Hi, Jadis, sorry for late responce.
I did do some searching on web before I reply you(lukily I found some articles about 6SN7 also wrote by you...haha), according to yor suggestion, you mentioned that I could try replace two of the default 6SN7 by GP CV 181A and try the result of different positions, I am wondering if I replace all four 6SN7 of my Melody Super34 by GP CV 181A, what will happen??
Jadis 兄,
I find a pair from foreign website as following, and the price is not expensive, USD 295 per pairs excluded shipping.
However, there is no photo given so I am not so sure is that the pair you introduced, could you feel free to have a look and advise, thank you.
Quote
"12AU7 Mullard longplates, square getter, 1950s vintage, Great Britain. VERY RARE.
New Old Stock White Box and original box. Some shield logo types, some are the old white label pre- shield logo version. These are all the older long narrow plate version, with the rare early SQUARE top getter, with the 1950s date code. These are incredible tubes with a fine soundstage, clean top end with a touch of midrange warmth. Rare. Good stock now but fast vanishing!! MATCHED PAIRS, ARE $295.00 PER PAIR."