รมดำแล้วเสียงดีขึ้นมั้งครับ
What's with the "smoked" glass? Most 6SN7GTs made through the early 1950s had a graphite coating on the inside surface of the glass bulb. This served to drain excess accumulations of electrons that could affect the operation of the tube. Why this was dropped isn't clear, but probably was due both cost-cutting and the use of a different type of glass that was not prone to electron accumulation.