As one of the pivotal and most legendary innovators in sound since 1958, Universal Audio takes an uncompromising approach to crafting transcendent gear. This commitment is evident in the company’s UAFX modeling pedals that precisely emulate the tones, controls and quirks of iconic vintage amps, preamps, studio processors and effects.

The UA pedal team is diving deep once again, producing exquisite amp replicas of Peavey’s original 5150 (ANTI), MESA/Boogie Rectifier (Knuckles) and the mythic, rare and exceedingly costly boutique amplifiers handbuilt by Alexander Dumble (Enigmatic).

The main duo tasked with creating these pedals are self-acknowledged guitar-and-amp geeks James Santiago and Tore Mogensen. We’ve already talked with Santiago, UA’s Southern California-based senior product manager and sound designer (check out the interview here). But Mogensen isn’t exactly working right beside Santiago, nor does he park himself anywhere near the Universal Audio offices in Scotts Valley, California.

Instead, UA’s other senior product manager works remote, based a continent and an ocean away in Denmark.

Given the exacting circuit and sound modeling required by UAFX pedals, in this article, Mogensen explains how he and Santiago can successfully work thousands of miles apart, details how they decide on which amps and features to emulate, and reveals the inner details of ANTI, Enigmatic and Knuckles.

For a comprehensive look at all things UAFX pedals, please check out our Guide to Universal Audio UAFX Pedals.

Pictured: UAFX Senior Product Manager Tore Mogensen (Credit: Jes Vang)

How do you decide which amps should be emulated for UAFX Guitar Pedals?

Mogensen: When we started the project, James and I would always have this discussion: “If we were building an amp collection for a major studio and we wanted any type of guitar player to come in without an amplifier and get their tone, what amps would we need?” Ideally, anybody could come into that studio, and there would be something for every taste. You know, a player might say, “I want something that sounds like this.” And we’d say, “Well, we have an amp for that.” That was the concept for the pedals. Now, does that mean we’d have every single amp under the sun? No. But we’d probably have something that’s close, and we’d make sure the basic food groups were covered. The classics, so to speak.

But it’s not just the basic food groups. You go deep into specific vintage amps from those groups.

Well, we’re nerds for this stuff, you know, so we didn’t feel it was enough to just have an idea of a particular amp. Ideally, we try to do a shootout between five to seven versions of a vintage amp and grab the one we feel sounds the best. This is important, because there can be drastic differences between a lot of these amps due to wear and tear over the years, component value changes and all that stuff. It’s totally subjective, obviously, but we find the “golden model” for a vintage amp, and that’s what we emulate.

Even with the golden models at hand, it’s cool that you and James don’t typically try to “fix or correct” any idiosyncrasies in vintage circuits to clean them up for modern users.

Whenever we do any sort of gear emulation, we have this mantra: Do it warts and all. If there’s a weird artifact or anything quirky about the product, we model it. When we were working on the Knuckles ’92 Rev F Dual Rec pedal, for example, we noticed when you choose the red or orange channel, the presence control on the inactive channel is still active. Suddenly, the amp has two presence controls. I don’t think MESA/Boogie envisioned that as part of the amp’s features, but it’s there, so we decided to put it into the pedal. I mean, that’s part of how the real amp works and sounds, and it makes a pretty big difference to the sound depending on how you set the inactive presence control.

Part of the reason for our little mantra is that James and I are nerds, and it’s fun to discover this stuff. The other part, is whether a player knows about an idiosyncrasy in a circuit or not, that idiosyncrasy exists when they are dialing in their sound. So, we definitely want to make sure people can get the sound they expect when they plug into these pedals. In fact, one of the things that differentiates our amp pedals from a lot of others in the market is the fact they’re one pedal/one amp—the full feature set without compromise. People who really love a particular amp will see that our amp pedals have the same controls as the actual amps. When they set the controls in roughly the same positions they know from their real counterparts, they get a similar sound.

With the Lion pedal, however, while Plexi Marshalls are known for producing soft ghost notes between the notes that are played, you allow users to delete those artifacts if they so desire.

Yes. The app gives you the choice of taking out the ghost notes if you don’t want them. This was one of the times where something like ghost notes are so much a part of the circuit that we modeled it that way, but we also gave users the option of choosing those quirks or not.

Shop Now: Universal Audio UAFX Knuckles '92 Rev F Dual Rec Amplifier Effects Pedal

There are so many potential speaker cabinet options available for each amp that you model. How do you determine what to offer? Would you ever consider including something a bit unusual, such as a tweed Fender into a 4x12?

James and I know so much about the history of guitar that, to a certain degree, we are sort of guilty of going with the tried and true in terms of speaker combinations. We’re aware that plenty of things out there would sound great, but we wanted to model amp and speaker combinations that real-life users would typically use.

But you mentioned a tweed Fender into a 4x12, and I found out that sound is literally like the early Black Crowes albums. It’s an amazingly cool sound, and there are tons of examples, right? As speakers are such an underestimated but massive part of the overall guitar tone, you could argue it would be nice to have access to everything in every single pedal. But that direction also becomes with some option paralysis.

For the initial pedals, we went more in the direction of what we think sounds good. In the Knuckles pedal, for example, there’s a 4x12 British-style cabinet with Celestion 75s, because that’s what Meshuggah used on their seminal albums. However, we’ve been going a bit in the other direction with the Knuckles pedal by including a 2x12 Electro-Voice cabinet you wouldn’t associate with a Rectifier sound. We decided to highlight the really cool clean tones in a Rectifier by offering an EV option that rings out with a shimmery, super clean thing that we wouldn’t be able to get if all of the cabinets were 4x12 Celestion variations.

What about matching effects models to specific UAFX pedals?

We want to get the classic combinations in there, but we can’t do everything. When we did the Dream ’65 Reverb pedal, for example, we were like, “Oh, shoot. Should we add a Tube Screamer model so that people can get their Stevie Ray Vaughan thing going?” But, you know, a player can always put one in front of the pedal. That said, I must admit it would have been quite nice to have a KORG SDD-3000 emulation available in the Ruby ’63 Top Boost pedal to make it easier to get close to The Edge’s delay sound.

But there are literally pages of things we would love to do, if it was possible to do them all. At one point during the Enigmatic process, we talked about adding a Klon in there—just to make that pedal an emulation of the most expensive rig of all time.

What is the process for getting all the development and production done across the great divide? Do you have all the amps with you in Denmark and track progress via Zoom meetings with the California team?

It is a bit of a logistical nightmare, to be honest. We started this whole pedal endeavor shortly after I joined the company in late 2018, and it wasn’t long thereafter that COVID hit. So, working remote was something we were all doing at the time. Every single person on the guitar team worked from home. It was challenging, but being in Denmark didn’t feel much different from James working in Los Angeles—500 miles away from Universal Audio’s main office in Scotts Valley. Even those people were isolated in their offices and couldn’t see each other.

From the pandemic to more recently, it has been a lot of meetings at all crazy hours of the day and shipping amps, pedals and prototypes around. In many cases, we had to buy additional versions of the amps. For Lion, both James and I own Plexis, so that made things a little easier. We’re guitar nerds, so we also own a lot of the other amps we did pedals for. I used to think I had way too much gear, but when I met James, I was like, “Wow, I’m not even scratching the surface. I think I can buy lots more gear and still feel pretty good about it.”

For the Enigmatic pedal, however, neither James nor I had Dumble Overdrive Specials sitting around. But Los Angeles is a nice place to be if you want to listen to Dumble amps. It would have been a nightmare for me to try to find one here. So, James was sort of the main guy for that one. He did the heavy lifting on the tone tweaking. On the other stuff, we tag team a bit more.

Do you take on certain aspects of a project such as Enigmatic, while James deals with others, or is it more like everybody is free to do everything?

Our collaboration is not entirely split up, but there are defined roles. As the product manager, my job is overseeing the business of pedals—figuring out what we are going to do today, tomorrow, next year, five years from now and beyond. Then, it goes down to individual projects in terms of roughly establishing what they should do, what the feature sets should be and working with the engineering team. This is where James starts coming in heavily, because as the product designer, he’s way more focused on the sound of the product. At the end of the day, it all sort of blends together, because it’s not like either of us has the final say with any of this stuff.

Do you and James complete a listening session and then take a vote on which amp sounds like “the one”?

We don’t do a vote. Typically, we agree on pretty much everything. Honestly, I trust James a lot on the vintage stuff, because that’s his bag. When it comes to the hard rock stuff, I’m usually more in the driver’s seat, because that’s what I grew up on.

However, you and James aren’t usually sitting in the same room listening to amps together. So, what language do you use to ensure the other can interpret precisely what each of you is independently hearing?

It’s super tricky to be honest. When we do these things, we prefer to meet up in the same place at least a couple of times during the process. We might not agree on something because we’re hearing different things, or the QA (quality assurance) team is saying, “We hear this weird rattling thing.” If we’re all together, we can say, “Yeah, that rattling is how the amp sounds—that is literally what it does,” as well as work out any questions between James and me.

As far as developing a kind of “tone language,” pretty much all of the amps we’ve done so far are ingrained into the subconscious of guitar players. The benefit there is that we know what we’re listening for, because we’ve all played them in real life. If we’re talking about the Lion pedal, for example, James and I have played through enough Plexi Marshalls over the years that we have a common language based around how those amps should sound. It’s really no different for other guitar players who love Marshall amps. On the other hand, Enigmatic was tricky because I had never played a Dumble before we started the project. I wasn’t as savvy about knowing what to listen for—when it sounded right and when it didn’t sound right—or how to best describe the amp’s nuances and subtleties.

Well, it must have been extraordinary to plug into your first Dumble.

Man, it’s crazy. A Dumble is almost like a mythical creature. Fortunately, there were some people—who I can’t divulge—that were gracious in giving us access to their amps for a period of time. It’s not like you go and buy one, right? That amp has created some of my favorite guitar tones of all time, so it was a unique and fun experience to be able to play through one.

Can you describe the experience?

It was interesting. The Dumble clones and preamp pedals I’ve tried were much more polite sounding than the real deal I played. But that’s the thing with Dumbles, right? Every single one is different. So, I can’t say if there are other Dumbles that sound more like the “inspired by” versions I’ve tried. However, the actual Dumble amp I played was—I don’t want to say unruly, because it wasn’t, but it was definitely raw and alive. It just lives and breathes in a different way.

Shop Now: Universal Audio UAFX Enigmatic '82 Overdrive Special Amp Effects Pedal

Given that Dumbles are extremely rare, fabulously expensive and very few people have actually played one, how do you work with reviewers who are kind of winging their evaluations of the Enigmatic pedal? We assume most reviewers—and players—do not have any direct experience with a Dumble, or how to compare the amp to the pedal.

It’s interesting to see the people who really did their homework regarding Dumble lore and those who go, “I’m just going to play this—even though I’ve never experienced an actual Dumble.” Both approaches are totally fine. But for all of those players and reviewers who never tried one, we’ve tried to offer manuals and a flowchart detailing the variations and options in the app. After all, a Dumble is probably the most versatile amp in existence. It can sound a million different ways. It has definitely been more time-consuming for James and me to guide people through the pedal. I’ve literally spent hours on the phone with a couple of reviewers—and so has James—to make sure they understand what the different components do, and why one era of the amp is different from another era.

There’s a lot of information to share, because while I don’t feel someone can necessarily make the Enigmatic pedal sound bad, it’s very easy to find tones that aren’t for you. This doesn’t mean there isn’t a sound in there that’s right for you, but it may take some study. Obviously, anyone who buys this pedal doesn’t have the luxury of having a Dumble expert tune it for you while you’re playing and ask what you think. You have to do that yourself—hopefully, with the help of the manual, the flowchart and your ears.

Finally, there’s the app. I can’t take any credit here, but James did an absolutely stellar job making a whole slew of presets that highlight all the different things those amps can do. If you scroll through the presets, you will get a pretty good idea of the different variations of the amps, what they can do for you and how to find your own sound.

Considering the roster of famous Dumble users, such as Robben Ford, John Mayer, Carlos Santana, Larry Carlton, Stevie Ray Vaughan and Henry Kaiser, why didn’t you associate specific presets with iconic guitarists?

We very deliberately decided not to call any of the presets something like a “famous player X sound.” We felt it was more important to offer tonal options, such as a “super clean, incredibly high-headroom, never-breaks-up type of sound.” We provide a nice starting point, but you still have to set the tone controls and tweak the sound to your liking. Of course, if you’re into that tone, you might already know a couple of famous artists who used that sound themselves. But we didn’t want to focus on players. We decided to showcase the Dumble’s different sounds, because we want players to find their own voice with Enigmatic.

For the ANTI pedal, you’re dealing with a relatively modern, production-line Peavey 5150. How is that development different than modeling a vintage amp from the ’60s?

In the case of the 5150, it’s a little easier to get a great-sounding unit because you don’t necessarily have to go out and buy a specific one—even though we do. Honestly, there’s a very slight difference between an early 5150 and a later model. That said, the early block letter amps are the most coveted. But even then, if you find three different block letter 5150s, they are going to sound the same—assuming they’ve been well maintained and have the same tubes and so on. With the vintage stuff, a big part is tracking down really great-sounding examples.

How do you, James and the UA team typically determine when a pedal is ready to release?

I can’t think of a single instance where we felt like we needed more time on the core sound of a pedal. Typically, the software algorithm starts way before everything else, so it’s rare that we run out of time and have to say, “It sounds good enough.” It’s more that we discover where we need to shift things. In the instance of the Dream ’65 Reverb, for example, the amplifier algorithm is large and complex by itself, and the spring reverb in the pedal is also super large and complex. So, we were like, “Well, it’s not a Deluxe Reverb unless there’s a reverb in there, and we have a great-sounding spring reverb that is just like the real thing. I guess we’ll have to postpone the project until we solve this.” We don’t skimp on sound quality. If we must, we’ll typically skimp on other features, such as adding MIDI or putting that KORG SDD-3000 into Ruby.

When you do a project like this, you always have a very long laundry list of things you want to do. But we know we’re not going to be able to make every single one of them happen, because then the project will never get finished. We sort of put the important stuff on top of the list, and the least important features near the bottom. The goal is to ensure that anything we decide to remove from the list is not essential to the final product.

Shop Now: Universal Audio UAFX Anti 1992 High Gain Amp Effect Pedal

As firmware updates are available for UAFX pedals, you can address anything that might have been missed on initial release. Do reviews and user feedback inform software revisions?

Sometimes. A reviewer or a user might go, “This is cool, but it’s not great.” We’ll make a note of it, and if we agree, we’ll try to improve it. As an example, we thought we put a decent noise gate into the ANTI 1992 High Gain Amp pedal, because a gate is pretty crucial for metal. But we got some feedback from users that the gate had some chatter we could improve, so we did a software update.

Can you describe how the noise gate was modified?

Basically, the original version of the noise gate algorithm had one threshold level that applied to the closing down and the opening up of the gate. That was fine for metal chugging, but if you held a note, it would get a little bit chopped at the end. We found out what you really want is for the gate to open as soon as you do something. You don’t want it to open slightly, and you want it to open very fast. At the same time, you want the gate to close very slowly up until the point where there’s nothing to hear. So, we added a second threshold—one for opening the gate and one for closing it—and that makes a big difference in terms of how it behaves.

How do you use UAFX pedals for your own gigs and sessions?

There’s still something magical about the real things. I’d never sell the amps I love. But as somebody who does quite a bit of gigging and recording, who also lives in an apartment building, there’s a convenience factor to the pedals that’s hard to beat. I can record absolutely amazing-sounding guitars without having to mic anything or worry about the noise. I just know the tone is there and it’s consistent every time. The same applies to playing live. Every time I bring one of the pedals, sound people love me. I’m not cranking up my Super Reverb because it sounds great with the volume at 6. The audience, the sound crew and my bandmates are not going to be super happy when I do that.

Also, I always bring an equivalent pedal of the amp I play. For example, if I’m bringing my tweed Fender to a gig, I take a Woodrow pedal with me. If the tweed dies, I don’t have to play through some random amp that the venue scrambles to find. I can simply plug into my Woodrow and get my sound.

With so many modeling processors and multieffects available at various prices, what do you feel is the major benefit of relatively expensive, single-amp UAFX pedals?

I’m not knocking the cheaper amp solutions out there, but I would argue that our $400 pedals sound stunningly close to real, super expensive pieces of vintage gear that have been used on countless albums.