Sun Valley vs Sun Audio 300b

Hey O, 

I just completed the Sunvalley 300b and had a great time doing it. Granted I did it twice since I misinterpreted a couple of basic instructions and my first attempt started to smoke after about 10 minutes of play. That said I'm not a pro, so chalk it up to rookie mistakes. I'd done probably six solid state FirstWatt amps prior to this, plus one SPUD tube amp, but this one was a little more complicated. 

The instructions, especially the illustrations, are very good, but the brief text explanations are aren't always the clearest (translation issues). Suffice to say you should pay close attention to the schematic and the images, particularly the icons in the process steps. Example: the lack of a red dot means "insert the component leads but don't solder yet", while a red dot means "insert component leads and solder now". Also there's a little red arrow that means "even though there are multiple leads soldered to this one lug, don't let the leads touch each other". 

Anyway, after my initial failure I realized I'd rushed at some important points, so I decided to desolder the whole thing and start over. I kept the caps, ordered some higher quality resistors, and got better wire since the hookup wire supplied with the kit is pretty cheap and you don't get a lot of it (though I'm sure it works fine). The silicone-covered 22awg I bought is not only a little thicker, it's more elastic and holds shape/position better. Also as I'm sure you know it's nice to have an abundance of wire just in case!

One important piece of advice: if you go the Suvalley route, make sure to use the diode rectifier (parts included) and not the supplied tube, which can barely handle the voltage. 

In summary, I've been running the Sunvalley for a couple of weeks now and absolutely love it. My initial intention was to buy a Sun Audio from Devin T, maybe even go to New York and build it in one of his workshops, but I got tired of waiting for the next drop. The man is clearly in demand (good for him!). I've rolled some different 300b's in the Sunvalley, and currently have some Shuguang black treasures in there...simply luscious sounding. Also using a pair of RCA clear top 12AU7s and a Mullard 10M gold pin 12AT7. I'm happy as a clam, even though there's a lot of tube burn-in yet to go.

Overall I'd say that the project isn't as complicated as it's made out to be. Especially if you take your time and get fussy with it, it's a pleasure to build (even twice). Victor is also extremely helpful and friendly. I recommend the experience. 

My pleasure! Regarding speakers, I’m using open baffles made by Caintuck Audio. I chose the Lii Audio F12 full-range drivers, which are about 96dB sensitive. I also have two Caintuck subwoofers with Eminence Alpha 15’s in them.  

One thing I should add about these amplifiers. The Sunvalley, and I presume the Sun Audio, are Japanese appliances that are not grounded in the same way that that US appliances are grounded. They use 2-prong power inlets and power cords instead of our standard 3-prong power inlets and cords. So I understand it, it's because Japanese engineers approach safety measures differently, focusing more on preventing short circuits than ground issues.

However you feel about the relative safety of floating grounds, they can be noisy, susceptible to electromagnetic interference. And indeed my unit was, probably  because I set it in a spot in the house near all our wifi/router gear. Because the soft, static noise I was hearing didn't go away completely when I turned the volume all the way down, it was clear I had a grounding problem. After checking all my ground connections for cold solders and bad connections, I decided to earth-ground the unit, which was quite easy to do. 

Anyone who decides to build the Sunvalley will see in the build guide that all the ground wires connect to a central ground which is, not surprisingly, a through-the-case screw by the rectifier that holds down one of the terminal strips (it's marked "ground point" on page 8 of the illustrated wiring guide). That screw simply needs to be connected by wire to the third prong of a replacement US-style power inlet. Happily, those inlets very easy to acquire, indeed the product linked below is an exact duplicate of the two-prong inlet that comes with the Sunvalley. The screw holes even match up.

All you need to do is install the inlet, connect the internal power leads to the usual spots, then connect the inlet's third-prong ground to the ground point (the US version even includes wire and spades if you want.) The process takes about five minutes.

Anyway, earth-grounding the unit solved my noise problem, and I expect it would solve similar problems for other Japanese amplifiers. Plus in the end you have, at least IMO, a safer amp. Here is the product I mentioned: