Friday, June 14, 2019

"retro-2308" - portable chip headphone amp

I have been using the Oatley K272C kit in a portable HP amp enclosure for years now. It has spent a lot of time on trains, planes and overseas. Also good use when the wife is home on weekends. After building “LeManja” I realised how good the PT2308 dedicated HP driver chip was. Feeling the K272C a little on the large and heavy side for traveling I figured I could build a smaller lighter portable amp. I wanted to retain the high performance I have been use to in the past.

Above is that build which runs on four AAA batteries for over 100hours of play. That is with cheap AAAs. With lithium’s you could double that time. The enclosure is two tone ABS with matching knob. Al lining is used on the bottom and top of the enclosure and is earthed. The amp is built on Vera-board and is extremely compact. I didn't have much room in the enclosure for the cct. brd.

All caps are NP or LESR and all hookup wiring is silver plated fine copper wire. Safe on is provide with a switched input phone socket. If there is no plug in the input socket the amp will not run. There is also an off switch. The chip is the PT2308 (Class AB) with a THD of 0.001%. The sound is solid and crisp and drives both 250ohm and 32ohm HPs with ease. Light, compact, extended battery life and great sounding. Just what I wanted.