Meier Audio CORDA PCSTEP USB-DAC Portable Headphone Amplifier Silver Measures: 8.9 x 6.6 x 2.2 cm / Weight without battery: 115 gr. / Supply voltage: 6 .. (9) .. 15 Volts DC / Mean current uptake: 28 mA Discrete volume control. Typical stepsize 1.5 dB, 31 steps. / Maximal amplification: -2 / 14 dB (low/high gain) / Input impedance: 120 / 19 kOhm / Output impedance: &lt; 1 Ohm The unit runs from a single 9V battery, 5V USB-power, or an external powersupply (with upto 15V). Internally the supply voltage is doubled to increase driving capacity. External noise is removed by extensive LC-filtering of the supply voltage. The total buffer capacity is 1700 uF to lower the effective battery impedance. For amplification two single OPA209 opamps are used for maximal sonic performance.(No dual or quad-opamps!) The USB-DAC is based on the PCM2702 DAC-chip by Burr-Brown. / Resolution USB: 16 bit / Sampling frequencies USB: 32, 44, 48 kHz / The 3.5 mm sockets are silver-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) ,USB-cable ,tool to open the amp