The Warm Audio Passive DI Box is an in-house development by the American manufacturer and is built using high-quality components around a custom transformer from CineMag USA. The strengths of this transformer clearly lie in its wide frequency response up to 70kHz and a rich tonal character, as is typical of CineMag products, for example in high-end microphone preamps. The design of the Passive DI is also impressive: the output pad circuit is adjustable from -3 to -30 dB, allowing for a more precise match to the signal source’s level than with any other DI box. Furthermore, the input can be set to power-amp level via a switch, so that it can be used directly between an amplifier and the speaker cabinet as a line out. In this configuration, the speaker or a load box must be connected to the ‘Thru’ socket.

When set to the ‘Lift’ position, the ground-lift switch provides what is known as a ‘soft ground’; this means that mains hum is filtered away to earth without having to interrupt the often vital protective earth connection.

• Transformers from CineMag USA
  
• High-quality, discrete components
• Circuit board with gold-plated traces
• Robust aluminium housing
• Branded sockets
• Input impedance: 1 MΩ
• Frequency response: 20 Hz – 70 kHz @ ±0.5 dB
• THD: 0.01% @ 20–100 Hz; <0.004% @ 100 Hz–20 kHz
• Attenuator switchable from -3 to -30 dB
• Input: unbalanced jack
• Switches for phase reversal and ground lift
• Outputs: Output (balanced XLR); Thru (unbalanced jack)
• Can be used directly on an amplifier’s speaker output with a load box
• Dimensions: 19 x 7 x 19 cm
• Weight: 700 g