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Philips Miniwatt 12AX7 ECC83 Matched Pair Original Boxes - Holland 1964 I65 -NOS

Philips Miniwatt 12AX7 ECC83 Matched Pair Original Boxes - Holland 1964 I65 -NOS

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Philips Miniwatt 12AX7 ECC83 Matched Pair in Original Boxes - Holland 1964 - NOS

Tube Summary

The "textbook Heerlen sound" has been referenced in several Soundlumia ECC83/12AX7 listings, and many tube enthusiasts asked what all that means. So here 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. 

Sound Characteristics 

The most distinctive sound feature of the Heerlen ECC83'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 and structured. Bass is incredibly deep but well controlled and feels as accurate as on the high end German ECC83's (Siemens, Telefunken, Valvo etc.) We would recommend these as an excellent choice if you are seeking the high end ECC83 tubes that can deliver the legendary Philips house sound flawlessly. 

Professional Tube Testing

Both tubes tested Strong NOS (110%+ nominal mutual conductance) and tightly matched on a reliable and recently calibrated Mercury 2000 tube tester with the following results for mutual conductance:

Tube 1: 1,080/1,090 (108%/109%)
Tube 2: 1,180/1,200 (118%/120%)

Good tubes start at 700 and new tubes (incl. NOS/NIB) 1,000, and the Mercury 2000 tester's rated mutual conductance (nominal) for new tubes is 1,000. Test results can be seen in the pictures. In case you wonder what all these numbers mean to your sound experience, it's actually quite straightforward: mutual conductance directly translates to tube's ability to amplify sound, so the higher these numbers the stronger. No short, leakage or gas.

Appearance & Cosmetic condition

This pair stands out aesthetically among the vintage tubes. At least 90% of the silkscreen is well preserved and the acid-etched Heerlen date codes are perfectly visible on both tubes:

delta 4I2 (delta = Heerlen, 4 = 1964, I = September, 2 = Week 2 of the production month)
delta 4C4 (delta = Heerlen, 4 = 1964, C = March, 4 = Week 4 of the production month)
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