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HP Select Amperex 12AU7 ECC82 Preamp Tube - Holland 1966 - Tests Strong

HP Select Amperex 12AU7 ECC82 Preamp Tube - Holland 1966 - Tests Strong

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Perfectly balanced vintage HP Select Amperex 12AU7 tube - Heerlen sound from 1966 - Tested Strong - Very Rare

Product Summary

These are the legendary "medical tubes" made by Amperex Holland for Hewlett-Packard's medical devices distributed around the world. Each tube had to go through rigorous test and selection processes designed, implemented and monitored by HP. What you get is the best from the best candidates in build quality and low noise. Manufactured and released only in limited quantity, these tubes are elusive to find and remain top choices of serious listeners and tube enthusiasts. 

Sound Qualities

Despite the HP label, you get the "textbook" Amperex Holland midrange presentation that is transparent, natural and expansive, with a slight touch of warmth that illuminates your musical world. The top end is super airy, smooth and nicely extended like one would expect from the best Siemens tubes. Vocals are intimate, sweet and forward (but not right in your face) and that always reminds me how the vocals sound on the best Mullard tubes. Bass is deep and well controlled and the accuracy feels very similar to the high end German 12Au7/ECC82 tubes (Siemens, Telefunken etc.) 

Professional Tube Testing 

Slightly below NOS, This pair tested Very Strong (95% - 99% nominal mutual conductance) on a Mercury 2000 tube tester with the following result (mutual conductance in uMhos): 2,900/2,930 (or 97%/98% of nominal)

Good tubes start around 2000 and new tubes (incl. NOS/NIB) 3,000, and Mercury 2000's rated mutual conductance (nominal) for new tubes is 3,000. Test result can also be seen in the pictures. In case you wonder what all these numbers would mean to your sound experience, it's actually quite straightforward: mutual conductance directly translates to tube's ability to amplify sound so the higher the numbers the stronger. 

Appearance & cosmetic condition

We treasure this tube also because of its great cosmetic condition of both tubes - over 95% of the paint is intact and well preserved. The Heerlen factory date code etched on glass is perfectly visible: delta 6A2 (delta = Heerlen, 6 = 1966, A = January, 2 = 2nd week of the month) 
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