"Connect to a digital device to obtain a higher level of sound quality. Pure music line transformer."
From the 1989 Philips Premium Audio brochure:
Inheriting the design concept of output transformers adopted by LHH series, including the Philips professional CD player LHH2000, which has a good reputation in broadcasting stations. A dramatic improvement in sound quality has been achieved by connecting to digital devices such as the line balance transformerformer L300, CD player, and DCC, DAT, which further enhances sound quality and sound field.
By floating the ground line, you can reduce digital noise and improve the dynamic range of the signal. You can easily obtain one-rank sound quality while making the best use of your system.
In response to the "hotness of people pursuing an audio mind without it", the line transformer is built to eliminate digital noise.
Its Marantz brother is the Marantz DLT-1 digital line transformer