Benchmark HPA-2 Audiophile grade stereo headphone amplifier

* INPUT: Stereo 200 K ohm Balanced Inputs * INPUT CLIP: = +26.5 dBu with ±15 volt supplies * OUTPUT: Stereo, for use with 1/4" Tip/Ring/Sleeve plugs ONLY, other panel connectors may be wired to the amplifier by way of on-board output connectors * OUTPUT Z: "0 ?" * OUTPUT CLIP: Dependant upon power voltage and load [+20 dBu @ ±15V and 60 ? load] * LOAD Z: 30 ? or higher * OUTPUT LEVEL: up to +20 dBu into 60 ? [dependent upon power source] * OUTPUT CONTROL: Dual log taper response * GAIN RANGE: off to +20 dB * BANDWIDTH: 0.1 Hz to 300 kHz minimum * THD+N at headphone inputs: 0.0003% typical - under load! * NOISE FLOOR: Better than -75 dBu at maximum gain * POWER: (Bipolar) ± 9 to ± 18 volts, maximum peak current needed = 1.1 Amp at maximum peak output into 30 ? * Peak output power = 7.5 watts [±18 volt supplies. 30 ? load] * Maximum average audio output power [-8 dB peak to average ratio] = 1.35 watts * Volume control knob included PHYSICAL: Amplifier PCB: length behind panel = 3.760", width = 1.335", mounting hole diameter = 0.437" [7/16"] Volume control PCB: length behind panel = 1.025", width = 1.335", mounting hole diameter = 0.275" [J drill or 9/32 (0.281)], shaft length = 0.385", shaft diameter. = 0.235" [16-star spline]. Minimum spacing between potentiometer PCB mounting hole and 1/4" jack = 7.5", Minimum spacing between amplifier PCB and volume control PCB = 0.75" [both PCBs mounted vertically], Maximum panel thickness = 0.1". Knob diameter = 0.75", length = 0.75". Recommended headphones: Sennheiser HD600.