What is an Amp in a Box

The Universal Audio Woodrow, a ‘55 Fender Tweed in a pedal.

I really dislike the game of Buzzword Bingo. It happens in every industry. In the guitar industry we have been inundated with this load of hoo ha for a long time, with authentic, iconic and vintage tossed around like dressing at the salad bar. These words are used so much, they no longer have any real meaning. When people hear them, the needle on the BS detector flies into the red and bounces off the stop.

The latest in this collection of dog dung is “Amp in a Box” What does it really mean? Is this a thing? Or is it just more mcmarketing mumbo jumbo?

Let’s talk about that.

As best as I can tell, the phrase has rapidly become somewhat meaningless as it is used to describe many things that are allegedly similar, but are not.

Amplifier Definition

If we want to be pedantic about things, and we need to start somewhere, an amplifier is a device that takes a low level signal and manipulates it to be a higher level signal capable of driving a set of speakers so listeners can hear the signal as was intended by the recordist.

In the context of an instrument amplifier, the device takes a high impedance signal and feeds it to a preamplifier. The preamplifier increases the signal and typically includes a tone stack of some kind. It may have a simple single volume control, or a combination of volume or gain and a master volume. In either case, the volume or gain control allows the user to drive the preamp input to achieve a tonal characteristic of the preamp when loaded into what we call overdrive, which is basically signal clipping. Or not as some preamplifiers are designed with a lot of headroom so they stay clean even at maximum gain. The addition of a master volume simply allows the output signal to be reduced to control overall volume. In order to drive the speaker(s) the signal then goes to a power section to generate a much higher level of output capable of driving the speakers to a level suitable to the player / listener.

Preamp and power amp sections can be powered by tubes (valves), solid state (transistors) or digital signal processors. There are champions of each type and not a little bit of prejudice in terms of what is “best”. Valves and solid state do sound different when comparing an output signal. Digital Signal Processing (DSP) has no defined characteristics because to date they are programmed to sound like something else, or in some cases, multiple something elses.

The output transformer in a valve or solid state amplifier in combination with the speakers define the amp “sound”. While much is made of different preamp design strategies, what we hear in the real world is mostly impacted by the output transformer and the speaker systems in use. These facts are painted over by subjective perception because of what we think we hear. As we know, auditory memory is a pretty picture that isn’t all that robust.

That said, many people equate a sound to an amplifier. Amplifiers in this context also include the speaker systems as an amplifier without a speaker is somewhat useless from a listening perspective. Consequently we find comments that refer to the complete system such as “the Fender Deluxe Reverb is the greatest amp ever” or “there is nothing that sounds like a 100watt Marshall head into a pair of 4x12 cabs”. Whether you agree or not is somewhat immaterial because enough people have decided these things to be true that there is a market for the reissue (new builds purportedly based on old designs) units, or increasingly, a device that puts out a signal that sounds like the original without you having to buy one and cart it around.

Amp in a Box Potential Types

ZVex ‘59 Sound

The first kind of amp in a box thing is a pedal, or activatable box, that goes between the instrument and your existing amplifier. These devices most commonly are designed to emulate the preamp, power amp and speaker system of a specific amplifier. Consider a pedal that says it makes what you have sound like a 1959 Fender Bassman. A very popular example is the ‘59 Sound from ZVex. It’s not exact of course, because your existing amplifier has its own unique preamp, power amp and speaker system, none of which are the same as a 1959 Fender Bassman, unless of course your amplifier IS a 1959 Fender Bassman in which case you do not need the pedal anyway. I’m not pitching rocks at these devices. You could very well find one that sounds brilliant to you, and if that happens, you have won, but to call them amp in a box is somewhat misleading because you still need an amplifier.

UA Dream ‘65

There is a newer iteration of this kind of device that does what the first type does and while it can still be connected to an existing amplifier is designed from the ground up to be used either into a powered FRFR speaker, a recording desk or straight into a PA system. In addition to using circuitry to sound like the original preamp and power amp, they use IRs (impulse response) digital files to sound like the original speakers. An example of this is pictured here, a Universal Audio ‘65 Dream which purports to be a 1965 Fender Blackface amp in a box. A subset of these devices, such as the Captor units from Two Notes engineering, use your existing amplifier and bring you the sound of different speaker cabinets. Since the speakers used and the cabinets contribute so much to what an amp sounds like, this does allow the player to effectively have a room full of speaker cabinets. Mostly Captors are used to feed a recording desk or a PA, but can also work with FRFR speakers. They are an excellent solution if you are looking for the sound of different cabinets and the company has done a nice job with the IRs that they sell to be very accurate simulations of the real thing.

Neural Quad Cortex

Another Amp in a Box is something quite different. In a standalone sense these are referred to as digital modelers. They use DSP processing to sound like the preamp, the power amp and use IRs to deliver the sound of the real amplifier system. Rather than a preprogrammed single tonal value, they use profiles built by following a specific process to record the real amplifier and speaker system, codify that into a profile, and then use the DSP engine to simulate the entire amplifier section. Examples here include the Kemper Profiler and the Neural Quad Cortex.

Speaker Simulations

The challenge with speaker simulations is always the accuracy of the coding that creates the simulation. The longer the IR file length, the better the odds of getting the simulation close to the real thing. The better the job done on the profile, the better the odds of an accurate simulation. We must however remember that while they may be close, you can set six “identical” cabinets side by side and they will all sound subtly different. Many reviewers continue to use effects, and modify the EQ when doing this, or employ overdrives and while these are what will happen in the real world, any divergence from a flat clean signal is going to make accuracy judgements very difficult. We also need to recommend that the speakers from a real 1959 Bassman, or original Marshall 1960A cabinet are now 50-60 years old and no longer sound as they did when they were new. In this context, speaker simulation is more like a game of horseshoes than photocopying.

Why Bother with the Amp in a Box?

Cost and space come to mind immediately. I will be blunt and say I do not buy into any amp in a box that is used in front of an existing guitar or bass amplifier because in the end that real amp’s output transformer and speakers are going to put colour on things. That does not mean I will never like the tone, but it does mean that I will never get the full experience of the real thing. It might be close, and that may be enough.

I like the sound of real amplifier systems. They push air and make noise and there is a human visceral response that comes from that. No matter how good an amplifier simulation is, it will never feel like a 100w Marshall Plexi into a pair of 4x12s or a Vox AC30 turned up all the way, or a high headroom clean amp like a Fender Blackface Twin with the volume up. All those things are wonderful. They also promote hearing loss, annoyed neighbours and the development of a personal relationship with local law enforcement.

Where the Amp in a Box, or modeler really excels is in getting the sound of that real amp at its best volume is in its ability to do so without the volume issues. I do not own any of the second type of Amp in a Box devices, but I do have a Helix, a Kemper and a Quad Cortex. The complaint I hear is that they don’t feel like the real thing. Maybe. However, I have yet to have a person be able to listen to the same tune, played on the same guitar recorded with both a Quad Cortex and direct from a real amplifier be able to tell me which is which and the honest ones say that they really cannot hear a difference in the recording.

Most modelers are used into a DAW, or used directly with headphones. What we hear in headphones can be accurate but doesn’t feel like a 4x10 or 2x12 cabinet pushing air. So I did an experiment. I got a profile for the Quad Cortex for each of several amps that I own. Specifically I tried different profiles until I found one that sounded like my actual amp when recorded with the same microphone as used in the profile. Let me be clear, that all profiles are not created equal. Some are in fact much better than others.

Then I plugged the guitar into a Radial switcher. The switcher went to the amp on the A side and to the Quad Cortex on the B side. Instead of going from the Quad Cortex into a DAW, I ran it directly into a pair of HeadRush FRFR speakers. While the Quad Cortex has stereo by default, I used a mono configuration and used no effects on either side to colour the sound. With the HeadRushs turned up to be as close to amp volume as possible, which in fairness was done on a weekday during midday hours to avoid noise complaints, I switched back and forth. I did not power the switcher, so while I could stomp on the switcher, it was not obvious to me after a few minutes which switch position was which.

HeadRush Powered 12'“ FRFR Speaker

With the FRFR speakers pushing air, and being driven at a volume like the real amps, it was quite difficult to tell the difference in the room between the Quad Cortex and the real amps. I could feel the air moving, feel the vibration through the floor and feel the sound in my bones. I cannot tell you that the pairings were identical. They were not. I could always tell a difference. However neither option in the pairing was unpleasant and both sounded really really good. I did not compare solid state guitar amps to the Quad Cortex simply because I do not own any. I only compared tube amps. In my case the real amps were a 1964 Reissue Fender Blackface Twin, a mid 70’s Marshall Custom Super Lead Mk II into a 1960A and 1960B cabinet set, a 1959 Reissue Fender Bassman and a handwired VOX AC30. The pairing that were most different was the case of the pair of JBL FRFRs vs the two Marshall 4x12 cabinets. They were close, but those old and battered 1960A/B cabs were different from the profile. Not by much, but different. Certainly not in a bad way, and I have enough experience with early 1970s Marshall cabinets to know that they are not all the same anyway.

Conclusions

For me, the idea of an amp in a box is a decent idea, so long as it does not end up feeding an existing guitar amp. At that point, it’s not an amp in a box to my mind. If that amp in a box feeds the DAW or the mixing desk directly and delivers sounds like the real amp, I am in. These include devices like the Strymon Iridium or the BOSS IR-200 or the Walrus AC-1. I am looking forward to trying out the new Universal Audio devices when available in Canada. They have three models, one for a late 50s Fender Tweed, one for an AC30 and one for a Fender Blackface Deluxe.

However for spatial efficiency and value for money, I still think that I am furthest ahead with the Kemper or the Quad Cortex. They are very accurate, both record extremely well, and both have a lot of profiles that you can try to find the ones that suit your requirements best. They also have plenty of horsepower so latency is not an issue.

Does this mean that a roomful of tube amps will be coming available for sale? Not in my case so long as I have the space. It’s not a question of either / or. For me it’s only and.

Thanks as always for reading and until next time, peace.