I wanted to share the photos with you available on the link above courtesy of Graeme, Ian and Keith. For more information visit Ian's site http://www.leonaudio.biz and obtain the pdf where you'll find Cohen's papers and original OM1556 documents. Thanks guys.OK, it has taken quite a while, but my AES colleague Ian DuRieu has talked Graeme Cohen into presenting his perspective of the preamp that is the subject of this thread. It can be found here http://leonaudio.biz/cohen.htm Thanks Ian and Graeme, enjoy!
Keith Taylor
Here are the pics. Too bad we can't make hybrids at home.
The LM194 input transistors on the OM1556. Image courtesy of Graeme Cohen and Ian DuRieu.
An overview of the OM1556. Image courtesy of Graeme Cohen and Ian DuRieu.
A closeup of the OM1556. Image courtesy of Graeme Cohen and Ian DuRieu.
OM1556 Preconformal coating. Image courtesy of Graeme Cohen and Ian DuRieu.
OM1556 Conformal coating. Image courtesy of Graeme Cohen and Ian DuRieu.
An OM1556 Preamp. Image courtesy of Graeme Cohen and Ian DuRieu.
A "serious" Graeme Cohen in his workshop July 2008. Image courtesy of Graeme Cohen and Ian DuRieu.