's barely more than the noise floor, which is inaudible. OK so the second test I did is with an XLR > 1/4" TS cable connected between the output and input of my interface, because like I said, my amp doesn't have any balanced connections, so whatever is going on with a balanced signal doesn't really apply to testing my guitar rig; it was only useful to test the interface itself in as ideal conditions as possible. Basically I'm doing this test to get a target level at the input, and to make sure the frequency response, phase, and distortion are still in pretty good shape. The level I got at the input was -14.6 (I thought it would be significantly lower, but hey), and here are the graphs - No major changes between balanced or unbalanced connections, and no major problems in either than would affect the results of testing another piece of gear. Good. And now I know my target level at the input should be around -14.6 dB. Ok so now what I want to do is test the power amp of my amp. The theory here is that if I have the output of a multi-fx plugged into the EFFECTS RETURN of my amp, with all the effects bypassed, I want the level to be the same as if I plugged my guitar into the EFFECTS RETURN jack on my amp, using a DI box to make the signal line-level. To do this test, I'm connecting the output of my interface to the EFFECTS RETURN of my amp with an XLR > 1/4" TS cable, and the DIRECT OUTPUT on my amp to the input of my interface with a 1/4" TS guitar cable. The DIRECT OUT is a line-level tap off of the output transformer, and it is affected in level by both the MASTER VOLUME and DIRECT controls on my amp. What I'm looking to do is find a MASTER VOLUME/DIRECT setting that gives me -14.6 dB at the input of my interface, so that for the next test where I connect the Helix output to the EFFECTS RETURN of the amp, I'm looking for a Helix VOLUME setting that gives me -14.6 dB. The MASTER VOLUME/DIRECT settings that I find in this test are not applicable to real-world use - only for the purpose of this test. In the interest of keeping the loudness in my apartment to a minimum, and to reduce the chance of power amp distortion affecting the results, I've set the DIRECT at 10 (full) and I'm using the MASTER VOLUME to get as close as I can to -14.6 dB at the input of my interface. I ended up having to set the MASTER VOLUME on the amp at just above 1. Also, I should mention that the PRESENCE control is set to 10, which is the setting for the least amount of negative feedback (I wouldn't be able to back up the suggestion that that setting provides ZERO negative feedback, only the least). The results are interesting - Honestly, the frequency response and distortion characteristics don't bother me (it's a tube guitar amp, it's not supposed to be fidelitous) - BUT LOOK AT THAT PHASE!! This would explain why I had to rewire a speaker cable to use 7CM with my JCM900 - apparently the power amp of my amp amplifies things out of phase and my JCM900 doesn't. Weird. Anyway, for the purpose of testing, I decided I had to remedy this. REW has an option to invert the polarity. It doesn't really explain whether it inverts the signal being outputted or the signal being captured at the input. Anyway, here's the result - So, not perfect, but much better. So the next test is to connect the output of my interface to the FX RETURN of my Helix using an XLR > 1/4" TS cable, the 1/4" OUT of the Helix to the EFFECTS RETURN of the amp using a 1/4" TS cable, and the DIRECT OUTPUT of my amp to the input of my interface using a 1/4" TS cable. The Input Block for the Helix is set to Return 1 (Input Gate "Off"), output to 1/4" (Pan "Center" and Level "0.0 dB"). There are no effects blocks. In Global Settings, 1/4" Outputs are set to "Line", and Volume Knob Controls is set to "1/4"". I can't think of anything that would affect this test (at this point I'm not using the Guitar In or the FX Send so those settings are irrelevant right now). A couple thoughts about "line level" - there really is no agreed upon voltage that is defined as "line level", as far as I can tell. There's a range. I doubt that L6's line level is the same as what Mesa Boogie thought line level was in 1989. But in this case it's irrelevant because I'm looking for a Helix VOLUME setting that will give me as close to -14.6 dB at the input of my interface as I can get. But more importantly, "line level" is also a definition of impedance. I don't know what impedance the EFFECTS RETURN on my amp expects, what the Helix 1/4" Out sends, nor whether the LINE/INST setting has any affect on the impedance of the signal coming from the Helix at all. I suppose if there is a difference, it will show up in the frequency response graph? So first thing's first - this is the VOLUME setting on the Helix that gave me 14.6 dB at the input of my interface - I don't know if I have an opinion on this, or if I need to have an opinion on this. Having the required VOLUME setting be at full or even 12 o'clock would make me feel like I've been doing everything right and actually got a volume setting that I could use and maybe EVERYBODY ELSE could use reliably. But until I see a compelling reason why my entire thinking is wrong on this, I'll accept that this is the VOLUME setting that is going to give me the same level as if I was plugged into the EFFECTS RETURN of the amp with a DI box. And so I put a little green triangular piece of tape on my Helix to mark that setting for future reference. In case anybody's interested, here's the test results - No major changes. I'm thinking that if the impedance were wrong, there would be a big difference in the high end content, which there isn't, so I'm going to assume that there's no point in investigating the INST setting for the connection between the Helix 1/4" Out and the EFFECTS RETURN of my amp. As far as the question of level settings for the preamp of a guitar amp in the loop of a multi-fx, I don't really see how this kind of testing is relevant to this application. In the case of trying to find an output volume to feed your amp's effects return, it's a question of trying to maximize fidelity and volume (even if, in the case of my amp, the power stage of your amp isn't particularly fidelitous at all). When it comes to a guitar preamp, fidelity isn't even a remote concern. It's a tool for shaping the tone of your dry electric guitar signal (which nobody likes anyway), so even if there is a slight difference in gain or output levels between plugging your guitar straight into the front panel of your amp and putting the preamp of your amp into the FX loop of a multi-fx, you're setting that GAIN control to taste anyway, so that kind of accuracy in settings is less important than if the user can find a setting that "feels" the same as plugging straight into the front panel. And that is a question of impedance, since a low-impedance line-level signal will result (in my experience, at least) in an unbearably "screamy" sounding preamp, I'm assuming because a high-impedance instrument-level signal comes with an inherent high-frequency roll off that a guitar preamp is designed to account for. And so the Helix has a setting that seems to be intended to deal with that - the Line/Instrument settings in Global Settings > Ins/Outs > Send/Return. I've asked the question a few times but never really got a definitive answer as to whether or not this setting actually does anything to the impedance of the signal coming from the FX Send, or if it just dials down the voltage. Back in the X3 days, I started using a reamp box to convert the line-level signal coming from the FX Send of my X3L to an instrument-level signal and that made my preamp "feel" like I was plugged into the front panel when it was actually in the loop of the X3L, and so I continue to use the reamp box with the Line setting with my Helix because it just feels better than the Instrument setting. Whether or not I got the same amount of gain for a given GAIN knob setting is irrelevant, or at the very least the difference was too small for me to notice. So I don't know what there is to gain by running pink noise or a frequency sweep through a guitar preamp for the purposes of finding the "correct" settings, because there isn't a correct setting on a guitar preamp. Right? Maybe someone can give me a compelling reason why it would be worth the time and effort to do such a test. I think that if the question is whether the Line/Instrument settings actually do anything in terms of impedance, it's probably better to answer that question with a multi-meter or something, and I'm not knowledgeable enough to do that test. I might not even be knowledgeable enough to do the tests I just did. Haha. Anyway, I hope this is interesting to SOMEONE and I'm happy to see and respond to any CONSTRUCTIVE comments or questions or criticisms.

Ya, same idea, but no mics involved. Everything from the input of the Helix to the line output of the amp, and all the FX Loop patch points in between. I'll check out that link though. Thanks.

If you're going to use the preamp in the second amp with different settings, wouldn't it make more sense to control their channel selection separately?

A question that I've seen asked quite a bit on this forum, and also one that I'd like to investigate further, is about levels when using 4CM. Back in the X3 days, when I really didn't know better, I used a plugin called Waves Q-Clone/Q-Capture to do some testing. This plugin's intended function is to allow a hardware equalizer to function as a plugin - basically it outputs a test tone to the input of the equalizer, analyzes the resulting output, and then creates a digital equalizer based on the frequency response it detects from the hardware equalizer. Basically you can theoretically own one good hardware EQ and apply that sound to more than one track. I don't own any good equalizers, so I never used it for that, but as it was capable of displaying the frequency response of a device, I used it to analyze what was going at various points between the input of my X3 and the output of my amp, at least in terms of frequency response and level. At the time, with my limited knowledge, it was more than enough, but I would like to do some more investigation and I'm thinking that there must be a better tool, one that is made specifically to test audio systems. So, can anybody point me to Windows-based audio testing program that works in a similar way but provides more information, more precisely? Something that outputs a test tone and then analyses it and displays the results. And maybe not just frequency response but also phase, distortion, etc.? Ultimately I would like to do my testing and then come back to the forum here with some potentially helpful information, not to provide a definitive answer (I'm not qualified to provide such a thing, and ultimately my equipment isn't "measurement grade" equipment anyway), but at least to provide some information that can provide a small bit of insight into the matter. Thanks in advance for any help.

Where's the *laughing hysterically* emoticon when you need it?

I agree. The Helix is a significant monetary investment and you're not going to get your money's worth by using that amp. Even your ME-80 is more powerful than your amp is capable of really doing justice. I'd upgrade your amp first. If you want to go fully down the modeling route, consider an FRFR like @HonestOpinion said, or a Powercab, which has built-in speaker modeling (different than cab/mic modeling) as well as being an FRFR. Once you have an appropriate amplification system, then you'll get more bang for your buck in buying a Helix.

Fair enough. Maybe the answer is "yes you can, but not without crippling a core functionality of the unit." That comes with a -6 dB gain reduction on both channels, which is easily enough solved with a volume block, but you're wasting a block, and as this is digital gain, those that are eternally worried about aliasing noise just won't be having it. I think the real answer is "the unit is not designed to function like that." There's a way to do it but not without a penalty somewhere. It's possible that the solution, actually, is to unplug one guitar, put it on the stand, pick the other guitar up and plug that one in, considering even a standalone A/B box apparently comes with its own issues as well (I've never owned one... I'll take @rd2rk's word on it). Some problems don't have a more elegant solution than a minor inconvenience.

Yes, it's possible, but I think the point that @rd2rk was making is that in order to make it happen, one needs to abandon a key functionality of the unit (I think more people use the second path than don't), at which point an investment in a standalone A/B box rewards you with another signal path in the Helix, which is a pretty good value from where I'm standing.