The first commercially available balanced headphone amp, which created the ultra-high-end headphone amp category. As J. Scull said in Stereophile: "the HeadRoom BlockHead was definitely close—real close—to the Orpheus, and reached, for me, total and absolute headphone reference quality." Also received the Positive Feedback Brutus Award. (both available on the web sites)
This is ultimate expression of the Blockhead ($3333 new), with the stepped attenuator option ($555 upgrade) and 2006 Max modules ($1400 upgrade, the most recent and final iteration). Totally dual mono, requiring two power cords and employing separate chassis joined only by front and back plates. Totally balanced (only XLR inputs).
I purchased this new in 2003 for $3,888, and upgraded to 2006 Max modules, which makes this the ultimate Blockhead -- every option, most current modules, single owner, basically mint except for a tiny ding on one corner (shown in pics). Includes original box and DiMarzio interconnects for cross-feed.
Only selling because the Audeze Edition sounds a bit better with my LCD-2 (at considerably higher cost). But if you have the Senn HD-600 or 650, you want the Blockhead.
Will throw in shipping and a pair of 6' PS Audio Micro Lab power cords at the asking price.