The Replay Box Story

United's Chad Kelly discusses the origins of the Replay Box.

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My involvement with reamps goes back more than 20 years... an experience working on a record in a Texas studio which had a pair of reamp units that were common at the time. I had owned one of the earliest commercially available units as well, and used it for many years in my home studio. I felt both were lacking in certain ways that really frustrated me in the studio. I felt that none of them really had sufficient gain and almost always required a boost pedal following the reamping device, which added further noise and THD.

I also felt that they had a somewhat pinched and midrange-focused tone, which may have been OK for electric guitar, but not so great for bass guitar or anything else that you might want to throw at it. There was also some noticeable phase shift or phase inversion in the operation of these early units I worked with.

I really felt that a reamping device should do 3 very specific things.

1.) It should offer true ground isolation from input to output for cases where there is a potential for ground loop between the control room and tracking room. Most of the commercially available devices had a ground lift of sorts which may have lifted the chassis from the pin 1 (something that very rarely solves anything); but nothing really provided true ground isolation to break up potential ground loops.

2.) It should have sufficient passive gain. Knowing that the incoming +4 balanced signal should in theory have enough energy to drive the instrument input of an amp, I did not like the fact that most available devices had to throw away so much level that an external boost pedal wound up becoming necessary, inviting a lot of unnecessary noise and interference. I understood the reasons for doing so were based out of the need to isolate the source from the destination; but knowing that there has been a lot of advancement in how transformers can be designed and wound, I felt that there was a better way of doing this without sacrificing as much level. 

3.) It should be absolutely sonically neutral. The whole idea of these units is to fool an amp into believing it has a guitar plugged into it. It doesn’t need to be voiced for guitar, because the recorded DI signal ALREADY IS voiced for guitar because it IS a guitar… and guitar is only one of many things I like to reamp. I reamp bass, I reamp software and analog synths into a keyboard amp, and I have even reamped snare and kick drum and vocals for effect. A reamp also should serve as a studio interface between the recording studio and the guitar pedal world. So for that reason, the reamp has to be invisible to this process.

Starting from scratch

So with these criteria in mind, I set out to start figuring out how to make my own unit. The first units I made were overly complicated, utilizing quite a few semiconductors (resistors, capacitors, inductors, transformers, pots, switches, and more); but over time the design continued to be simplified, while consulting with transformer companies, until just about everything I needed could be done with just the transformer. For many years, I manufactured these by hand, on request, and it was sustained purely through word of mouth. These units became a secret weapon for many big-name producers and engineers; but were never really available to the public and never widely known about.

The design was relatively stable for many years, and boasted a near-unity level output, which was far more gain than any other commercially available unit at the time. It was only after listening to one popular recording studio engineer and influencer, that I realized my box probably still needed a bit more gain. It dawned on me that while a +4, balanced signal should in theory be much hotter than an instrument level, unbalanced signal; in reality it may not be loud enough just due to how insanely dynamic a direct guitar pickup signal can be. If recorded diligently, ensuring no clipped peaks, the average of the signal can be vanishingly low just due to this extraordinary dynamic range of the completely un-distorted, uncompressed dry signal.

Pushing the transformer

After consulting again with our transformer winders, and much trial and error, we were able to push the limits of what this transformer could do, by winding an additional set of secondaries to the transformer that could double the amount of available gain on tap. We experimented with making the transformer even hotter still; but discovered that any more gain beyond this would begin to cause pretty noticeable artifacts. We knew, at long last, that we had squeezed every bit of performance we could out of this basic design concept. 

Somewhere during the long gestation period while these products were being made by hand, I experimented with making a version of the reamp that had intentional color, to juxtapose against the standard version which was extremely transparent. Some of my earliest handmade units from 20 years ago used an inductor and a switch to offer a warmth mode; but the considerable amount of signal loss (which had to be matched on the clean channel) was something I hoped to avoid this time around. I was able to find an obscure telecommunications transformer that had the inductance specs I was looking for that could be used in place of my standard transformer, when configured in a pretty unorthodox way. This deliberately colored version of the reamp offered even slightly more gain on tap, as well as enhancing the signal with some subtle warmth and thickness.

This model became known as the AngReAmp, aptly named by one of the first customers who acquired one. It became popular with indie rock and metal, and with folks who liked to experiment more with their recording techniques. I found it to be a great way to add some thickness and depth back into thinner sound DI captures that may have been a bit anemic due to passing through cheaper pickups, direct boxes, or preamps on the way in.

20 years on, the Replay Box is ready for prime time.

Now, after more than 20 years, these boxes have been combined together for the first time, into one unit and made commercially available for the first time. A secret weapon only known to a handful of successful producers and engineers for decades, the RePlay Box is the final word on this novel reamping circuit approach that is considered by many to be the very best way to reamp tracks!

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