Radial J+4 Balanced Signal Driver

Stereo preamp boosts signals to +4dB balanced line level
Radial J+4 Balanced Signal Driver


The Radial J+4 Balanced Signal Driver is a stereo preamplifier designed to accept unbalanced, low output devices such as instruments, computers, or CD players and boost the signal to a balanced +4dB level. 

The J+4 includes a variety of input connectors to accommodate most audio sources; a stereo pair of both 1/4" and RCAs, and a single 1/8" stereo input. The control panel is easy to operate, consisting only of a stereo level control, a high pass filter, and a ground lift. The boosted signal then outputs from a stereo pair of balanced XLRs. 

The J+4 features 100% discrete components for optimal signal transfer. Noise is eliminated by combining the advantages of active signal buffering with transformer isolation, resulting in better than 95dB signal to noise ratio. This also ensures hum and buzz caused by ground loops, along with spurious noise from clocking, will not pollute the signal path. 

The Radial J+4 is built to handle the extreme rigors of the professional audio world. It delivers exceptional sonic performance, plenty of headroom and ultra low noise making it the ideal addition to any audio system with low output sources.

  • Increases Gain for Low Output Sources
  • Boosts Signals to +4dB Line Level
  • Transformer-Balanced XLR Outputs
  • Versatile Inputs: RCA, 1/4 TRS, 1/8"

Boosts Signals to +4dB Balanced Line Level

 The J+4 takes a -10dB consumer level audio product, such as an iPod or a DJ mixer, and boosts the signal to +4dB commercial level without adding noise or distortion.
Versatile Input Options
 The J+4 has input connectivity for dual 1/4", dual RCA, and a single 1/8" stereo input.
Transformer Isolated
Transformer isolated circuitry eliminates noise caused by ground loops.


  • Circuit Type: Active -10 dB to +4 dB line converter, transformer isolated
  • Number of Channels: Stereo
  • Frequency Response: 20 Hz to 20,000 Hz (± 2 dB)
  • Dynamic Range: 102 dB
  • Maximum Input Level: +17 dBu @ 1 kHz, 1% THD+N
  • Total Harmonic Distortion: 0.004% @ 1 kHz, +10 dBu output
  • Phase Shift: 0.5° @ 100 Hz; 4° @ 20 Hz
  • Input Impedance: 10k Ohms, unbalanced
  • Output Impedance: 1.6k Ohms, balanced
  • Transformer: JS2 Radial custom transformer
  • HPF: -3 dB @ 100 Hz (12 dB/octave)
  • Lift: Disconnects XLR pin-1 at isolated output
  • Input Connections: 1/4" x2, RCA x2, 1/8" Stereo x1
  • Output Connections: XLR (pin-2 hot) x2
  • Construction: 14 gauge steel chassis & outer shell
  • Finish: Baked enamel
  • Power: Passive, no power required
  • Width: 84 mm
  • Height: 127 mm
  • Depth: 48 mm
  • Weight: 0.70 kg




  • Standard Delivery - Free
  • Express Delivery - $20
  • Store Pick Up (South Melbourne) - Free

Soundcorp will ship orders the first business day once all funds have cleared.


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