The Hansen board is for a great little amp using two dual 2134 or equivalent opamps. The first is for gain and the second is for current. These are separated by a single or dual crossfeed section. This amp uses a resistive divider which can easily be changed to the TLE 2426 ground driver. Loaded with high quality parts, this amp sounds amazing and can be powered by one or two 9V and fits perfectly in the Pactec enclosure. 9VB available as a single or dual 9V configuration. Giving a professional quality look and performance to the DIY headphone amp.
This amp can be built with or without crossfeed. I finished my last on with all the crossfeed caps in place but no switches for it as yet. Dual crosfeed requires a triple pole triple throw switch and I only have triple pole dual throw switches. I might just activate the bass enhanced crossfeed, but actually don't care for crossfeed at all.
This amp will cost probably around 80.00 to 100.00 for the best parts (or better parts) depending on your reference, but the amp will be IMO a Reference amp when completed with high Q parts. Mine is built with 2132 opamps, Vishay resistors matched to .1% Cerafine Caps for Power supply, Panasonic pot. Panasonic metal films for crossfeed (unused), and .999 fine braided silver wire for all connections with the dual 9V pactec box and Gold RCA inputs with gold 1/4" output. This makes for an exceptional portable amp I wouldn't sell for 300.00. This amp sounds incredible.