I have been fairly busy with the Big 7/300B topic for a little while now after getting the OK from Lukasz himself about experimenting with them about a month ago. I had mentioned how I liked the 300B tube in former amps over the years and he told me "It should be fine" to try it on my B7 with the switch set to the 2A3 position.I happened to have a "leftover/used" pair of Electro Harmonix 300B's from an amp I had sold awhile ago (I sold it with the Sophia Ceramic Base Gold Pins) and I found the 300B's a refreshing breath of air to my entire presentation. Compared to my Sovtek 2a3's (which were the first tubes I used when I received it) my B7 was more full bodied and much more fleshed out...tonal shadings were more defined and the "tangibility factor" was more apparent. At the time I was using the Shuguang 274B rectifier. Swapping the Shuguang for a NOS "National Union" 5u4 wasn't much more than a lateral move and I am temporarily back to the Shuguang while looking forward to trying an EM Lab 5u4G Mesh plate...
Meanwhile, for me, the big news for "The Big 7" is the topic here... my exuberance over the brand new Sophia 2.5v 300B Carbons I installed 2 days ago. In a word: WOW. Again: WWOWW!
I can't believe that this dac had ANY more room for improvement and it keeps shocking me every time I do something "nice" for it! Whether it's a power cord designed for digital (see some earlier posts on the TWL Digital American), some sort of superior vibration isolation (I use Sistrum Stands to great effect) or the most obvious choice: premium tubes...this Dac never ceases to truly amaze me.
Sophia Carbons brought : Deeper, richer tones; deeper, wider soundstage; perfect timing/pace of each notes' "attack and decay"...highs drifted or sparkled and bass rumbled or slammed...and all the while my system just said "Do me, I'll keep up...!".
The friend who recommended them said the difference between the EH's and Sophia Carbons will be like a chevy sedan and a Porsche 911 turbo. He was right.
So, YES, try your favorite 300B's and share your thoughts here. But mostly just enjoy your time in the sweet spot...listening just keeps getting better and better and better..... Happy Lissn'n, Lissnr