Sun Valley vs Sun Audio 300b

@kdogsy I found a few things.

- YouTuber and DIYAudio poster Skunkie built the Sun Audio and found a lot of things she considered problems. Paraphrasing here - the input stage of how the twin triodes are wired is very very high gain and increases noise and distortion. She wired them in a different way for a much better and cleaner sound. It’s possible the original design was done this way intentionally, and I know OJAS is selling the "history" of the amp, but she questioned the original 6SN7 schematic and did not agree it sounds best. The design was thought to be from JC Morrison but someone else claimed it was a Japanese guy. I was interested in trying Skunkies schematic if I build it.

-I asked Brent Jesse and he considers both the 12AU7 and 6SN7 to be the best twin triodes for different reasons, and he said 12AU7 is lower noise and FAR more available. (Telefunken smoothplates, etc). A great 6SN7 is really hard to find right now and collectors bought them all up. If you plan on maxing out the amps, it’s something to consider.

- One think Skunkie did not like about the Sun Audio design is the 300b plate voltage is strangely low, around 300V. Her mod puts it near 400 which is the modern day common use.

- I asked Victor about removing the negative feedback on Sun Valley and he did not give a clear answer. It seems Sun Valley is designed for a "modern" 300b sound, more stable, a bit more circuitry. The Sun Audio with Skunkie’s mods may compete with it, but it also has a double starting price for the kit and you need to find good 6SN7’s.

- From what I read, Hashimoto transformers may give me the sound I prefer, which is a bit of Japanese Furutech sound, kind of OCC copper sound, very realistic and intimate.

I will likely buy the Sun Valley from Victor and try it with and without the GNF. I plan to upgrade all components to the best Audio Note, VCap and internal wiring, so I don’t think I will be disappointed. It’s impossible to know for sure, but gotta start somewhere. :)

@clustrocasual amazing thanks for the detailed reply. I will try and learn some from Skunkie’s work on the Sun Audio. 
There seems to be more awareness about the Sun Audio amp I guess maybe because it’s been around for longer in its current form. 
I get the feeling the Sun Valley may not have had the Hashimoto as standard for as long. 
 

Out of curiosity what is wrong with GNF?. Is it considered a less pure design as in if it was a better circuit it shouldn’t need it ? 
 

I've gone back and forth on the Sun Audio. It is true that simpler circuits are _not always_ better and I think it came from the hazy days of japanese jazz kissas. think NOS speaker cabling, WE , Beldon etc. Those are all fine, but not really what I've been building in my own systems. I prefer things a bit more modern. 

I looked at AN's 300B's going back a couple decades. I couldn't see all the schematics but they are not as simple as the Sun Audio and they moved away from 6Sn7. But AN and everyone else says, why bother running 300b in NF... I agree, makes no sense in single ended design. Rather, put higher quality components in. Before I buy I may as the question on Victor's DIYAudio thread.

Also, I have an idea to sandblast and paint the SV chassis, so I'm a bit up to the challenge. 

Also, I agree SV maybe new to Hashimoto - and it might mean this is a good opportunity! I did ask Devon on his OJAS instagram which transformers he preferred (Tamura versus Hashimoto) and he gave a waffling answer :). Hmmm he has to support SV, after all.