The recent positive reviews of the Pass Labs HPA-1 headamp made me think ... I have a Pass Aleph 5 DIY that my brother built for me almost 10 years ago. And it remains my reference for absolute musicality ... truly the most involving and emotionally gripping amp I have ever heard, bar none. Silky but revealing, dynamic but subtle. Those contradictory qualities that seemingly only the very best can balance. I've considered selling it several times but I will probably leave it to my kids who will donate to hospice. It would be incredible to have the Pass signature sound in a headphone amp. And while the $3500 HPA-1 is clearly an unattainable dream I was wondering if some of that Nelson Pass magic could be heard on cans for less money .... and then I stumbled across this! http://www.6moons.com/audioreviews/realitycheck1/aben.html It is an adaptation of an Aleph Mini for headphone service! The Aleph Mini itself is a down-sized of the Aleph 3. Explains Terry Aben: Quote "My headphone amp, which I have dubbed the Aleph H, is simply a scaled-down version of Nelson Pass' Aleph amplifier series. Nelson Pass has made the unbelievably generous donation to the DIY world of making public the service manuals to all of his designs once they are out of production - and he actively participates online on the Pass Labs Forum at DIY Audio helping hobbyists like myself with our creations. Nelson's single requirement is that we restrict the use of his intellectual property to the creation of products for our own personal use. If you want to contact me looking to buy an Aleph H, go ahead but be aware that I'll have to make some sort of licensing arrangement with Mr. Pass first, assuming of course that he's amenable to the idea. The Aleph H circuit topology is identical to a Pass Aleph 3 with the exception of substituting a pair of lower power IRF610 MOSFET transistors for the 4 larger IRF244s and adjusting several resistor values to set the proper operating parameters of voltage and bias within the circuit. The Aleph H swings a maximum output of 14V and 0.5A compared to the Aleph 3's stats of 23V and 8A. I must also point out that like most DIYers, I had some help along the way of creating this amplifier. First, Marcello Pellerano modified the Pass Zen amplifier to create a Zen headphone amp, which he documented at headwize.com and diyaudio.com. Also, 'Grey' Rollins from diyaudio.com created a scaled-down version of the Aleph amplifier, which he called the mini-A intended as a low-wattage speaker amplifier. Next, jwb from diyaudio.com modified the Aleph circuit to produce a headphone amplifier that substituted JFETs for the MOSFETs in the input stage. I studied these design extensively in preparing for my amplifier. Wow ... this may just be the ticket! The boards are sold on eBay for under $10 and the rest of the components should be easy to come by. I'm not very handy but my brother is. Before I coerce him into another Pass build project, has anyone had any experience with either the Zen or Aleph Mini headphone amps?