zappazapper

No, not at all. Sounds like this is all pretty new stuff to you, but you're getting it pretty quick. This is correct. Everything is sequential. Think of the horizontal white lines between blocks the same way you think of 1/4" cables between pedals, and think of your Mesa preamp in the loop as just another pedal. If you want your signal to go through a compressor and a boost before it goes into your preamp, then obviously they need to be before the loop in your signal chain, which runs left to right. So we have: 1 - compressor 2 - boost 3 - preamp model 4 - FX Loop Left, which sends the signal to the Mesa preamp via the front panel input and then receives the output of the preamp coming from the amp's FX send, via the Stomp FX Return Left. This is confusing me a bit. I want to make sure that I understand what you're saying here. Can you tell me what the FX Loop Right block does?

K, you're getting a lot wrong here. Let's just start at the beginning. Think about this for a second. You said you want a compressor and a boost feeding your Mesa preamp. So why would the first block be FX Loop Left? What do you think the correct order is?

No. In 4CM if you have an empty preset your guitar signal will be running straight into the power amp, because your 1/4" output should be connected to the FX Return of your amp, which is a direct patch into your power amp. The only way you can patch it into the preamp and back to the Stomp is by adding a Loop block, in your case Loop Left, assuming the loop left send is connected to the front panel input of your amp and the FX send of your amp is connected to the loop return left of the Helix. The easiest way to test this is to load up an empty preset, and see if the gain and tone controls on your preamp do anything - unless you have the Loop block in place, they shouldn't do anything, and if they do, then you don't have things connected properly.

You have a chorus and a delay pedal in FX Loop Right, don't you?

Yes. The only thing unusual about this is the chorus and the delay pedal being BEFORE the amp model. It's not wrong, just not "conventional". Most players put modulation and delay AFTER their amp block, but putting them before the amp might create an interesting sound, so feel free to experiment. Well, you said you wanted the Fender amp into your Mesa preamp, so you would do the Preamp block first THEN the FX Loop Left. But other than that, I think you're getting it. Ya, don't do that. 4CM is a little weird, and you shouldn't be discouraged just because it doesn't work perfectly after one day. You can search on this forum for my username and see that after almost 15 years of using 4CM, I'm still not sure I'm doing it right. But it sounds as though you have the basic idea figured out, and I'm sure you can tweak it to your own unique situation the more you experiment with it. Glad I could help.

You're right, what you want is a Loop block, not a Send block. Loop blocks are created from the same Send/Return block category as Send blocks, in the Mono subcategory. And you should be able to change your existing Send block to a Loop block by highlighting it and selecting a different model from the same category/subcategory.

It's not my favorite thing about the Helix, but it's hardly the first thing I would change/improve. I do find them to be unnecessarily long, and I find the knobs themselves to have such a fine ratio as to be frustrating to use. But again, I can think of 19 other things I would change before this.

No problem at all. If you've never done it before, 4CM can be a little confusing at first. This is basically where the confusion comes from. It's true that effects loops on amps were first intended to give the user a way to put effects "between the preamp and the power amp", but with 4CM it's best to think of the effects loop on the amp as patch points to separate the preamp section from the power amp section - the effects send outputs a line level signal from your preamp, and the effects return is a direct line level input into the power amp. Let's pretend for a second that you have no plans to use your amp's preamp; you're only interested in using the amp models. Because amp models come with their own distortion and tone stack, it doesn't make sense to run the output of an amp model into the front panel of an amplifier with its own tonal characteristics. If you want a more accurate representation of an amp you're modeling, it's best to bypass the preamp of your amp entirely and connect the output of the multi-fx directly to the power amp, via the FX Return on the amp. And when amp modeling first came out, before multi-fx units had FX loops of their own, this is often how people used modeling processors with traditional guitar amps. Guitar > multi-fx input, multi-fx output > Amp FX Return. When multi-fx units started coming with their own FX loops, it then became possible to insert the preamp of a traditional guitar amp into the multi-fx unit's FX Loop - and that is really the best way to think about 4CM - you're putting the preamp of the amp into the FX Loop of the multi-fx. You're not putting anything "into the loop" of the amp, you're just using the amp's loop for its patch points. So then 4CM becomes: Guitar > multi-fx input Multi-fx FX send > Guitar amp front panel input Guitar amp FX send (preamp output) > multi-fx FX Return Multi-fx Output > Guitar amp FX Return (power amp direct input) And so what this does is allow you to still run amp models directly into the power amp of your guitar amp, or instead of using an amp model, you can use the preamp in the FX Loop of the multi-fx in its place. And when you're using the preamp in the loop, it also allows you to place certain effects like distortions, wah pedals, and certain compressors BEFORE the preamp in the signal chain, and other effects like modulations, delays, reverbs and other types of compressors AFTER the preamp, because the preamp of your amp becomes just another block that you can place anywhere you want in the chain. Of course, there are no rules about where effects should go in a signal chain, nor are there rules about running an amp model into a real amp's preamp, or vice versa, but at least with 4CM you have separated all these elements out on their own so that you can use the things you want, where you want in the signal chain, and leave out the things you don't. A note about Mesa Boogie amps - many of them have parallel FX loops. I don't have first hand experience with these types of loops (my .50 Caliber Plus has a serial loop), but the issue with these loops seems to be that a 100% wet setting (which is what you want if you're using 4CM) doesn't completely mute out the dry signal coming from the preamp. I imagine that this can manifest itself in a variety of undesirable ways, but as I said, I have no experience with this issue myself. Maybe somebody that has more experience with parallel loops can chime in and give you advice on the matter, if you are indeed dealing with a parallel effects loop.

Ya, I'm still not sure you got it right. First of all, a Send and a Loop are not the same thing. Both send the signal out, but only a Loop brings it back in. There are very few applications for a Send block in 4CM, and I can't even think of one off the top of my head. Maybe some weird parallel routing schemes? Second, the purpose of 4CM is to allow you to use the preamp of your amp IN PLACE of an amp model, while as far as I can tell, you're trying to use both. There are no rules that say you can't do this and get a good tone, but the way most players use 4CM is to use either the amp's preamp in the loop OR an amp or preamp model. Also, you're right about probably not needing any of your pedals. Unless it's something the Helix just doesn't do at all, like a specific synth pedal or something, you'll probably be able to find something that works just as good or better than your pedals, not to mention that if you use the stuff internal to the Helix, you can now control everything about those effects, instead of being stuck with one setting or having to bend over and twist knobs while you're playing. Not to mention that if you're not plugging your guitar into the Guitar Input of the Helix, you can't make use of the variable input impedance feature of the Helix, which can be critical to accurate modeling of amps and effects.

You still haven't answered Phil's question. The physical connections are one thing, which you seem to have right for your desired setup, but you also have to have the right loop blocks in the right place in your preset for it to work. To me that sounds like you don't have the loop block in your preset that would send the signal to the front panel of your amp and then back to the Stomp from the FX send of your amp.

Just something you might want to check. Years ago I had a Fender '65 Reissue Twin Reverb that had a Normal and a Vibrato channel, but they weren't switchable, they had separate inputs. I had found out somewhere that Fender preamps generally have a built-in mid scoop that can be cancelled out by setting the Treble and Bass controls at 0 and the Mid control at 10, so in the absence of an FX Loop, I figured this would be the best way to use the amp modeling of my X3 Live, but I still wanted to be able to use the natural sound of the amp sometimes, so I connected the Left 1/4" output of the X3L to the Normal channel with the Treble and Bass controls at 0 and the Mid at 10, and the Right 1/4" output of the X3L to the Vibrato channel. The plan was that if I wanted to use amp models, I would pan the signal to the left in the Output settings, and if I wanted to use the Vibrato channel of the Twin, I would pan the signal to the right. But what I found out was that there was crosstalk between the 1/4" outputs - if I had a signal panned to the left, there would still be a tiny bit of signal coming out of the right output, and vice versa, and depending on what I was trying to do, it would often be enough to make it impossible to get the tone I was after, because there'd be a bunch of high frequency fizz coming from the other channel. So it might be a good idea to check and see if there's any crosstalk between the 1/4" outputs of the Helix before trying your suggested setup. I no longer have that Twin, I have an amp with an FX Loop which I run in 4CM so I'm no longer trying to run things in that way anymore so even if there is crosstalk between the outputs, it's not an issue for me anymore, but it might be an issue for you.

Fair enough. @FAchterberg it seems that S1 has issues with MIDI. Unless you're dead set on using it, I would also recommend Reaper.

Like @phil_m said, you have to be in Stomp Mode. You set your Bypass and Controller Assign switches the way you always do, but if you want a Snapshot or a Preset assigned to a switch, you use Command Center.

@rd2rk he's trying to send MIDI to the Helix to change Snapshots, not record MIDI from the Helix. But perhaps if you had issues with Studio One and MIDI in general, that might be the first place to look at. @FAchterberg do you have any other DAWs you can use to test, just to remove S1 from the equation? You can download the full version of Reaper for free.

So this is the video I was talking about: I'm pretty sure I understand what the Bias parameter does. Basically one side is Class AB and the other Class A, with varying degrees of crossover distortion. It seems to me rather impossible to simulate Class A behavior with a power amp that almost certainly will behave like a Class AB amp (because my amp IS Class AB), and probably more likely that you could simulate Class AB behavior with a Class A amplifier. Like, if it were that easy to make a Class AB amp without crossover distortion, somebody would be very rich, I think. I'm not sure I understand what Bias X is doing. I understand that it stands for Bias Excursion, but I don't know what that means.

I've been thinking about this a lot. Hear me out. A real-world analogy, because it's all I got - when my air conditioner turns on, my lights go dim for a split second as my air conditioner also struggles to ramp up to full power. My light bulbs don't draw a significant amount of power, but the effect on them is noticeable all the same. Is it possible that the effect of sag on the preamp is being understated here? Is it possible that when L6 was testing amps, they noticed that sag caused by the power amp was also affecting the preamp? Is it possible that when they decided to include Preamp models, they considered that the target audience for Preamp models is either 4CM users or those who use standalone tube power amps; basically anyone who's using a power amp that would not only experience its own sag but also cause sag in a preamp if one existed and was being powered by the same power supply? Is it possible that L6 figured that, in the interest of accuracy, they had better include a Sag parameter in their Preamp models that simulates the phenomenon as it occurs in a preamp sharing a power supply with a power amp being hit hard? I have had many very interesting discussion with the people on this forum and have learned SO MUCH from those discussions, but I'm having a hard time accepting that the Sag parameter in the Preamp models is just a mistake. I'm hoping someone can chime in here and help me understand why a preamp isn't the same as my light bulbs.

I promised myself I wouldn't harass the forum with another bump until it hit 30 upvotes. BUMP!!

He's got a weird rig, like a wet/dry thing. He uses a Chorus Ensemble as a splitter. One side goes to an overdrive then an AC-30, the other to his Demeter preamp then to a digital reverb that again splits the signal to a stereo rack power amp, and off to Marshall 4x12s on either side of the Vox. According to the article, the Vox is always on, because he likes how it adds clarity to his rack rig. That might be a good place to start as far as nailing the basic tone, although I don't know what you substitute for the Demeter. The "70s Chorus" Helix model is a model of the Chorus Ensemble, so another good place to start. I don't know if you're running a stereo rig, or if you need to, but you might want to try doing what he's doing, use a stereo chorus and send one side to an AC-30 model and the other side to something more conventional, like an 800 or something. It seems to me that the Demeter is that kind of amp. Marshally. Could be wrong on that. Maybe someone will chime in.

So, it's just a mistake then? That seems hard to believe. They must think it has enough of an effect to put it there. I'll have to check tonight and see what it does when it's a preamp vs a full amp. Weird.

So if is rectifying power for both the power amp and the preamp, then sag also affects the preamp, and theoretically when using a Preamp model, the Sag control will emulate only those phenomenon that exist in a preamp, and when using a full Amp, it would emulate the phenomena that exist in both sections of an amp?

I was thinking about doing something where I record a guitar track in Reaper direct, reamping it through my Helix in 4CM with my amp, recording the direct out, recording one pass with a preamp model and another with the same full amp model, flipping the polarity on one and comparing the difference. Like, try to find which settings null out as much as possible, and maybe that's as close of a representation of what the power amp in my own amp is doing, in the same terms as the Helix parameters. But there's a lot of variables there. I would have to select an amp model that had a power amp that is similar to my amp, and I don't really know enough about power amps to know which one that would be. The .50 Cal is essentially a poor man's Mark III but what's essentially different between it and a Mark series amp is the straight Class A/B power amp instead of the Simul-Class thing. So I don't know how useful that kind of approach would be.

https://www.aikenamps.com/index.php/what-is-sag I'm not suggesting that Aiken Amps is a particularly credible source of information, but it was the first thing that popped up when I googled "tube sag". It mentions rectifiers, transformers, and filter caps. I know the transformer is part of the power amp, but what about rectifiers and filter caps?

That is essentially what an impulse response is, isn't it?

Is it possible that both preamp tubes and power amp tubes experience sag, and that the preamp models are modeling only preamp sag and full models are modeling both?

Well, I think it's part of the same conversation. I mean, I get that it's entirely possible to get useful tones by doing things that are completely wrong from a technical point of view, but let's not forget that Helix is a modeling processor, with the supposed goal of accurate representation of the amps being modeled. IIRC, you were part of the discussion I started about impedance of the loops and why my amp sounded "screamy" in 4CM. If I hadn't had that discussion, I would have never figured out that the issue was actually that by placing a buffered device between my guitar and my amp, I wasn't loading my pickups in the same way. In that case, "how does it sound" was being affected by a technical issue that I didn't properly understand, and now that I do, it sounds exactly like it does when I plug straight into the amp. Y'know, I saw a YouTube video the other day where someone was measuring the effect of the Bias and Bias X controls on an oscilloscope and I think it may have been him. And I didn't put two and two together, but that's the guy that's always on about the 5150 III, IIRC. Thanks for the tip. I'll check out his stuff and maybe contact him with some questions.