The high-end devices have a fully symmetrical layout for operation with analogue audio sources, thus ensuring absolutely symmetrical signal transmission from the source to the headphones.

ENGADGET: Sennheiser unveils HDVA 600 analog headphone amp, asks for $1,600

That means that not only the signal input into the amplifier is symmetrical but also the signal output and therefore the connection to the headphones.

ENGADGET: Sennheiser unveils HDVA 600 analog headphone amp, asks for $1,600

Signal processing in the HiFi devices is fully symmetrical.

ENGADGET: Sennheiser unveils HDVA 600 analog headphone amp, asks for $1,600

Yamaha designed the model with left-right symmetrical audio circuitry to provide the shortest circuit path for audio signal travel without loss of audio signal purity.

ENGADGET: Yamaha's CD-N500 network CD player comes to the States, priced at $800