Palmer PBRIDGE4APLUS

Professional Multi-Function DI and Line Isolation in One Rack Unit

The Palmer BRIDGE 4A+ is a powerful, 4-channel active DI and line isolator in a rugged 19" rackmount format. It offers flexible input handling, transformer-isolated balanced XLR outputs, and three-stage signal boosting. With built-in Audio-over-Cat capability, this unit is ideal for studio, stage, and broadcast applications that demand reliability, noise-free performance, and efficient cable routing.

Palmer BRIDGE 4A+ Competitive Differences

• Multifunctional 4-channel design: use as DI box, line isolator, or signal booster
• Combo inputs support both balanced XLR and unbalanced 1/4" TRS connections
• Dual XLR outputs (front and rear) for each channel, transformer-balanced
• Adjustable gain in 6 dB, 12 dB, and 18 dB steps per channel
• Audio-over-Cat output for single-cable transmission of 4 audio channels
• Ground lift switches for eliminating ground loops and interference
• Operates on 9–18V DC with included external power supply

Palmer BRIDGE 4A+ Description

The BRIDGE 4A+ is an all-in-one signal management solution that adapts to virtually any live or studio scenario. Each of its four channels functions independently and can operate as a direct injection (DI) box, a line isolator to eliminate hum and noise, or a signal booster to compensate for long cable runs or weak instrument outputs. Each channel includes a combo XLR/jack input and transformer-isolated XLR outputs located on both front and rear panels, giving installers and engineers maximum flexibility.

This unit also features a unique three-step gain stage (6 dB, 12 dB, or 18 dB) that makes it especially useful in complex routing environments where precise signal matching is needed. The transformer isolation and ground lift switches on every channel protect against common audio issues such as ground loops and RF interference.

For even more efficient installations, the Audio-over-Cat (AoC) output lets you route all four channels through a single standard Cat cable (Cat5e or higher), significantly reducing stage clutter and setup time.

BRIDGE 4A+ Features

• 4-channel active DI, line isolator, and signal booster in one unit
• Combo input jacks for XLR and 1/4" TRS connections
• Dual transformer-balanced XLR outputs per channel (front and rear)
• 3-stage selectable gain: +6 dB, +12 dB, +18 dB
• Audio-over-Cat RJ45 output for all channels with ground lift
• Ground lift switch for eliminating hum and noise
• Steel 19" rackmount enclosure (1U height)
• External 9V–18V power supply included
• Power LED indicator

BRIDGE 4A+ Specifications

• Type: Active DI box / line isolator / booster
• Transformer Isolated: Yes
• Channels: 4
• Inputs: 4 x combo XLR/6.3 mm jack (balanced/unbalanced)
• Outputs: 4 x XLR (front & rear), RJ45 AoC
• Max Input Level: +16 dBu (1 kHz), +10 dBu (20 Hz)
• Max Output Level: +7 dBu
• Input Impedance: 20 kΩ
• Output Impedance: 84 Ω
• Frequency Response: 20 Hz – 20 kHz (±0.2 dB)
• THD + N: < 0.0023% (30 Hz), < 0.0009% (1 kHz)
• IMD (SMPTE): < 0.0018%
• SNR: 105 dB (unweighted, 22 kHz BW)
• Transformer Ratio: 10:1
• Power: 9–18V DC, 2W (external power supply included)
• Construction: Sheet steel, 1U rackmount
• Dimensions: 19" x 3.54" x 1.73" (482 x 90 x 44 mm)
• Weight: 4.63 lbs (2.1 kg)

Palmer PBRIDGE4APLUS (Palmer PAL-PBRIDGE4APLUS)