I recently bought a CMOYBB kit from JDS Labs. I really only bought it for one reason and that's that I'm the kind of guy who needs to stay busy and likes hobby projects. I figured a CMOY would keep me occupied for a day or two and quite frankly I thought it was pretty cool. A headphone amp in a tin can, what's not to like? I really didn't expect much because first and foremost I'm a vacuum tube guy. My favorite headphone amp is a Bottlehead Crack w/ Sennheiser HD650's. Also I have a Bottlehead SEX amp in my office with Sony MDR-V6 which I swear could sound as good or better than the Crack rig. There's just something about the Sony MDR-V6 I really dig. Anyway this is about the CMOYBB......... I got the kit and soldered it up in one session in a couple hours. I've since built a second one and it took a fraction of that time. What slowed me down is there are no directions supplied in the kit. I had previously downloaded the assembly directions so I thought "No big deal". And it was no big deal until I got to step 2 (which is install C3+, C3-, and C4 capacitors). For the life of me I couldn't find the C4 installation location. And I noticed the directions I was reading didn't quite match the board I was working on. Must have been another revision. Went back to the JDS site and they had a pdf drawing of the Printed Circuit Board (PCB) which was identical and with that I was able to find the C4 location. I should also add this drawing and the actual board are pretty slick as positive and negative are generally marked on the boards, and direction of diodes is also indicated. Dummy proof! So I get that all figured out and it wasn't that hard and I pop a battery in and a source and a pair of Sony MDR-V6 headphones. I can't believe my first impressions. This little amp sounds amazing. I personally think it sounds almost as good, or as good than my Bottlehead Crack tube headphone amp with the Sennheisers. How the heck can this be? I go through my library of reference recordings. Tony Rice Unit, Stacey Kent, Norah Jones, Greatful Dead, Sarah Vaughn ............ WOW. I'm not easily impressed with gear but this kit has my attention. It has a bass boost function and after a lot of listening I decide it sounds great on some genres of music or at low volumes but it muddies things up if you are getting loud with modern pop music. So I mostly leave it off but it has a time and place. One other critical comment which has nothing to do with sound is the battery recharge circuit. It takes forever to charge a rechargeable 9v and the charge light never extinguishes (by design) so you don't know charge state. Maybe better to not implement the charger and just charge your 9v's off a proper charger. I love this little kit so much I ordered a second one and for fun put the first one up for sale on a local classified Facebook page. Sold instantly. I've since ordered a third one! I made a small blog page you can see here if you so desire..... http://www.hagensieker.com/styled-31/index.html .