React : IR - Reactive loadbox with IR loader and attenuator

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


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


   Valve guitar amplifier has relatively large output impedance due to output transformer. Guitar cabinet represents complex reactive load to amplifier and drastically affects frequency characteristic of output signal. Besides, majority of guitar amplifiers have negative feedback, this means that some part of output signal comes again to input of power amplifier and mixes with main signal.


  Thus, when we speak about load box, it`s important to understand principles of device operation and its influence on signal.Guitar speaker manufacturers publish impedance curves of their respective products. Usually, guitar speaker have largest impedance at lower frequencies around 70-90 Hz.    In real cabinet peak at low frequencies resides slightly higher, for example, in 4x12 cabinet, peak is located around 100-115 Hz due to cabinet construction. Thus it`s important to reproduce not only speaker characteristics, but characteristics of 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 for external signal sources for IR loader, when jack is connected to this input, signal from load box is disconnected.
  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.


    Historically, different equipment manufacturers produce different types of load box. Initially simple passive type of load is used, then reactive types were introduced, but term reactive can mean only high frequency component without low frequency component. Thus term reactive-resonance load was introduced which means correction not only of high frequencies, but also low frequencies. Graph below represents influence of different load types on frequency characteristics of signal.


    React:IR allows usage of all three regimes: passive, reactive and reactive-resonance. Respective mode can be set using switches in Loadbox section on front panel of device.

In addition, device has attenuator, which allows usage of amplifier at maximum volume at quiet “TV” loudness.


   React:IR have 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 case of some distortion stompbox into 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:


  • Latency: 1.2 msec
  • 32 bit floating point, 44.1 kHz
  • Internal impulse format:  44.1kHz, 32 bits, maximum length 8448 samples
  • 25 impulse slots/preset


Power supply:


  • 7-12 V DC, any polarity
  • Consumption: up to 200 mA.