These are the desirable low-noise versions produced at the Heerlen, Holland factory. • Etchings: Delta 0B4 and Delta 0B3 (sought-after Heerlen plant date codes). These are stronger-testing tubes with excellent balance between triodes.
Item Tag: 12AX7s
Rare Amperex 12AX7s, Electronics For Medicine, Matched Stronger Test Heerlen Hol
These are the desirable low-noise versions produced at the Heerlen, Holland factory. • Etchings: Delta 0B4 and Delta 0B3 (sought-after Heerlen plant date codes). These are stronger-testing tubes with excellent balance between triodes.