As mentioned above the stock sound was pretty bad, at least for my tastes- blues with some soul and rock. A good clean bluesy sound is a high priority for me since I can always add pedals to dirty it up a bit.
With the tube swap mentioned above and the Eminence Red, White and Blues, the sound wasn't too bad (I've played worse!) but I found it to be too dark and compressed for my own personal tastes. So I put on my Dr. Frankenstein lab coat and proceeded to do some surgery on this amp.
Some background: I really liked the Clean channel of the V33 when they were selling them in the stores last year. So I tracked down the schematics and layout drawings for both the V33 and the V18, and figured out how to morph my V18 into the Clean channel of the V33. In short, my game plan was to bypass the 2nd tube stage, and to swap in the components used for the V33 Clean channel. That was actually much easier than it sounds if you know how to work on printed circuit boards. I also did a few fine-tuning tweaks to make the amp sound more like the amps I really enjoy playing.
As for the reverb, I soldered a 33k resistor across the two terminals on the RCA jack connected to the output of the reverb tank, which brought the reverb down to a more reasonable level. (I also added a Dwell control.)
In any case with all of these mods- which would take a good amp tech maybe 3 hours to do- this amp is now a total monster for clean blues! I call it my poor man's Maz 18, and with a pedal or two it gets some great overdriven sounds as well. It should be noted that without a pedal it doesn't distort much at all- you can crank it all of the way up and it is still fairly clean. But if you really like the clean channel of the V33 or V50 that is basically what you get (although the extra Volume control can be handy, something which the Clean channel of the V33 and V50 lack).
My rating for Sound Quality is based on the V18 that I modded- I'd give it a 10 for the great clean sound, but will knock it down a bit since it doesn't dirty up when you dime the pre-gain.
The amp seemed to be made very well, with a plywood cabinet and well braced back panels. I have read many horror stories of the amps burning up almost immediately, more so with the V33 and V50. I figure that if it makes it through the first month, it should survive for a year or two. With the amp being shipped from China, the problem could partly be connectors that have come loose in transit so it probably would be a good idea to have someone qualified take the back panel off and inspect the circuit board before plugging it in for the first time. Or just send it back for an exchange or refund if it dies right away...
Out of the box I'd give this amp a 5. After replacing the tubes and speakers I'd give it a 6. After doing the mods I would give it a 9 since it has such a great clean sound. So I'll split the difference and give it an 8.
For more details on the mods send me an email. I will eventually write up the mods and put them on my website, www.blueguitar.org, along with some sound samples.
If you are not familiar with working on high voltage electronic circuits, perhaps you have a friend who could do the mods for you. (If you were to pay an tech amp for 3 or 4 hours labor plus materials, it would defeat the purpose of modding a $150 amp).
In terms of clean headroom my modded amp *smokes* the Fender Blues Junior... of course, you do get some nice overdriven sounds when you push the Blues Junior (which you don't get from the CLEAN V18- hey, that rhymes!) For my next project I may get a V50-112 and see how I could improve the OD channel, which could then be transferred into the V18 for some great OD sounds...