Is there a strategy in preamp tube placement?

@pindac 

I was one of the early buyers of Linlai's 6SN7. Due to a lack of information at the time, I purchased E-6SN7's from an Ebay dealer. I was very active on that thread as members learned that there were indeed two different 6SN7 types (as stated on the Linlai website). As the tubes burned in, it sounded like they may live up to the hype. But after 100 hours they sounded dull and lacked the realism that the Grant Fidelity tube users were reporting. 

If I knew then what I know now, I would have paid the higher price of the Global Elite with the vertical Linlai logo on the glass.

I settled on the KR Black Glass VT 231, as the best attractor for myself.

I then learned of certain individuals making claims the Linlai E 6SN7 with approx’ 100 Hours usage life has compared favourably to the KR VT 231. The reports being made on these Tubes are generally good and have got my attention.

@pindac , the Linlai Global Elite E-6SN7 are the tubes being praised and compared to Ken Rad VT-231. Available only through Linlai factory direct and Grant Fidelity.

The E-6SN7 available on Ebay are intended for the Chinese market. The Global Elite are for export to the US.

@xcool

I own two pairs of Ken Rad VT-231 black glass and a pair of clear glass (1945). When purchasing these tubes or others from the 40’s, it’s imperative that the dealer offers testing for noise and microphonics. Andy from VTS, Kevin Deal, Brent Jessee (for a fee) all noise-test their tubes. But there’s no way to tell if a tube will become microphonic at some point in its lifetime. All three pairs of my KR’s have remained noise free. But one of my beloved Tung-Sol BGRP’s went microphonic after 3 years. I've been using these tubes in gain stages of my preamp and amp.

@xcool 

The noise testing service is somewhere on the Brent Jessee site, $10/pair I think. You have to request it in your email to him.

With 6SN7s from the 40's or 50s, I always order noise testing. In Brent's description he may say a certain tube is low-noise, then it's not necessary to pay an extra fee. As @mulveling stated, later generations of tubes used different internal designs to mitigate microphonics. Some military-grade tubes are "ruggedized" with extra support rods and micas to withstand shock and vibration. With 6SN7s, there's a chance these tubes may be less microphonic.