React : IR - Reactive loadbox with IR loader and attenuator

React:IR – is a reactive-resonance load box, attenuator and impulse loader with length up to 190 ms.


What do “reactive”, and “resonance” mean, and why is it important?  


Let`s figure it out, what means reactive, resonance and why it`s important…


   Valve (tube) guitar amplifiers have relatively large output impedance due to the output transformer. The guitar cabinet represents a complex reactive load to the amplifier and drastically affects the frequency characteristic of output signal. Adding to this, the majority of guitar amplifiers have negative feedback. This means that some part of output signal returns again to the input of the power amplifier and mixes with the main signal.


  Thus, when we speak about a load box, it's important to understand principles of the device's operation and its influence on signal. Guitar speaker manufacturers often publish the impedance curves of their respective products. Usually, guitar speaker have their largest impedance at lower frequencies around 70-90 Hz.    When inside a cabinet, the peak at low frequencies resides slightly higher, for example, in 4x12 cabinet, the peak is located around 100-115 Hz due to the cabinet construction. Thus it's important to reproduce not only speaker characteristics, but also the characteristics of the entire cabinet.

  1. Power switch

  2. Headphones output

  3. Auxillary input for connecting external sources like players, smartphones etc.

  4. Headphones volume

  5. Impulse loader input level

  6. 5-segment input indicator, for optimal result adjust input level to be in yellow/orange zone, not exceeding red segment.

  7. Main screen

  8. Output clipping/input signal presence indicator. When Clip indicator lit green, signal is present at input, when clipping occurs at output of impulse loader, indicator switches to red.

  9. Menu button, press to enter menu.

  10. Back button, press to return to previous menu level.

  11. Control dial. Rotate to navigate or change parameter, press to select or set.

  12. Attenuator level

  13. Resonance switch

  14. Load mode switch

  15. Fan, do not block air flow for proper ventilation.

  1. Through output for cabinet connection, when jack inserted, internal load and attenuator are disconected. Careful with amp level, when switching to this output.
  2. Input for power amplifier output. Reactive load is suitable for impedance of 8 Ohm with nominal power of 100 Watt.
  3. Attenuator output
  4. Line input/load box output, jack tip is line input for external signal sources for IR loader, jack ring is load box output for connection to external FX devices. When mono jack is inserted connector works as line input, disconnecting IR loader from load box.
  5. Ground Lift switch for D.I. OUT, useful for solving ground loops problems.
  6. D.I. output allows recording raw signal from load or cabinet before impulse loader section. Output is balanced and can be powered from phantom power.
  7. Ground Lift switch for LINE OUT
  8. Balanced line output for recording signal after impulse loader section.
  9. Pad switch for LINE OUT, serve for output level reduction to microphone level.
  10. USB connector for remote control from PC/MAC and impulse response uploading to device.
  11. MIDI In connector for preset switching from MIDI.
  12. Power supply connector, use 7-12 V DC power supply with any polarity.
  13. S/PDIF Out.

 Historically, different equipment manufacturers have produced different types of load boxes. Initially, a simple passive type of load is used. Then, reactive types were introduced. However, the term, “reactive”, can refer to only high frequency component without low frequency component. Thus, the term, "reactive-resonance”, load was introduced which means correction not only of high frequencies, but also low frequencies. The graph below represents the influence of different load types on frequency characteristics of signal.


    React:IR allows usage of all three regimes: passive, reactive and reactive-resonance. The respective modes can be set using switches in the Loadbox section on the front panel of the device.In addition, the device has attenuator, which allows the usage of an amplifier at maximum volume, while listening at quiet “TV” loudness.


   React:IR has a number of FX-effects:


  • Noise Gate
  • Tone stack - amplifier Tone Stack emulation with several models of popular amps
  • PA Curve – amplifier-cabinet interaction curve
  • 5-band paragraphic equalizer with high cut and low cut filters (LowPass and HighPass)


Tone Stack emulation can be used in when running a distortion stompbox directly into the line input, for emulation of frequency response of guitar amplifier clean channel.

Impedance Curve emulation can be used for guitar preamp connection into line input, in this case frequency response modified to emulate connection trough guitar power amp.

ADC and DAC characteristics:


  • Sampling frequency up to 192 kHz
  • Resolution: 24 bits
  • Noise level : -109 dB (A-weighted)


DSP-engine characteristics:


  • Measured latency 1.3 ms
  • 32 bit floating point, 44.1 kHz
  • Internal impulse format:  44.1kHz, 32 bits, maximum length 8448 samples
  • 25 impulse slots/preset


Power supply:


  • 9 V DC, any polarity
  • Consumption: up to 250 mA.

Download latest software bundle :






      Include versions for Win32, Win64, MacOS and Firmware

Dimensions & weight


  • Width x depth x height: 483 x 187 x 44 (mm)
  • Weight: 3 kg (device only )

Equipment and packaging


  • 1 x React:IR 
  • 1 x Power Supply
  • Packing size 60x29x8cm 
  • Packing weigh 3.8kg

Reactive loadbox


Input impedance : 8 Ohms
Admissible power : 100W RMS



  • Speaker Input: 1/4″ (6.35mm)Jack unbalanced (TS, Tip/Sleeve)
  • Speaker Thru: 1/4″ (6.35mm)Jack unbalanced (TS) – Directly connected to Speaker Input. Disconnects the loadbox when used.
  • Insert: 1/4″ (6.35mm)Jack unbalanced (TS, Tip/Sleeve) in insert mode or (TRS, Tip/Ring/Sleeve) in insert\out mode.
  • D.I. Balanced Output:  XLR.
  • Main Balanced Output:  XLR.
  • Headphones: 1/8″ (3.5mm) TRS Jack
  • Aux In: 1/8″ (3.5mm) TRS Jack
  • S/PDIF output - RCA Connector - Sampling frequency 44.1 kHz. Resolution 24 bits.
  • MIDI input - DIN5 Connector

Block diagram