The dynamic speaker and mic modelling of UA’s popular OX amp‑top box is now available in a compact pedal format.
The OX Stomp takes the dynamic speaker modelling of UA’s OX amp‑top dummy‑load, attenuator and speaker simulator and puts it into what’s now a familiar UA six‑knob, double‑footswitch enclosure. Just to be clear, though, this is not an OX somehow miraculously made smaller: there’s no dummy load, so you can’t plug the speaker output of an amplifier into it. This is a line‑level (or below) device, designed to accept the output of a preamp or guitar‑amp simulator pedal. Don’t UA make some of those, with OX‑derived dynamic speaker simulation already onboard, you might be thinking? You’d be right, of course, and very good‑sounding they are, in my opinion, although the OX Stomp’s wider range of cabs and miking choices offer a lot more flexibility than the onboard choices of the UA amp pedals. There are plenty more really useful applications for this little box, though: most obviously, you can put it after a dummy load/speaker attenuator, with due attention to signal levels, and enjoy most of the functionality of the full‑size OX. You can feed it the output of an ‘amp‑in‑a‑box’ pedal, but preferably one that replicates an output stage rather than just a preamp. And, finally, you can use it with amp‑modelling devices from other manufacturers, many of which may benefit from a more sophisticated and detailed speaker‑sim process, especially those from before the era of really good IR‑based (impulse response) speaker simulation.
Guitar‑speaker IRs are, in effect, just a very detailed frequency response curve derived from a digital recording of a guitar speaker that can subsequently be imposed on the sound of a guitar amp or simulation, and their widespread adoption has had a transformative effect on the usefulness of direct‑recording devices for guitars. The speaker simulation in UA’s original OX product, however, is not IR‑based, but uses a real‑time modelling process that allows it to respond dynamically to varying input signals, replicating the behaviour of real speakers with more detail and accuracy than the static ‘snapshot’ of an IR.
Making Connections
The OX Stomp has a limited number of physical controls on board, with much deeper, detailed control and editing available via the UAFX Control app.Like all the larger format UAFX pedals, the OX Stomp has stereo I/O on unbalanced quarter‑inch TS (tip‑sleeve) jacks, so stereo inputs can be maintained in stereo, whilst a mono input can benefit from the onboard room simulation in either stereo or mono. Recognising that users may want to employ guitar pedals, not just true line‑level devices, as a source, there’s plenty of range in the internal operating level; you just need to be prepared to turn up the output control a long way with lower‑level signals. There’s no level metering on the pedal or in the app, so I just used the position of the output knob when feeding a line input at unity gain as a guide: if I was turning it below halfway to get a sensible externally metered level, there was probably too much going in. In theory, I guess the input level should make a difference to the ‘dynamic speaker modelling’, but provided that I wasn’t too far to either extreme it all just seemed to work as expected. As usual, there’s a USB‑C port for registration and firmware updates only, so no MIDI or digital I/O, and you’ll need to source your own 9V DC external power supply with a current capacity of at least 400mA.
Like the OX amp‑top box, the OX Stomp has a limited number of physical controls on board, with much deeper, detailed control and editing available via the UAFX Control app, but it does still include all the virtual speaker cabinets, microphones and effects of the original unit. Physical controls consist of a level knob for each of the two virtual close mics, plus another (stereo or mono) for the room miking setup, Speaker Drive amount, simulating speaker condition, and an overall output level. In addition, a three‑way switch for each virtual mic allows you to choose Dynamic, Condenser or Ribbon as the mic type.
The OX Stomp is built around the concept of the Rig: a complete setup of virtual speaker cab, two mics, room ambience and effects that can be stored as a preset and activated via the footswitches or the UAFX Control app.
The OX Stomp is built around the concept of the Rig: a complete setup of virtual speaker cab, two mics, room ambience and effects that can be stored as a preset and activated via the footswitches or the UAFX Control app. The Rig knob in the centre of the pedal selects any one of the six presets currently loaded into the pedal as the ‘active Rig’. Given that the OX Stomp has neither motorised pots nor virtual, LED‑ring pots, it will be apparent that the knobs and switches won’t always match the sound of the preset. In fact, they almost never will unless all your presets are basically the same or you’ve just saved the current setup, which you can do either by pressing and holding the active Rig footswitch until the LED flashes, or within the UAFX Control app.
Rigs saved via the footswitch retain their edits in the pedal itself, but don’t get added to the app’s user library until you also save them in the app; your edited version will still be there in that position on the Rig dial even if you have powered down the pedal. You can subsequently find your temporarily edited Rig in the app because it will have an Edited legend, highlighted in brown, beside it in the list. As‑yet‑unsaved edits made in the app rather than the pedal get highlighted in red. Easy temporary saving seems like it could be really useful in a live performance situation where you might just want to tweak and save the level of a preset rather than doing any deep editing, which you can do without having to involve the app.
Control App
The UAFX Control app is where you have access to the full line‑up of cabs, mics and effects. Tap the Edit legend at the bottom the screen and you’ll see the current cab, mics 1 and 2, plus the room mic(s), as well as the option to tweak the master level, add EQ, compression, delay and reverb. Twist the Rig selector while you are in this screen and you’ll see everything update as you go round. To edit you choose a basic cabinet type from a graphic menu of 1x12, 2x12 and 4x12, and tap the one you want from the images and descriptions presented. Do the same with the mics, only here you have further options in settings for level and pan, as well as a low‑cut filter and off‑axis positioning. In the case of the room mic, off‑axis becomes Damp(ing) to rein back the liveliness of the room sound by adding some virtual baffles and carpeting. The mics have individual pan settings, so if you’re outputting in stereo, you can send each one out of a different output, which allows separate post‑processing in your DAW mixer. You’ll also have to fully pan them if you want to maintain the complete stereo width of a stereo source. It pays to be aware that some of the factory presets are hard panned, so you’ll only hear one of the mics if you just have a mono connection.
The app gives access to the full line‑up of OX cabs, mics and effects, but with a simplified interface for use on mobile devices.
Master EQ is a four‑band affair, plus high‑ and low‑cut filters, whilst the compressor models an 1176 with the usual control set: input, output, attack, release and ratio, with settings of 4, 8, 12 and 20:1, plus the infamous ‘All’ for all ratios selected at once. The EQ stage here is post‑cabinet, pre‑effects, so akin to adjusting a console channel EQ on a miked‑up amp, but there’s no indication of the actual frequency of any of the bands. Of course, you can do it by ear if you’re just being creative, but if trying to solve a problem at, say, 750Hz, you won’t know if ‘Mid’ or ‘Low Mid’, or neither, will do the job. The delay section has plenty of options: Dual, Crossover, PingPong, Chorus and Flanger, but no delay‑time readout, just 0.14ms at one end and 3.0 seconds at the other. Personally, I’d happily lose the choice of six modulation waveforms for a bit more basic information. There are independent settings for two delay channels as well as the ability to link them, plus Mix, Feedback and Modulation Rate and Depth. Practical delay mixes exist primarily in the bottom 10 percent of the slider. I’m not sure how often you’d use any of the other 90 percent unless you were using 100 percent wet in a ‘wet/dry’ setup. Reverb offers Decay time, stereo Balance, Treble and Bass EQ and Mix, with the wet/dry Mix parameter having a sensible scaling (15 percent wet is at the halfway point), which gives you plenty of resolution around the likely working area. I’m not sure why that hasn’t been done for the delay as well.
Unlike the ‘full‑fat’ OX app, this is not a graphics‑rich interface. All parameters are presented on horizontal sliders that are, admittedly, more practical for a small‑screen mobile interface, but still are not an efficient, precision UI in my experience. That said, there’s some useful double‑tap and tap‑and‑hold implementation that offers instant resets or finer‑resolution operation. In practice, as a relatively light user, the thing I miss most in this interface is a gain‑reduction meter for the compressor. It’s always difficult to hear the onset of compression on a single‑instrument signal, which makes subtle settings become guesswork. If we can’t have a proper gain‑reduction meter, then just flashing or pulsing something on screen to indicate the signal rising over the threshold would be a whole lot better than nothing.
It offers a degree of instant adjustability and fine‑tuning that goes beyond anything you can conveniently achieve by swapping one IR for another.
Applications
Direct recording using a guitar‑amp simulation preamp/pedal (or a real amp with a load box) is one obvious application for the OX Stomp, but with ever more venues being volume‑restricted or even going ‘silent stage’, the use of amp modelling in live performance is ever-increasing, and the OX Stomp clearly has a role to play there too. Mounted on the end of a pedal chain that includes an amp simulator (with its own speaker sim switched off) OX Stomp offers a degree of instant adjustability and fine‑tuning that goes beyond anything you can conveniently achieve by swapping one IR for another within a modeller or IR loader, even without using the UAFX Control app.
The OX Stomp’s unbalanced outputs mean you’ll want a DI box (or two, if stereo) for a feed to the PA of any significant distance, and if you are using a powered, full‑range, PA‑type speaker as an on‑stage monitor, you can just hook into the speaker‑emulated signal via the DI box’s thru connector. Whatever’s going to front‑of‑house is then also going to your monitor(s): speaker sim, miking and effects. If your preferred way to use a modeller on‑stage is feeding a power amp and real guitar speaker, whilst still wanting to send a speaker‑simulated signal to FOH, you can obviously split the signal at the modeller output and send separately to your stage rig and to the OX Stomp for the PA. Of course, you won’t then hear any of the effects that may be in the PA feed in your on‑stage sound, but there is a neat workaround. The inclusion of a neutral‑sounding virtual DI box as one of the ‘microphone’ choices in the app allows you to set up a hard‑panned virtual cab and mic signal feeding one OX Stomp output, going to the PA, while the other output carries a ‘clean‑feed’ version using the virtual DI to your on‑stage power amp and speaker. Both outputs will then have the effects in them. Both signals will now also be mono, but personally, I wouldn’t ever be too precious about that in a live‑sound environment. You will need to create dedicated Rigs specifically for this scenario in the app, although if you never use stereo, there’s no reason not to create all your rigs like that.
The OX Stomp can be used to add UA’s dynamic speaker modelling process to other modelling units that have IR‑based speaker simulation.
There’s a lot of flexibility in the footswitch programming. Each one can toggle between a single Rig and bypass, or between two Rigs in A/B mode, and as there’s a second footswitch, that means you can have four Rigs on tap for footswitch recall, with the second one being designated as in C/D mode. Alternatively, one footswitch can be set to A/B toggle two rigs, while the other switches Delay, Reverb or All Effects on and off. If you don’t need to switch Rigs at all, you can program one footswitch to toggle Delay on and off, while the other does the same for Reverb.
Keep It Simple?
The app’s factory presets are often a good starting point for tweaking any sound to your own requirements.Bringing a lot of the functionality of the OX, with its intuitive, graphics‑rich interface, into the more constrained world of the mobile app was always going to be a challenge. The joint functionality between the pedal and the app feels slightly more complex than the other UAFX pedals: this one can access multiple presets for instant recall from the hardware. Of course, you don’t have to use everything it can do. Unless you really must swap out your speaker cabinet from one song to the next — something I have to say that I’ve never wanted to do in live performance — my ‘Super Simple Guide To OX Stomp’ says use the app initially to select the speaker cabinet you like best, assign it to all six Rigs on the dial and shut down the app. Now you can play with the mic‑selector switches and level controls, the room sound, and the Speaker Drive parameter and output level until you hear something you like. Save it, if you want, by pressing and holding the left footswitch, and move onto the next Rig position on the dial to do the same again. Or just carry on playing through Rig 1, because it is already doing exactly what you want in replicating the sound of a miked‑up speaker cabinet.
Of course, there’s tons more you can do with the OX Stomp via the app, but you can still do a lot just from the hardware alone. If there were just one thing I could change here it would be that by default both hardware mic switches select from a choice of the Dynamic 57, the Condenser 67 and the Ribbon 121. If the second mic switch defaulted to the app’s alternate choice in each category (Dynamic 421, Condenser 414 and Ribbon 160), you’d instantly have more choices when running in ‘hardware‑only’ mode.
If it seems like I’ve mentioned ways to avoid using the app rather a lot, it’s because that’s what I actually do with these UA pedals. I’ll use the app to make a few fundamental settings and then just use the pedals as hardware, thereby avoiding the frequent restarting of the host device and Bluetooth pairing that seems to be the only way that I’ve found I can manage to keep the app connected. I hope UA manage to improve on this soon, but in the meantime I prefer to think of it as in ongoing development and not to be relied on more than necessary. It is the sheer quality of the sound that makes me want to use these UA pedals. Anything else is secondary.
How Good Is OX Stomp?
Like any digital processor, the OX Stomp has some latency (under 3 milliseconds), and it pays to be aware of that number in what you choose to partner it with. Another UA amp pedal will add the same amount again (digital effects with analogue dry thru don’t add anything unless set 100 percent wet): this is still acceptable, until perhaps you add something else, like a trip to a digital FOH mixer and back, and then wireless in‑ears. All latency is cumulative, and even studio monitors that have significant DSP on board have a small amount of it! An analogue source is an obvious option to consider, but you may be disappointed if you just feed a drive pedal or preamp into the OX Stomp. Ideally, you want an analogue pedal/processor that replicates a power‑amp stage as well as a preamp, but without an integral speaker sim — or at least with one that can be switched off.
I had great success using an Origin Effects RD Compact, and even a SansAmp Classic — the latter can’t defeat its speaker sim, but it is so sonically ‘neutral’ that the OX Stomp can still give it some ‘real speaker’ characteristics. You can even dramatically improve some of the amps in an old Line 6 Pod (though for others it’s less successful, as if the amp voicings have already been skewed to overcome the limitations of some of the onboard speaker sims). The OX Stomp can also be a great learning tool: turn off all the mics and you hear nothing; turn them up one at a time and compare a 57 with a ribbon, or listen to what the room mic really adds by hearing it with the close mics turned down.
So, how good is the OX Stomp? It is very good at what it is designed to do. But the success of what it is designed to do is very dependent on what you put into it. A version of the OX Stomp that also modelled a tube power‑amp stage would work better with a wider range of sources and probably satisfy more users — maybe that’s one for the future. But what we have right now certainly does what I expected of it. Personally, I could live forever just in Preset 1: ‘4x12 Green Punch’. Now that’s what a perfectly-miked 4x12 should sound like!
AUDIO EXAMPLES
To check out the OX Stomp yourself, I have created several audio examples. You will find them here.
Pros
- With the right source, it offers top‑class miked speaker sounds that can be DI’ed.
- Makes UA’s Dynamic Speaker Modelling more affordable.
- A useful amount of control available from the hardware.
- UA‑quality effects on board.
Cons
- The UAFX Control app is a work in progress.
Summary
UA’s excellent speaker and mic modelling from their OX amp‑top box in a compact pedal format. Feed it something that sounds like an amp and it can take you all the way to a polished, pro‑engineered guitar sound.
