Active 48V DI Box with Custom Isolation Transformer

UNiKA PRO-148 is a professional Active DI box designed to match electric and electro-acoustic guitars, basses, effects pedals and other high impedance sources to the balanced microphone inputs of a mixing console or external mic preamp. As PRO-148 uses the mic preamp’s 48V phantom power, no batteries or other power supplies are required.

UNiKA PRO’s specially-selected induction transformer, separate custom audio isolation transformer and high (260kOhm) input impedance combine to ensure a bright, open, exceptionally musical sound, rich in harmonics.

UNiKA PRO-148 is equally at home on stage or in the studio with a rugged steel casing, full-length anti-slip mat and recessed connectors.

INPUT — XLR + TRS Combo allows the connection of a wide variety of unbalanced and balanced sources to the PRO-148.  Normally these would be high impedance signals from instrument pickups but PRO-148 can also be used as an ISO for line level signals to prevent hum and interference.

PAD Switch — reduces the input level by 20dB to prevent distortion from high level signals.

PAD LED — illuminates when pad is IN.

THRU — connects the PRO-148 to an instrument amplifier.

ISO OUT XLR — connects the transformer-balanced low impedance audio signal to the microphone pre-amp using a standard mic cable. It also connects the PRO-148 to the mic preamp phantom power supply.

GND/LIFT — Breaks the ground at the output of the transformer to eliminate hum and noise caused by ground loops.

+48V ACTIVE — illuminates when 48V power is present to assist fault finding.

Rugged Steel Chassis —with Anti-Scratch Paint.

Anti-Slip Mat — full-length, flexible plastic pad cushions and stabilises the PRO-148.

System Specifications

  • Circuit Principle: Active with Transformer Balanced Output
  • Input Connector: 1 X XLR+TRS Combo Jack
  • Link Connector: 1 X TRS Jack
  • Input Attenuator and Indicator: 0/-20dB push button + LED
  • Power Supply: +48V phantom power supplied through the output terminal with LED power Indicator
  • Output Terminal: XLR Male socket through balancing ISO transformer
  • Output GND/LIFT switch: Push button
  • Input Impedance: 260 kOhm/0dB, 50 kOhm/-20dB
  • Output Impedance: 50 Ohm
  • Maximum Input Level before clipping: +10dB
  • Maximum Output Level: +10dB
  • Frequency Response: 20Hz-20kHz, 0.3/+0.6dB
  • S/N Ratio @20Hz-20kHz un-weighted: Greater than 95dB
  • T.H.D @1kHz 0dBV Output: Less than 0.02%
  • Type of ISO Transformer: 1+1:1+1
  • Chassis: 1.6mm/1.2mm steel
  • Finish: Anti-scratch paint
  • Dimension (W X D X H): 78 X 124 X 46mm
  • Unit Weight: 0,56 kg


Est. 1985. Strictly Confidential...

UNiKA has manufactured high-quality audio products for internationally-respected brands for over 35 years. So you may already own, love, and depend on a quality product proudly-designed and built in Taiwan by UNiKA. We would love to name names but as we have promised confidentiality our lips are sealed!

We have a passion for great-sounding gear. So we decided to start our own brand to give our team the freedom to build and market their exceptional designs. Enter UNiKA Pro!

That was 2018 and there is now a comprehensive range of top-spec Dante I/O interfaces—the NBB Series—and an entry-level range of budget DI's—the Stage Series. Go check them out! Based on customer feedback, dealers and distributors asked us to make a flagship DI series with the emphasis on musicality but without a boutique price-tag. So how did we do this? It started with the transformer….

At the heart of the PRO-148 and PRO-248 is the UNiKA EI30A10E 1+1:1+1 audio isolation transformer. This is a bespoke design with a special copper foil layer and dedicated grounding layer. It has been specially-selected to enhance musicality by producing a sound rich in harmonics.

Grounding interference and leakage caused by potential differences are minimised and low impedance balanced outputs allow long cable runs with the very best audio quality.

A separate induction transformer powers the active circuitry in the PRO-148 and PRO-248. This is the trusted, high quality OEP PT-4 unit, made in the UK.  Combining this with the isolation transformer extends the flexibility and performance of the PRO-148 and PRO-248 over induction-transformer-only, active designs.

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