12AX7 / ECC83 TOSHIBA Long Gray Plate Halo Getter Low-Noise Microphone Tube 1960s

12AX7 / ECC83 TOSHIBA Long Gray Plates Halo Getter Tube Made in JAPAN 1960s

AMPLITREX Tested – Red Dot – Low Noise & Microphonics – Vintage Japanese TOSHIBA Production

Test Results:

Tube tested on AMPLITREX AT-1000 Tube Tester:

• Test Conditions: Va = 250V ; Vg = -2V
• 100% Average: Gm = 1600 ; Ia = 1.2 mA
• Test Result: VERY STRONG

Tube:

• Section 1: Gm = 1700 ; Ia = 1.3 mA
• Section 2: Gm = 1500 ; Ia = 1.0 mA

Description:

Selected vintage specimen of 12AX7 / ECC83 Toshiba, attributed to Japanese production from the 1960s based on construction characteristics. The tube features the characteristic Long Gray Plates with Halo Getter configuration, accompanied by a distinctive internal structure and the recognizable top in red glass. An interesting specimen of the Japanese thermionic tradition, intended for audiophiles and musicians seeking vintage tubes with documented electrical characteristics and a particularly careful selection in terms of noise.

Measurements carried out with Amplitrex AT-1000 show VERY STRONG emission, with transconductances of 1700 and 1500 µmhos in their respective sections, corresponding to 106.25% and 93.75% of the nominal reference of 1600. The average therefore reaches 1600 µmhos, exactly matching the reference value. The anode currents measure 1.3 and 1.0 mA respectively, with an average of 1.15 mA, very close to the nominal reference of 1.2 mA. The two sections show an appreciable electrical difference, clearly documented by the measurements, while both maintain fully valid performance.

The tube has passed 48 hours of burn-in and stability testing, maintaining a very strong and even emission, without fluctuations, short circuits, or the presence of gas. A particularly significant element is represented by the extremely low microphonics, confirmed by the special Red Dot selection. This characteristic makes the specimen particularly interesting for the most sensitive audio stages, in which silence and stability are fundamental requirements.

The 12AX7 / ECC83 Long Gray Plates find application in hi-fi preamplifiers, compatible phono stages, and guitar amplifiers, especially in the input and signal amplification stages. Given the electrical difference between the two sections, this specimen is not recommended for phase inverter circuits or applications requiring strict balance. Vintage Japanese thermionic production is traditionally appreciated by audiophiles for a musical presentation generally described as detailed, balanced, and dynamic, with good articulation of the midrange and a pleasant tonal naturalness.

The value of this specimen lies in the Long Gray Plates construction, in the very strong electrical performance and, above all, in the Red Dot selection with extremely low microphonics. Although the original screen printing states Made in Holland, the construction characteristics lead to attributing the tube to Japanese Toshiba production. The absence of a decipherable manufacturing code does not, however, allow us to document its exact origin and year. The well-preserved markings and very good aesthetic condition complete an interesting vintage specimen, carefully tested and selected, for those seeking a vintage 12AX7 with documented performance, verified stability, and extremely low noise.

Condition:

• Condition: Vintage Tubes - Tested and perfectly functioning. Supplied in our custom box for optimal protection. 
  
• Functionality: Perfectly operational.
  
• Aesthetic condition: Very Good – Markings clearly legible with slight signs of age. See photos for details.
  
• Special selection: Red Dot, with low noise and microphonics verified using Amplitrex AT-1000.
• Manufacturing Code: Code not decipherable. Although the screen printing states Made in Holland, it is clearly a production attributable to TOSHIBA Japan, approximately from the 1960s based on the construction characteristics.

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