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RCA

6SN7GT / VT-231 RCA Radiotron Smoked Glass Matched Pair Silver Logo Black Plates Foil Getter AMPLITREX Tested Low Noise Tubes

6SN7GT / VT-231 RCA Radiotron Smoked Glass Matched Pair Silver Logo Black Plates Foil Getter AMPLITREX Tested Low Noise Tubes

¥1,517.00 CNY
¥1,517.00 CNY
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6SN7GT / VT-231 RCA Radiotron Smoked Glass Matched Pair Silver Logo Black Plates Foil Getter - Made In USA - 1940s

AMPLITREX Tested – VERY STRONG – Low Noise & Microphonics

Test Results:

Tubes tested on Amplitrex AT-1000 Tube tester:

  • Test Conditions: Va = 250V, Vg = -8V
  • Average 100% Gm = 2600 ; Ia = 9.0 mA
  • Test Result: VERY STRONG

Tube #1

  • Section 1: Gm = 2600 ; Ia = 9.6 mA
  • Section 2: Gm = 2500 ; Ia = 8.0 mA

Tube #2

  • Section 1: Gm = 2400 ; Ia = 7.2 mA
  • Section 2: Gm = 2500 ; Ia = 8.3 mA

Description

Extremely rare vintage pair of 6SN7GT RCA Radiotron Smoked Glass, made in the United States and carefully selected as a Matched Pair. The set includes one JAN CRC-6SN7GT / VT-231 and one JAN 6SN7GT, both featuring the same construction configuration: Black Plates with Foil Getter and smoked glass. This particular RCA version, now difficult to find, is among the most sought after by enthusiasts of early American 6SN7GT tubes. The original military markings and unmistakable internal architecture attest to its authenticity and historical appeal.

Measurements taken with the Amplitrex AT-1000 show a transconductance between 2400 and 2600 µmhos, with averages of 2550 and 2450 µmhos for the respective tubes, close to the nominal reference of 2600. The anode currents range from 7.2 to 9.6 mA, with averages of 8.8 and 7.75 mA respectively, compared to the reference of 9.0 mA. The results confirm good consistency of the average transconductances, while highlighting some differences in anode currents and the balance of the individual sections.

Both tubes have been subjected to careful instrumental checks that confirmed very strong and stable emission, without fluctuations, short circuits, or gas presence. Noise and microphonics checks also yielded low results, an aspect that is particularly important for vintage tubes of this type, also intended for sensitive audio applications.

The 6SN7GT RCA Black Plates Smoked Glass are particularly appreciated in headphone amplifiers, hi-fi preamplifiers, and compatible driver stages. Historic RCA productions with black plates have traditionally been sought by audiophiles for a musical presentation generally described as full-bodied, refined, and natural, with a rich midrange full of nuances, a pleasant expressive depth, and an engaging musical reproduction.

The value of this extremely rare RCA pair lies above all in the particular construction Smoked Glass with Black Plates and Foil Getter, shared by both specimens. Although the different manufacturing markings, 7-52 and H3E, do not allow us to establish with certainty that the two tubes belong to the same year of production, their construction characteristics are consistent, from the structure of the plates to the configuration of the getter. Two authentic vintage American tubes, with original markings, very good cosmetic condition, and documented electrical characteristics. A combination of rarity, historical authenticity, and instrumental selection, intended for enthusiasts who wish to own and use one of the most fascinating creations of the RCA thermionic tradition.

Additional tests:

  • Microphonics and noise: Low. Tested and compliant for use in hi-fi equipment and guitar amplifiers, including the most sensitive audio stages.
  • Balance: Good. The sections show a consistent balance, fully compatible with use in hi-fi and musical amplifiers, in all applications where absolute symmetry between the sections is not required.
  • Emission: Excellent – Very strong and stable emission, without fluctuations.
  • Short circuits / Gas: absent

Condition

  • Condition: Vintage Tubes - Tested and perfectly functioning. Supplied in our custom box for optimal protection.
  • Functionality: Perfectly operational
  • Cosmetic condition: Very Good – Markings clearly legible with slight signs of age. See photos for details.

Manufacturing code:

  • 7-52 → RMA/EIA Open Date Code → manufactured in the 52nd week of 1957 - by Radio Corporation of America, Camden, N. J.
  • H3E → Undecipherable code. Production can be attributed approximately to the 1940s based on construction characteristics. The vintage construction, with black plates, bottom foil getter, and smoked glass, is fully consistent with this period.

Discover why our tubes are different →

Terms of Sale & Safety

Sales Terms & Product Safety

Each vacuum tube is carefully selected, tested, and verified in our laboratory before shipment. Where stated in the listing, test results, matching data, and declared characteristics refer to measurements performed using the specified test equipment and operating conditions.

Sound descriptions are provided for guidance only and reflect the characteristics generally associated with that particular tube type. Personal sound preferences, tube rolling, or perceived differences between audio systems do not constitute a product defect.

Before installation, please verify the tube’s electrical and mechanical compatibility with your equipment and follow the manufacturer’s instructions.

New production and NOS tubes are shipped with a tamper-evident security seal and internal technical documentation to ensure traceability of the product’s condition at the time of shipment.

Product Safety (GPSR)

Vacuum tubes are electronic components intended exclusively for use in compatible equipment and must be installed in accordance with the equipment manufacturer’s instructions.

Due to their historical or vintage nature, certain technical specifications may be based on original datasheets or equivalent technical documentation when documentation from the specific manufacturer is unavailable.

Use only with suitable equipment. Keep out of reach of children.

Shipping & Returns

Shipping & Returns

We ship worldwide using carefully selected express carriers and protective packaging specifically designed for vacuum tubes.

If you change your mind, you may exercise your right of withdrawal within 14 days of delivery, where applicable under the relevant consumer protection laws. The product must be returned complete with its original packaging and accessories, in the same commercial condition in which it was received. Return shipping costs are the responsibility of the customer.

Every returned item undergoes a technical inspection. Installation, use, tube rolling, or any other handling may reduce the product’s commercial value and may affect the refund amount, in accordance with applicable law.

If you believe the product has a lack of conformity, our laboratory will carry out the necessary inspections and apply the remedies provided by the applicable consumer protection legislation.

For further details, Customers are invited to consult the “Terms and Conditions” and “Refund Policy” sections of our website, or to contact us before placing an order.

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  • ATTENTION PLEASE

    Please understand that the writing on the glass of vintage valves has become very delicate over the years and comes off easily. You must handle them with extreme care to avoid this. Wear and damage to the writing on the valves reduces their market value and causes damage. Please exercise extreme caution.

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