Valve Headphone amp for HD600.

I use the Little Dot MkII, but I removed the foam on the HD600s. With a SuperPro 707 getting its digital input via USB (so it also gets 5v for the DAC, and the analog opamps get the powerbrick to themselves), I barely get to 9:00 on the dial, and that's with Media Monkey preamp turned down to -10db. And besides being able to drive the HD600's to ear-shattering levels, it actually sounds good. highs are smoothly rolled off, no fatiguing spikes in the treble, mids and bass have impact and are nicely integrated.

You can order through the company's website, or through eBay.

http://www.littledot.net/forum/index.php

I have both a Cayin HA-1A and a ASL MG Head DT/OTL MKlll.  Both have vintage tubes installed.  I prefer the MG Head ( in the OTL mode) over the much more expensive Cayin for use with my HD600's. It warms up and moves the midrange a bit more forward, and just sounds more involving. Of course, it's a well documented good match here at Head-Fi.  The Cayin is likely a less colored presentation, and very smooth, but lacks the tube "fat sound" I prefer. I do for the record have a pair of AKG-701 and Sony MDR-CD3000 which both sound excellent with the Cayin.  Since the Cayin has selectable impedance settings, this allows an excellent match with many headphones. One down side on the MG Head is that they have had some quality control issues.  One of the two LED pilot lights on mine went out in the first few minutes I had it. And upon checking the guts for assembly quality, I found some sloppy soldering. Still, I have had mine for many years and  would recommend it highly.