I remembered that I have had this Allo audio Boss 2.1 DAC (I originally bought it to use the as DAC + digital cross over but then i bougth a full-on active cross over) for some time and I had forgotten about it, now that it is slim pickings in my digital front end arsenal I decided to use them so i did some hours of listening with this DAC as source and I think it is garbage and sounds no better than any run of the mill Sabre DAC (sounding thin and fatiguing because high freuencies just sound wrong, thin and lit up, metallic, digital) but here goes
so far among all the 6J1 equivalents that I have tried the biggest disappointment, and confusingly so, have been the Yugoslavia 6HM5 also known as EC900 made by Ei
I say confusingly because they have a reputation for soft tubey and gooey sound and what I am hearing is the exact opposite. These were supposed to be big on euphonics and based on this reputation I was expecting these to end up being my favorites. This is the kind of sound that I actually like. I am always happy to sacrifice resolution and extension for some warm forward midrange and attack and transients for some sweet lush (even at the cost of it being somewhat muted) top end. Didnt really work out though.
first is that these are THE most microphonic tubes that i have ever heard. it is incredible even if a spec of dust lands on them i will hear it amplified. every vibration (this got a little better after a few hours). they sound thin and metallic. the mid range is just off, tonally they are my least favorite. maybe they need more time burning in..
on the other hand the cheap Russian Voskhod 6J1P-EVs known for the rocket logo on them have been the most pleasant surprise and they have a very well rounded and decidedly "Hifi" sound. with detailed extended airy top octaves and real nice impactful bass. I of course prefer the more full bodied thicker mid range that the WE403 did but I think most my audiophile friends will probably choose the Russian as the more accomplished one.