Pros: Beautiful to look at, D.I.Y is fun, crisp sound, transparent, soundstage
Cons: D.I.Y can be daunting to some, accurate bass might be a downside for some, no tube rolling, tube hum
Dat Sweet tube glow
NOTE: This is my first real amp. I had a Fiio E11 prior to this, but this is my first real step into the hifi world.
This amp is a pleasure to listen to and build. I wasn't sure how daunting the task would be because I have little electrical experience (The last time I used a soldering iron was a robotics class I took in 7th grade). My build time was approximately 16 hours over 3 days. I have the C4S kit but I have not installed it yet. The amp is pretty simple to build and the instructions that are supplied with the kit are very good. The only thing about the build that is really difficult is wire organization. I didn't care too much for wiring but I assume if you're a neat person it'll save you a little trouble with the electrical components.
I haven't burned the amp in completely I only put a few hours onto it so far, but it sounds amazing. The vocals are really brought forward with this amp and the staging of the sound is incredible. As far as reference tracks I listened to the Richie Blackmore's Rainbow album and the acoustic guitars sounded like they were right in the room and the voice of Dio was just pushed to a new level for me. I listened to some difficult tracks too. Self vs. Self by Pendulum has always been a trouble track for me because as a death metal/drum and bass hybrid song I found nothing did it justice before; car and computer speakers wouldn't cut it. However I feel like everything is really brought forward by the S.E.X and it really makes the song a pleasure to listen to. Another difficult track was Some Might Say by Oasis. This song has so much gain in it I felt like it sounded like a beehive most of the time, but the S.E.X really cleared it up and allows it to sound natural and spacy.
Overall I think the S.E.X amp is fantastic for vocal tracks and it supplies a good amount of bass that is very accurate but not overwhelming.
There is a bit of hiss from the amp. It isn't very noisy but it is audible when no music is playing. I imagine installing the C4S upgrade will improve the blackness for the noise background.
EDIT: I recently upgraded my DAC to a Fiio D03K over optical from my computer and the hiss is gone. I think it was just the cheap DAC I was using before that was making the noise. The amp is COMPLETELY BLACK in background noise. I can't hear any audible hiss until I turn the knob to 90% but I amp playing everything at less than a quarter turn.
Unfortunately I don't have anything to compare the amp to besides my Fiio E11 but this is obviously classes above that. But, I think this really is a world class amp and anyone looking for a beginner DIY project or high quality amp should strongly consider the S.E.X amp.
Here are some pics of my sloppy work