08 October, 2014
The glass 6SJ7 is physically and sonically head and shoulders above its metal counterpart. Click pic to enlarge.
Brook Model 7 Mono Preamplifier, Part II: 6SJ7, VT116
This brief follow-up to the main article (Part I) documents the benefit of changing a single tube.
It is unlikely in the near future I'd be able to test out the Brook 7's phono section, so I should first focus on improving the line section, which uses 1 x 6SJ7 (V3) and 2 x 6C4 (V4, V5) and seems to be an anode follower (hence better to avoid long interconnects).
6SJ7/VT116 This is an old tube used by some US amps. my experience with this vintage tube partly stems from my love for the Japanese ICL/Softone (current website). Before ICL turned into Softone they had produced a 300B amp and a similar 2A3 amp which utilize a pair of 6SJ7 (came with stock metal tubes). By chance I acquired a large pile of old glass (GT) VT116/6SJ7, mostly Tungsol's. The difference was night and day. As is usually the case in metal vs glass tubes, the glass tubes are more transparent, harmonically rich and dynamic. And so it proves too in the Brook Model 7! Control over dynamics is improved to such an extent that I was actually overwhelmed by the performance of this Rite of Spring!
A major success! Next stop, Part III, shall be 6C4, which will take a lot longer...