The Stax SRD-7 operates differently from a traditional Stax amplifier. It must be connected to a standard speaker amplifier, from which it draws power and converts it into the high voltage required to drive Stax electrostatic headphones.

It remains a popular choice among Stax users as it provides a more affordable alternative to dedicated electrostatic amplifiers.

The SRD-7 shown here is a normal bias version, with both headphone outputs using 6-pin Stax connectors compatible with normal bias headphones. There are also professional bias versions of the SRD-7, designed to work with higher-bias Stax headphones.

The unit is fairly compact, measuring approximately 12 cm x 7 cm x 20 cm, and fits easily into most setups. The front panel features a switch to turn the unit on and off. When the switch is in the off position, the signal from your amplifier is routed to your speakers, allowing you to easily switch between headphone and speaker listening.

Sold with the exceptional, fully restored Stax SR-Σ panoramic electrostatic collector headphone — a true STAX listening legend.