Meier Audio CORDA QUICKSTEP Portable Headphone Amplifier Silver Measures: 8.8 x 6.6 x 2.2 cm / Weight without battery: 115 gr./ Supply voltage: 6 .. (9) .. 15 Volts DC / Mean current uptake: 35 mA / 20mA (high/low-current-consumption-mode) Discrete volume control. Typical stepsize 1.5 dB, 31 steps. / Maximal amplification: -3 / 14 dB (low/high gain) / Active balanced headphone ground. / Star-grounding and ultra short signal paths. / Input impedance: 120 / 17 kOhm / Output impedance: &lt; 1 Ohm The unit runs from a single 9V battery and internally the supply voltage is used to create a pair of +4.5 and -4.5V powerlines (low current consumption mode) or a pair of +9 and -9V powerlines (high current consumption mode). External powersupplies can be connected with voltages between 6V and 15V DC. This supply voltage is internally doubled to create a pair of +6..+15V and -6..-15V powerlines. Noise is removed by extensive LC-filtering of the supply voltage. RF-noise (iPhone!!) is removed by extensive filtering of the input signal. The total buffer capacity is 4700 uF to lower the effective battery impedance. For amplification five single OPA209 opamps are used for maximal sonic performance.(No dual or quad-opamps!) The heavy-duty (!!) 3.5 mm sockets are gold-plated. Inside the signal path only metal-resistors and high-quality film-capacitors are used (polypropylene). The enclosure is made entirely of aluminium. Accessories: 2 mini-mini interconnects (goldplated) tool to open the amp