United Studio Technologies Replay Box

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An easy to use Reamping device with dual transformers to deliver a clean and quiet signal!

The best re-amp box. The debate is finally over.

United’s Replay Box offers the very best performance and options for re-amplification. Whether you’re producing the most tone-savvy musician or experimenting with sound design, the Replay Box performs on a level all of its own — with an ultra-quiet design and flexible tone voicing.

With two different custom transformers for two unique sonic fingerprints and all of the gain you need, the Replay Box raises the bar for all recordists.

Two transformers for two different voicings.

Replay Box features two independent reamplification circuits: Transparent and Harmonic.

The Transparent circuit features our custom-wound, US-made, 5043 step up transformer, which provides extraordinary signal isolation and noise rejection for mastering-grade quality. It accepts your balanced or unbalanced line level input signal to deliver an absolutely clean, isolated, unbalanced output capable of driving any amp, pedal, or processor. Because the transformer is wound to have passive gain, it has about 3 dB of additional gain on tap above its already +4 dB rated input from your DAW or recorder. No active circuitry or other components are involved — you get the cleanest gain available on any re-amplification device.

The Harmonic circuit is for those who desire a bit more coloration or fattening in the re-amp stage. Harmonic mode engages an alternate transformer specifically designed to add character. This transformer is wound to offer a steeper gain ratio alongside a very gentle rolling-off of the uppermost high frequencies. It adds both harmonic and phase distortion in the sub-bass region, fattening the low mids and delivering a more aggressive and warmer tone.

All the pure transformer gain you could ever want for re-amping.

The Replay Box was designed from the ground up to solve the two most common problems found in re-amping: noise and low gain.

When re-amping, any and all unwanted noise is re-amplified alongside the desired musical content. Unfortunately, most re-amp boxes on the market add some degree of noise and coloration to the signal, making it harder to achieve a satisfying result. Furthermore, most re-amp boxes also do not provide enough gain to drive an amp well, meaning engineers need to rely on boost or preamp pedals… which in turn add additional noise, distortion, and unwanted character.

We designed the Replay Box to provide more clean gain than you’ll ever need, without ever needing to add a noise-inducing preamp or boost pedal. And its true ground isolation further ensures you won’t be plagued by ground-loop hum while re-amping.

Industry-proven before launch day.

Until now, this dual-transformer design was never commercially available, and only existed in the hands of a few. Replay Box is the culmination of two decades of experimentation and user feedback from early adopters of Chad Kelly’s early hand-made reamplification boxes. These early units became the secret weapons of top industry engineers the world over… and over the years, their insights refined the design.

Outside of its fantastic internal design, the Replay Box also sports an aluminum chassis that’s built not only for the rigors of the road, but for facing hard-to-impress studio clientele. Its recessed design protects from both studio accidents and on-stage flying kicks, while its screw-mounted removable feet add options for creative mounting when necessary.

With over 50 years of combined industry experience, we at United have spent years on the research and development of Replay Box to offer you the two most respected, boutique re-amp products in a single enclosure.


  • Input impedance: 300 Ω, harmonic mode: 50 Ω
  • Output impedance: 1k Ω, harmonic mode: 150 Ω
  • Frequency response: 20 hZ-20 KhZ +/-0.5dB, harmonic mode: 40 hZ-20 KhZ +/-0.5 dB
  • Input: recommended +4 line level balanced input
  • Output: max +3 dB above input level, harmonic mode: +5 dB above input level
Our ONE WITH EVERYTHING ZEN WARRANTY extends the standard manufacturer warranty by one year, see our ZEN WARRANTY page for details.

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