Just wanted to share short review and thoughts about the amp and cross feed.
I wanted a DAC amp for occasionally listening on my computer and something low cost because it is casual listening to me and I'm not paying attention to the music while on the computer. I'm also a sucker for DIY-like stuff so I got interested in Headstage amps that came cheap on Ebay:
Besides the price, what got me interested was also the cross feed option. The amp similar PA2V2 and Crossroads, using the same size Hammond case, but longer. Everything is fitted from the front because the 9V battery occupies the rear.
Workmanship is excellent and the volume control / power switch is extremely smooth, like those found on desktop amps. No scratching noise on the pot when adjusting the volume. Only cumbersome thing about this is that everything is fitted from the front. Thus it is almost impossible to have power, USB and headphone jack fitted at the same time.
Compared to the Hornet, the sound on this amp is neutral unless the bass boost is used. Bass is also not as punchy and deep to RSA's design and sound stage is not as wide. This is not really fair comparison of course but I don't have much to reference on.
Cross feed is interesting. It mixes the right and left channel slightly, much like how speakers work. It is subtle and noticeable. Tested with HD650 and K701, there will be a very slight drop in volume when cross feed is turned on. With well mastered recording like Norah Jones where instrument's volume is distinct and separate, it feels like vocals are in front of you while her musicians are playing around you on headphones. When cross feed is turned on, it sounds like you're sitting slightly further back, and Norah Jones' musicians have moved behind her.
The effect "feels like" a more narrow sound stage. I guess cross feeding creates the intended speaker effect and has less separation compared to headphones. However, it works pretty well for electronica music such as those from Orbital or Daft Punk. Some of these have electronic music that runs between the left and right channel and can be annoying / distraction during the left / right shifts. Cross feeding makes them sound much better and eliminates the channel shift distraction.
Overall, I thought it was pretty decent and cheap amp, with DAC. I don't like built-in Li-Ion amplifiers thus this works well for me. The cross feed feature is a hit or miss, depends a lot on how the source of the music was mastered.