Concert-2 Two channel direct box

299.99 Request

The Iso-Max Concert-2 is a stereo direct box designed to drive unbalanced instrument signals distances to 100 meters (300’) or more without high frequency loss or introducing noise into the signal path.

  • Converts unbalanced instrument signals to balanced mic level
  • Eliminates hum and buzz caused by ground loops
  • Ruler flat frequency response from 10 Hz to 100 kHz
  • Plug and play easy to use, no power required

The design begins with a rugged extruded aluminum enclosure and steel slide-in inner tray with recessed zones at each end to protect the switches and connectors. At one end, left and right ¼” instrument inputs and thru-puts are wired in parallel with a handy 3.5mm mini TRS for laptops and tablets. A -15dB pad decreases input sensitivity for greater signal handling when interfacing line level sources. At the other end, two XLR male outputs with ground lift makes for easy connection.

Inside, two high-performance Jensen JT-DB-EPC transformers provide galvanic isolation as they passively lower the impedance and perform the balancing. A high 140 kΩ input impedance reduces loading, enabling low-output instruments such as a vintage Fender® bass to be connected without losing tone. As hi-Z instruments are particularly sensitive to noise, internal Faraday shielding protects against interference from RF. An external MuMETAL® can further protects the sensitive internal workings to ensure a quiet interference-free performance even when surrounded by magnetic fields from amplifiers, power supplies and stage light dimmers.

With over +22 dB of signal handling capacity, the Concert-2 direct box gracefully handles extreme signals such as those produced by digital pianos while producing a warm Bessel response that is often referred to as ‘vintage’ sounding. These features combine to make the Concert-2 the ideal choice for studio or live use.


Concert-2 with stereo keyboard

The Concert-2 is designed for stereo devices like keyboards. Simple, straight ahead hookup makes it easy to connect your keys to your recording system for great stereo sound!

Concert-2 with drums & samplers

Driving the output from a sampler or electronic drum machine to the PA system has never been easier. The Concert-2 delivers plenty of headroom and lets you connect a local DJ mixer too.

Concert-2 with instruments

Two Jensen Concert-1 direct boxes in one, multi instrumentalists rejoice! The Concert-2 is perfectly well suited for bass, acoustic guitar or just about any instrument with a pickup.


Input impedance, Zi 1 kHz, 0 dBu, test circuit 1 48 kΩ 200 kΩ  
Voltage gain 1 kHz, 0 dBu, test circuit 1   -20 dB -35 dB
Magnitude response, ref 1 kHz 20 Hz, +4 dBu, test circuit 1 -0.25 dB -0.08 dB 0.0 dB
20 kHz, +4 dBu, test circuit 1 -0.25 dB -0.07 dB +0.1 dB
Deviation from linear phase (DLP) 20 Hz to 20 kHz, +4 dBu, test circuit 1  



Distortion (THD) 1 kHz, +4 dBu, test circuit 1   <0.001%  
20 Hz, +4 dBu, test circuit 1   0.036% 0.10%
Maximum 20 Hz input level 1% THD, test circuit 1 +19.5 dBu +21.5 dBu  

Input common mode rejection ratio (CMRR)

unbalanced source

60 Hz, test circuit 2   80 dB  
3 kHz, test circuit 2 40 dB 45 dB  
Output impedance, Zo 1 kHz, test circuit 1 135 Ω 142 Ω 155 Ω
Optimal cable length input*   3 m (10’) 15 m (50’)
output   30 m (100’) 150 m (500’)
Temperature range operation or storage






Frequency Response
Phase Shift vs Frequency
Total Harmonic Distortion vs Frequency
Total Harmonic Distortion vs Input

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