All:
I just added the following to this review:
UPDATE 4-1-08 - "White" Headphone Amp/USB DAC
David sent me the "White" to test. This is his "premium" product (so far anyway) - it's the same size as the others, but includes a different feature set:
> Has both line input AND USB DAC input, with switch
> Stepped Attenuator
> High/Low gain switch
> No speaker outputs
Pic:
The "White" amp shares the same basic sonic signature as the others - quick and fast, but is a little lusher in the mids than the Red and Green amps are. The treble is also smoother, while being just as extended. The bass is maybe just a tiny bit tighter, with perhaps just a tiny bit less quantity in the bass.
The "White" is even more transparent sounding than the Red and Green, which I feel are fairly transparent to begin with. The White actually is remarkably transparent. It also has a LOT of drive capability - even in low gain, I only needed setting 3 on the stepped attenuator to get all the level out of my Denon D5000 that I could possibly want. I don't listen super-loud, but the D5000's aren't the easiest headphone in the world to drive. No problem driving my 600 ohm Beyer DT990's, either.
For $290, it isn't the crazy screaming bargain that the Red is, but it offers highly competitive sound. For me, the $100 more for the White is EASILY worth the improvements in smoothness and the slightly more lush midband. I continue to be impressed with David Lin's products.