The SRD-7 Adaptor for electrostatic Ear speakers raises the signal volrage to the level needed for ear speakers by means of a step-up transformer and provides the polarizing voltage necessary for the diaphragm with a power supply circuit. Along with the standard bias power supply circuit the SRD-7 also posseses a high bias power supply circuit for greater resolution and additional performance capabilities to match the Professional Series Earspeakers. There are two Earspeakers outlets: the NORMAL plug is for the SR Lambda Series Ac 230V. and other Series PRO ONLY modern series SE 500, SE 700. Ac.580 V Bias NORM. 230V DC conect 6 pini Bias PRO. 580V DC conect 5 pini The SRD-7 Adaptor is also avaiable equipment with PRO online earspeaker bias 580V DC 5 pini. Amplifier max continus power 8 watt. Headphones STAX SE 507 are not subject to this tender. The type of headphones SE 507 and SE 700 works with this amplifier. Instantaneous Max. input 30W ( 1kHz) Frequence Response. 10Hz- 30kHz. Distortion. Less than 0.02% Power Source 117-240V / 50- 60Hz Ac Bias Voltage 580 V only Professional Power Consumption 0.1 W Dimensions: 73×120×215mm Weight. 1.7 kg.