Soundlumia's Opinion
The "textbook Heerlen sound" has been referenced in several Soundlumia listings of Philips Holland 12AU7/ECC82 tubes, and many tube enthusiasts asked what that all means. So this is the answer: the late 1950s and very early 1960s tone, the beginning of over a decade's excellence in sound, the classic tonal template for all the great (and greater) Amperex/Philips/Valvo/Miniwatt tubes to be made in the years to come, the timeless Philips radio tone that many of us grew up listening to.
The most distinctive sound feature of the Heerlen 12AU7's is the transparent, natural and expansive midrange presentation, with a slight touch of warmth that illuminates your music. Every piece of music you play through these tubes sounds like from a vinyl record, whether your sound source is phono or not. The sound stage is spacious, deep, structured and holographical. Bass is incredibly deep but well controlled and feels as accurate as on the high end German ECC82's (Siemens, Telefunken, Valvo Hamburg etc.) The stellar performance of foil d-getter takes all these wonderful sound qualities to a whole new level: instrument separation is super clean, detail retrieval is surreal, and it goes without saying that the extremely low noise on these tubes is to the vanishing point.
Professional Tube Testing
This set was tested and certified by RoeTest V11 Professional Tube Testing System with the following result:
Tube 1:
Measured transconductance(GM): 1.99/1.95 mA/V - 90%/89% (100% = 2.2 mA/V)
Measured plate current(IA): 9.535/9.287 mA - 91%/88% (100% = 10.5 mA)
Tube 2:
Measured transconductance(GM): 2.11/2.14 mA/V - 96%/97% (100% = 2.2 mA/V)
Measured plate current(IA): 10.015/10.382 mA - 95%/99% (100% = 10.5 mA)
NO shorts, leakage or gas. NO noise or microphonics.
Curve trace is also included in the original RoeTest report.
Appearance & cosmetic condition
Despite some loss of paint, these Bugle Boys are in great condition, which is amazing for 62-year old tubes.
⊿2L2 (⊿ = Heerlen, NL, 2 = 1962, L = December, 2 = Week 2 of production month)
⊿2L3 (⊿ = Heerlen, NL, 3 = 1963, L = December, 2 = Week 2 of production month)
Packaging
NEW white tube boxes.
