I purchased the headphone preamp. Listened to a variety of genres for a week on Sennheiser 800s cans. Compared the sound to my Bryston BHA-1, the headphone output on my Lynx Hilo and my Lynx Aurora. Not really a fair comparison, but it stood up well. Then, I did Bob’s suggested mod. Made quite a significant improvement! I’m going to use it as a portable preamp to take with me when I travel so I can get better sound from my laptop. What a bargain!