Wednesday, January 2, 2013
Chip based headphone amp
Based on the high performance OPA2134 OPamp chip this headphone amp\driver is good sounding and portable. The schematic is based on the CMoy design with some changes in passive parts values. I elected to run it on two 9V batteries for better battery life and greater dynamics.
There is only 4" total of hookup wire in the signal path and all component-2-component connections on the proto cct. brd. Low ESR 200uf caps and a resistive network provide the differential voltages required to operate the chip without an output cap. The brd. is silver soldered with Mil.spec machined chip socket and Russian PIO caps on the input. Power only comes on when both phone jacks have plugs in them and the power switch (at the back) is on.The enclosure is impact resistant and lined with heavy Al foil for shielding and enclosure resonance control. The sound is clean and bright with good volume and dynamics. The amp is dead quiet with no signal.