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Universal Audio UAFX Amp Pedals

UAFX Guitar Amp Emulator pedals

In a world where makers of digital amp simulators take pride in offering a huge variety of models, Universal Audio have adopted a ‘less is more’ approach.

Almost exactly a year after Universal Audio launched their UAFX pedals, it’s finally here. Or rather they are here. For what we have are the first three in what must surely be intended as an expanding series of model‑specific virtual guitar amps. Housed in the same aluminium chassis as the UAFX units and with the same physical layout of controls, there’s a modelled 1955 wide‑panel Fender Deluxe, a 1961/1963 Vox AC30 and a 1965 Deluxe Reverb, or, to give them their full names, the Woodrow ’55 Instrument Amplifier, Ruby ’63 Top Boost Amplifier and Dream ’65 Reverb‑Amp. “What, no Marshall?” you might be thinking. Me, too. Surely next?

In a recording context, at least, you might question the point of hardware boxes at all, given that you can access very high‑quality amp emulations in software, not least in the UA ecosystem, with minimal latency. They already have a highly regarded ’55 Deluxe as a plug‑in, but this one, whilst using the same algorithm, models a different actual ’55 Deluxe. Personally, I prefer my amp emulations to come in a hardware box with physical controls, preferably the same as the ones on the real amp, to which I can directly connect a guitar and know that input level and impedance are not variables. In contrast to any other hardware amp‑simulator platform I can think of, however, each of the new UA pedals models just a single amplifier type. There’s no MIDI or external control, no effects loop and no headphone output, and there are no effects other than a room or spring reverb emulation and whatever tremolo the original amp would have... and they cost about the same as a Strymon Iridium, which will give you three classic amps, or an Atomic Ampli‑Firebox MKII, Boss IR‑200 or Line 6 Pod Go that will give you loads. They’d better sound really, really good then!

OX‑style Dynamic Speaker Modelling

Each virtual amp is paired with one of three user‑selectable, UA OX‑style dynamically modelled speaker, cabinet and miking combinations. An additional three ‘bonus cabs’ are available on registration of the pedal via the UAFX app (the whole ‘cab, mic and room’ element can also be bypassed for running the pedal into a real guitar amp), and there are three custom boosts or circuit mods you can select. The speakers and boosts are all unique to each amplifier, reflecting both standard equipment and historically favoured alternate choices.

Like the UA effects units, the pedals run in one of two modes: Live or Preset. In the former, everything is as per the controls’ actual settings, while the latter recalls a pre‑saved setup, including the master output level. You can save a preset directly using a switch on the pedal itself, but otherwise they are managed by a Bluetooth‑connected mobile app, available for both iOS and Android. The app will allow you to backup and restore your preset library, access the factory and ‘artist’ presets, and reassign the functions of the two footswitches. A USB‑C port is presently reserved for registration and firmware updates, but I’m sure primarily studio‑based users would like to see the mobile app functions implemented in a wired‑connection desktop app, too.

External 9V DC power is required, using a standard 2.1mm centre‑negative pedal connector. Note that a suitable power supply is not included with the pedals, and that not all pedalboard power supply outputs may have the required 400mA current capacity.

All pedals have two inputs and outputs (which can be used in different configurations), a USB‑C port for firmware updates, and Bluetooth for communicating with the app.All pedals have two inputs and outputs (which can be used in different configurations), a USB‑C port for firmware updates, and Bluetooth for communicating with the app.Audio connectivity consists of four unbalanced jacks (two in, two out). One input and one output will give you the sound of just one amp instance. There is a true stereo path through the unit if you use both inputs, but if you use one input and both outputs, you are actually running two phase‑locked instances of very slightly different amps, as if using an A/B‑Y box. Huge in mono, and some subtle spread in stereo. The ’55 Deluxe and the Vox amps feature the ‘very real’ Dynamic Room Modelling used by UA’s OX processor, while the ’65 Deluxe has a modelled spring reverb, or in fact two, if you use both outputs, as each amp has one, resulting in a bit of spread due to the slight differences.

There’s an interesting reconfiguration of the ins and outs available within the app in the form of ‘4‑cable mode’, designed for use with amps that have an effects loop. Once enabled in the app, you can connect output 1 to the front of the amp, where you would normally connect a guitar, and output 2 to the amp’s effects‑loop return. The loop send is then connected to input 2 on the UA pedal. Now, with the pedal bypassed, your guitar signal goes straight into the front of amp, with the pedal’s input 2 routing straight across to output 2 to complete the effects loop. Any processing that you would normally use in the loop gets patched in between output 2 on the pedal and the amp’s effects return. When you activate the pedal, the guitar signal bypasses and replaces the amp’s own preamp, entering at the loop‑return stage, whilst the effects loop continues to function as normal. There’s enough output level on tap to match or exceed the output of the internal preamp on anything that I tested. Clever, but also potentially accident‑prone enough to have the app asking you confirm, alongside a ‘Feedback Possible’ warning.

Preset Handling

Universal Audio UAFX Amp Pedals

The app caters for configuration and preset management, but it’s probably fair to say there’s scope for this to be developed further.The app caters for configuration and preset management, but it’s probably fair to say there’s scope for this to be developed further.By default, the two footswitches select Live and Preset mode (versus buffered Bypass), but you can assign the right‑hand one to be perhaps a Live/Preset toggle, while the left toggles something useful like boost, reverb or vibrato. A caveat here is that the footswitch modes are remembered by the pedal, so if you assign both switches to something other than Live/Preset selection, you won’t be able to change mode without then using app to reassign one of them. Given the potential vagaries of Bluetooth connection and the possibility of your mobile device being inconveniently out of power, I think there really should be an emergency ‘revert to Live/Preset’ routine accessible by rebooting while holding down both footswitches, or something.

You can backup all your presets (User, Factory and Artist) to the app as a single batch file, but you can only have one backup at a time, so a subsequent backup will overwrite the previous one. All the presets actually reside in the pedal, but without the app, you can only access the most recently active one. Any presets not stored as part of the backup batch file will be overwritten when you execute a Restore, unless you choose Merge instead, in which case you can end up with duplicates, as presets with the same name are not overwritten. Hmmm.

There’s no way to examine the settings used by the presets, which is disappointing as there are things to be learned from them. A graphical representation of the control positions in the app would be enough. Some presets also use setups not available in Live mode (mismatched speaker pairings, off‑axis miking) which I find rather frustrating. The controls obviously don’t represent the active values when you recall a preset, and as soon as you move one it becomes active at its new value. You can match a preset by ear, to some extent, and there is a small text description for each preset available in the app that details a couple of major parameters.

Clearly, with no MIDI and no preset selection from the pedal, the design goal looks like it was “make an amp sim that works with the immediacy and simplicity of a stompbox”. And it certainly hits that mark, especially if you just treat it like a two‑channel amp, with perhaps a clean sound in the Live setting and a more driven one as a preset, or two versions of the same setup, just with a volume difference (the output level is part of the preset).

California Dreamin’

Whilst I find the app somewhat undercooked, I am pleased to report that the pedals themselves sound spectacularly good! I’m going to start with the ’65 Deluxe, because that is my amp of choice in the real world of actual tube amps — mine is a ’68, but tweaked to the earlier spec, and also with some of the same mods. If starting from scratch rather than using a preset, you’d first choose your amp style: Stock, Lead (a Dumble‑style mod) or D‑Tex (a César Díaz‑style tweak up, as done for Stevie Ray Vaughan’s amps). The latter pair both involve some altered gain‑staging and revoicing to achieve a smoother overdrive tone. You can then choose your speaker, cabinet and mic setup. These are combinations that are ‘pre‑optimised’: you can’t mix and match speakers with mics, or alter their positioning, or relative balance. They are what they are. Although initially concerned, I found I soon ceased to think about it at all, because if you fundamentally don’t like the speaker sound it’s so easy to just move on to another one and see if it is better.

The Dream ’65 Reverb‑Amp models the classic Fender Deluxe... and it does so very nicely!The Dream ’65 Reverb‑Amp models the classic Fender Deluxe... and it does so very nicely!I haven’t yet failed to find one that worked for any particular amp settings I’ve dialled up. Some that initially seemed a bit bright in isolation were perfect once I put them in a track. The ’65 Deluxe offers a choice of a Celestion Greenback 25, a period‑correct Oxford speaker, and an EVM12. If you’ve registered the product with Universal Audio and downloaded the bonus cabs, you’ll also have a ‘boutique 2x12 ported cabinet’, a 4x10 combo cab, and a 2x12 with JBLs. Mics are drawn from a selection of Shure SM57 dynamic, Royer R‑121 and Beyer M160 ribbons, and an AKG C414 capacitor model.

The single volume control behaves like the one on the Vib channel of the real thing, complete with the hardwired ‘bright’ capacitor across it. The Lead‑mod option ditches the bright cap when the Boost control is anywhere above Off, and it would have been good to have some way of ditching it on the stock setup, too. Many users prefer the amp without, although there are admittedly some classic Deluxe clean sounds that rely on it for a bit of sparkle. Like all volume‑control‑bypass bright caps, this one gradually diminishes as you advance the volume, and anywhere in the upper quarter it is no longer an issue.

DI’d into a recording setup, and driven by typical single‑coil or humbucking passive pickups, the Stock modelled Deluxe displays a typically 6V6‑tube ‘sweet’ style of clean up to about four on the dial and gradually begins to offer up a very touch‑sensitive, edge‑of‑distortion break‑up thereafter. And if you’ve selected the stock Oxford speaker, too, you’ll begin to hear why they are colloquially referred to as ‘Oxfarts’. Very realistically modelled here, and the very reason why mine now resides in a box in the attic.

Favourite Fender Mods

The classic tone control setup for a ’60s Deluxe tends to be around treble at six, with bass at three, and that works just the same for the modelled stock amp here. When you start using the modified amps, I find those settings seem to want to be more like seven and two, which mirrors my real‑world experience. The modelled tone stack obviously works in conjunction with the circuit tweaks of the modded amps.

The D‑Tex mod replicates the effect of completely disconnecting the vibrato circuitry, adding both lower midrange and gain, as well as progressively bypassing the tone stack, for even more gain as you turn up the Boost. I have this mod in my Deluxe, too, and it is super‑well replicated here, complete with the potential pitfall of making things too ‘woofy’ if you are not careful to balance its effect against other control settings.

The ‘Dumble‑style’ boost is also a progressive tone‑stack lift, but compensated for to some extent in later circuitry. You can safely use more of it to sound like Robben and Larry in their ‘D‑style’ period. In stock mode, Boost provides just a clean boost into the front of the amp, up to 10dB of it, and is audibly different to just turning up the volume, as you’d expect in the real tube‑amp world. Even on the highest‑gain sounds, amplifier self‑noise remains low — much lower than the real thing. That’s one area where I’m very happy to see modelling departing from ‘accuracy’!

Then there’s the reverb, or two of them if you are using both outputs. There’s just a single control, as in the real thing, but nothing you’d want to tweak: just beautiful for anywhere between subtle and surf. And finally, the so‑called Vibrato effect (really Fender’s period‑correct optical Tremolo circuit), accessed by selecting the Alt position for the centre three‑way mini switch, which re‑purposes the Treble and Boost controls as tremolo Speed and Intensity, respectively. If you like the deep throb or repetitive warble of an optical trem, you’ll be happy with this one.

When you return the centre switch to the Amp position after setting trem parameters, you retain the sound as if the Treble and Boost controls hadn’t been adjusted, but they will now be in the positions in which you achieved your desired trem setting. As soon as you move one, its sound will jump to the new position. It’s not ideal, but there are few enough controls that it’s not really a problem in practice. I guess it is just the sort of compromise you have to make in trying to implement as much operational facility as possible into a small number of physical controls.

UA’s Dream ’65 Reverb‑Amp is capable of some of the finest, most detailed and, above all, most playable emulations of a recorded amp sound I’ve ever heard. There’s proper tube‑rectifier ‘sag’ like I have never felt before in a modeller. The guitar’s controls behave properly, and the clean tones have real life and sparkle like they should, not the ‘generic clean tone’ that some modellers seem to resort to when there’s no obvious distortion component. If you can’t find anything in there that makes you very happy, maybe you just don’t like Fender amps.

Ruby, Ruby, When Will You Be Mine?

If the Dream ’65 is a single amp with a couple of mod options, the Ruby ’63 Top Boost Amplifier is two different Vox designs: a ’61 pre‑Top Boost model, and the Brilliant and Vibrato channels of a 1964 Top Boost example, although both with the same quartet of EL84s for an output stage. Quite different‑sounding, but each very nice in their own way, the ’61 (called Normal here) replicates just about the simplest circuitry you can have in a tube guitar amp. With no tone stack and therefore no need for a makeup gain stage, there are just Volume and Cut controls, the latter implementing a treble roll‑off. Users of the real thing will know the very narrow range in which the Cut control is useful, and appreciate it being spread out more sensibly across the pot, whilst keeping the same overall range. Modelled speaker options are 2x12 configurations of vintage 15W Celestion Silver Bulldogs, Alnico Blues, or modern G12Anniversary models, with the ‘bonus cabs’ offering a modern rendition of the Alnico Blues, modern ‘Matchless’‑amp‑style speakers, or a modern Celestion Alnico Gold in a 1x12 cab. Each is pre‑assigned a mic type, drawn from Sennheiser 421, Shure SM57 and Beyer 160 ribbon.

Universal Audio UAFX Amp Pedals

This channel doesn’t have the gain of the Brilliant channel where many of the ‘classic’ glassy Vox tones are to be found, but it is somehow organic and satisfying. You just forget about the amp and play the instrument: it’s all in the fingers and what you do with the volume and tone controls. If you want a bit more drive, the Boost control provides a modelled germanium‑transistor treble boost into the front of the amp that works just as you’d want it to, without going over the top. The slightly ‘blank‑canvas’ Normal channel does make a great partner for an overdrive pedal in front, too.

Move the Channel switch up to Brilliant and the Bass and Treble controls come into play. If you’ve used the real thing, be prepared for the eccentricity of their behaviour, perfectly replicated here. Both full on isn’t maximum bass and treble, but a big low‑mid suck‑out: these were early days for guitar‑amp design! Boost comes from a nicely modelled Maestro Echoplex EP‑3 preamp stage, which adds colour and a bit of ‘heft’ to the sound. So many brilliant (literally) sounds in here. You could play for years and never find them all. Absolute heaven with a Tele. If you are a Vox fan, you’ll know the players and ‘vocabulary’ of the sounds. If you are not, it’s here for you to discover just how fabulous and individual it is.

The Vib channel brings into play Vox’s version of a vibrato/tremolo circuit, neither optical nor bias‑based like Fender’s designs, but something derived largely out of phase‑shifter circuitry originally designed for use with electronic organs and accordions. As in the ’65 Deluxe, moving the middle switch up to the Alt position repurposes the Treble and Boost controls as Speed and Intensity. Like most things on a Vox, it’s a bit different and certainly rewards experimentation. Try setting the Speed in the middle and start with the Intensity all the way up, and then turn it back to the middle, observing how it appears to get faster, rather than less intense, and change waveform.

There’s no spring reverb on an AC30, so here we have UA’s really lovely Dynamic Room Modelling, as used in their OX processor, and based on UA’s own 610 studio in California. The room simulation is spectacular, and just lifts you out of the dry sterility of close‑miking into a playing comfort zone when recording. You just have to remember that it is baked in to the output, and you may want to dial it back to fit the context of a track. Like the Dream ’65, the Ruby Vox has glorious tube‑rectifier ‘bounce’ that makes playing feel so much more like a real amp than a modeller.

Woodrow ’55 (Tweed Deluxe)

The Deluxe was Leo Fender’s first amp design, and went through a number of iterations before arriving at the favoured 5E3 circuit, housed in its classic ‘tweed’ livery. It’s a really simple circuit, with no reverb or modulation, a single Tone control and a high‑impedance microphone input alongside its instrument input. Unless you are familiar with these amps, you might think the inclusion of the Mic input’s volume control in the modelled pedal somewhat irrelevant, but the interaction of the two volumes is actually a really important part of the Tweed Deluxe sound. The channels are automatically ganged when you turn both volumes up, but you can hear either alone just by turning the other one all the way down. The use of a low‑gain 12AY7 tube as the input stage in this design keeps the clean sound really sweet, with the fixed bright capacitor on the Instrument channel able to be balanced out by also advancing the Mic channel. The highly characteristic and quite complex interactions of this input stage are exactly replicated in the pedal, with the single Tone control also playing its part in determining the overall drive level of the amp.

The Woodrow ’55 Instrument Amplifier models all the subtle nuances of a Fender 5E3 ‘Tweed’ amp, including the interaction between the instrument and mic stages.The Woodrow ’55 Instrument Amplifier models all the subtle nuances of a Fender 5E3 ‘Tweed’ amp, including the interaction between the instrument and mic stages.It is quite hard to imagine a single amp being able to deliver both Larry Carlton’s sweet sustaining cleans and leads of the ’70s and Neil Young’s guitar mayhem, but they are both very characteristically Tweed Deluxe. It’s that range, and the ability to find all the nuances in between, that has kept the Tweed Deluxe as one of the most favoured recording amps of all time. It can get very ‘spitty’ when pushed hard, but that’s just part of what it does.

Speakers on offer here are 15‑watt Alnico, the original Jensen, or a 25‑Watt Celestion ‘greenback’, all in a 1x12 tweed combo housing, plus a 4x12 ‘British cabinet’ with Celestions, a 4x10 tweed ‘Bassman’‑style combo cab, and a JBL in a 1x12. Plus, of course, no emulated cabinet/mic, for use into an amp. Mics, pre‑selected by speaker type, are drawn from a range of Shure SM57, Sennheiser 421, AKG C414 and Neumann U67.

The Boosts available in this model all drive the input of the amp: a Korg SDD‑3000 preamp stage (a popular ’80s rack delay unit) also automatically selects a virtual low‑sensitivity input. In all other instances, you are connected to the ‘Hi’ input. The Boost line‑up is completed by a Maestro Echoplex EP‑3, and a clean ‘curve’ boost that rolls off bass and increases treble and mids as you increase the Boost level, which helps to some extent to alleviate the Tweed Deluxe’s notoriously ‘flubby’, loose bass end. The pursuit of ultimate reality in emulations is not without consequence, and players who have only ever used modellers might be surprised to find that ‘everything on 11’ doesn’t automatically get you a ‘sweet, singing lead tone’: in the real world, it often gets you a brittle, flubby mess. And it will, too, in anything where the modelling is truly accurate. This one can get very raw!

Finally, as with the Vox, since there’s no integral reverb to emulate we get the lovely UA room simulation. It’s so good for combating the unnaturalness of a DI’d situation — quite hard to say if I’d miss the room or the spring more, if the Dream ’65 had the room instead. Now I just want both! The Woodrow ’55 really is a delightful little amp, full of nuances and historic tonal references. If you are auditioning this one, be sure to spend some time in the ‘cleans’, juggling the two volumes. There’s so much that’s great in there, with humbuckers and singles alike, and I’m convinced that the dynamic speaker‑modelling process gives you something in the clean tones that IRs, even really good ones, just can’t.

I’m convinced that the dynamic speaker modelling process gives you something in the clean tones that IRs, even really good ones, just can’t.

The Real Thing?

Ask any 10 guitarists to identify their favourite amp simulator and you’ll probably get nine different answers — and two of them will be “None: nothing sounds like my real tube amps.” But perhaps it shouldn’t be a surprise, given the sheer variety of real amps that the market seems able to support. What each of us looks for in a guitar amp is obviously very personal, and there is no reason why that should be any different when seeking to replace a real amp with a digital simulation. But if there is a consensus, it is that digital modelling of guitar amps and speakers has come a very long way in the last few years, and for many players our choice is no longer a case of “Is that good enough?” but rather “Do I like that one better than this one?” You’ll notice I haven’t referred to any digital spec or latency figures in this piece. That’s mainly because I couldn’t find any — apologies to anyone who feels they absolutely need to know this stuff, but once something sounds and feels so completely right, maybe it just doesn’t matter any more!

The inclusion of multiple amp emulations in hardware digital modellers from day one may have created a culture of expectation that perhaps doesn’t now quite fit the real‑world experience. Many of the people I know who do actually use modellers extensively have eventually gravitated towards using just one or two virtual amps, with subtly different settings, rather more closely replicating the experience of using just a single real amp and maybe some pedals for variety. Inevitably, people will look at the price and format of these UA pedals and make a comparison with the seemingly ever‑increasing number of very nice multi‑amp digital emulations you can get for the same money or even less. But that would rather be missing the point. I think these are for a different user: one for whom detail and nuance in the sound, and touch and feel in the playing is everything. Someone who will relish investing perhaps years of playing into making one of them ‘their amp’ and ‘their sound’, just as many of us have done with our versions of the real thing. There is certainly more than enough ‘real thing’ in these emulations to make that a deeply rewarding investment.

Can I Use Them With A Real Amp?

Connecting to an amp: what UA call the ‘4‑cable mode’.Connecting to an amp: what UA call the ‘4‑cable mode’.The stompbox format and ability to defeat the speaker/mic/room emulation mean these devices are obviously envisaged for connection to real guitar amps, as well as for DI recording. So what are they like in that context? In a word, superb!

Connect to an effects return if possible — the suggested ‘4‑cable mode’ works great to allow you to use these as a switchable alternative to your amp’s own preamp — but it can still work if you have to go in the guitar input of an amp, especially on non‑master‑volume models. Try using the low‑sensitivity input and, on Fenders and anything with a similar tone stack, turning bass and treble to zero (keep the mid control on maximum, if you have one). Remember, there is still an emulated power amp running here, so it tends to work best with amps that aren’t already distorting too much. They all work well: the Deluxe into a Deluxe, not surprisingly, but the Vox into the power amp of a Mark series Boogie is a special delight, maybe because it offers up a kind of chime and grind that the Boogie on its own can’t get near. Unlike many digital pedals, they have very low noise in this configuration, too.

All in all, I’d say these are the most analogue‑sounding and feeling digital things I’ve ever used in conjunction with a real tube amp. They have real dynamics at performance levels, which is where so many modellers fall down.


The Strymon Iridium, Boss IR‑200, Atomic Ampli‑Firebox MKII, Line 6 Pod Go, Walrus ACS‑1, and undoubtedly a few more that I’ve forgotten, will all give you very decent emulated amp and speaker sounds for a similar price.

UAFX Ruby | Audio Example

There are already plenty of heavy-distortion, or sparkling-clean audio demos of the new UAFX amp sim pedals all over the web, but here’s the ‘in-between’ that’s really what I love about these. Everything is under the fingers: dig in and it will spit and grind, lay off with the right hand and a Tele bridge pickup can have the ‘big, fat clean’ of a pedal steel. Within a cluster phrase, each note still has its own tonality. That’s what real amps do (good ones, anyway), and that’s what I’m hearing here, too. Dave Lockwood

  • Recorded to DAW via a two-channel DI box straight from the stereo output of the pedal, with no recording or mix processing.
  • This is the Ruby pedal’s Vox ’64 Top Boost channel. Volume at 80%, Bass and Treble centred, no boost pedal. The Cut control is around 10%.
  • Dynamically modelled Celestion Alnico Blue speaker, with Shure SM57.
  • UA pedal room sim at 40%.
  • Tele, bridge pickup, with guitar volume control backed off to about 70%. With the amp fairly wide open, but under-driven, this makes for a very touch-responsive tonality.

Track © Dave Lockwood/


  • Very convincing miked amp and speaker sound for DI recording.
  • Work equally well with a real amp.
  • Detailed amp ‘feel’ and performance emulation.
  • Robust build quality.
  • Intuitive, amp‑like user interface.


  • Limited app features.
  • No wired app connection.
  • ‘One amp per pedal’ format.


Since most of the modelling world seems to be in an arms race to offer more amps, effects, IRs, connectivity and controllers, these are a bit of a statement! UA appear to be calculating that there are players who weigh up the price, facilities and, above all, sound balance quite differently, and I think they might be right.


£345 each including VAT.

$399 each.