12AU7 / ECC82 RCA Black Plates AMPLITREX Matched Pair Square Getter Made in USA '56

12AU7 / ECC82 RCA Black Plates AMPLITREX Matched Pair Square Getter Made in USA '56

Low Noise & Microphonics – STRONG - Vintage RCA Production

Test Results:

Tube tested on AMPLITREX AT-1000 Tube Tester:

• Test Conditions: Va = 250V ; Vg = -8.5V
• 100% Average: Gm = 2200 ; Ia = 10.5 mA
• Test Result: STRONG

Tube #1:

• Section 1: Gm = 1600 ; Ia = 8.2 mA
• Section 2: Gm = 1900 ; Ia = 9.0 mA

Tube #2:

• Section 1: Gm = 1600 ; Ia = 7.8 mA
• Section 2: Gm = 1800 ; Ia = 8.8 mA 

• Burn-in / Stability Test: 48h – OK
• Microphonics: Low. Tested and suitable for use in hi-fi equipment and guitar amplifiers, even in the most sensitive audio stages.
• Noise: Low and well-controlled. Silent operation in hi-fi and musical amplifiers in designated positions.
• Balance: The sections are not perfectly aligned. The tube is suitable for use in hi-fi in non-critical stages (input or driver) and in guitar amplifiers. Not recommended as a phase inverter or in applications requiring strict balance between sections.
• Emission Quality: Strong – Strong and regular emission, suitable for any application.
• Shorts and GAS: Absent.

Description:

Precious Matched Pair of 12AU7 / ECC82 RCA, authentic American production Made in USA from 1956, characterized by the sought-after Black Plates with Square Getter construction. A typical configuration of early RCA 12AU7 family productions and particularly interesting for those seeking the character of 1950s American tubes in a carefully selected and tested pair.

The manufacturing code 6-09 places both units in the 9th week of 1956 and identifies production by Radio Corporation of America, Camden, New Jersey. The origin from the same production period, along with the Black Plates / Square Getter construction, adds further technical and collector's interest to the pair.

The tubes have been carefully tested in our laboratory using an Amplitrex AT-1000 Tube Tester, achieving a STRONG classification. Tube #1 measures Gm 1600/1900 with Ia 8.2/9.0 mA, while #2 measures Gm 1600/1800 with Ia 7.8/8.8 mA. The values show good overall consistency between the two units, allowing them to be offered as a Matched Pair, with strong, regular, and stable emission.

Both have passed a 48-hour Burn-in / Stability Test and have been selected for Low Noise & Microphonics, with low and well-controlled noise. They are therefore particularly interesting for hi-fi preamplifiers, input and driver stages, as well as for guitar amplifiers and other compatible equipment where quietness and stability are important parameters.

The individual internal sections are not perfectly aligned; for this reason, the pair is not recommended for applications such as phase inverters or for circuits requiring strict symmetry between the two triodes. This does not limit their use in the numerous 12AU7 applications where absolute section balance is not a fundamental requirement.

Sonically, 1950s RCA Black Plates 12AU7 are particularly appreciated for a full-bodied, natural, and musical presentation, with rich and well-structured mids, solid and well-controlled bass frequencies, and a soft but defined high range. A typically American character that offers musicality and listening pleasure without sacrificing detail and dynamics.

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